International Glossary of Biochemistry, Construction, Energy & Power Engineering

First Edition, 2009

ISBN 978 93 80168 77 7

© All rights reserved.

Published by: Global Media 1819, Bhagirath Palace, Chandni Chowk, Delhi-110 006 Email: [email protected]

Table of Contents 1. Power Engineering Glossary 2. Biochemistry Glossary 3. Construction Glossary 4. Energy Glossary

ABMA - American Boiler Manufacturers Association. ABRASION - The wearing away of a surface by rubbing, as with sandpaper on wood. ABRASION RESISTANCE - The ability of a material to resist surface wear. ABRASIVE EROSION - Erosive wear caused by the relative motion of solid particles which are entrained in a fluid, moving nearly parallel to a solid surface. ABSOLUTE HUMIDITY - Amount of moisture in the air, indicated in kg/kg of dry air. ABSOLUTE PRESSURE - Total pressure measured from an absolute vacuum. It equals the sum of the gauge pressure and the atmospheric pressure corresponding to the barometer. ABSOLUTE PRESSURE - Air at standard conditions (70°F air at sea level with a barometric pressure of 29.92 in Hg) exerts a pressure of 14.696 psi. This is the pressure in a system when the pressure gauge reads zero. So the absolute pressure of a system is the gauge pressure in pounds per square inch added to the atmospheric pressure of 14.696 psi (use 14.7 psi in environmental system work) and the symbol is "psia". ABSOLUTE TEMPERATURE SCALE - A scale of temperature measurement in which zero degrees is absolute zero. ABSOLUTE VELOCITY - The vector sum of the velocity of a fluid parcel relative to the earth and the velocity of the parcel due to the earth's rotation; the east-west component is the only one affected. ABSOLUTE ZERO - A hypothetical temperature at which there is total absence of heat. Since heat is a result of energy caused by molecular motion, there is no motion of molecules with respect to each other at absolute zero. It is theoretically the coldest possible temperature. ABSOLUTE ZERO TEMPERATURE - Temperature measured from absolute zero (-459.67°F, or -273.16°C). ABSORBENT - A material which, due to an affinity for certain substances, extracts one or more such substances from a liquid or

gaseous medium with which it contacts and which changes physically or chemically, or both, during the process. Calcium chloride is an example of a solid absorbent, while solutions of lithium chloride, lithium bromide, and ethylene glycols are liquid absorbents. ABSORBER - That part of the low side of an absorption system, used for absorbing vapor refrigerant. ABSORPTION - A process whereby a material extracts one or more substances present in an atmosphere or mixture of gases or liquids accompanied by the material's physical and/or chemical changes. ABSORPTION REFRIGERATION SYSTEM - One in which the refrigerant, as it is absorbed in another liquid, maintains the pressure difference needed for successful operation of the system. ABSORPTION REFRIGERATOR - Refrigerator that creates low temperatures by using the cooling effect formed when a refrigerant is absorbed by chemical substance. ABSORPTION SYSTEM - A refrigeration system in which the refrigerant gas evolved in the evaporator is taken up in an absorber and released in a generator upon the application of heat. ABSORPTION TOWER - A tower or column, which effects contact between a rising gas and a falling liquid, so that part of the gas may be taken up by the liquid. ACCELERATION - The rate of change of velocity, as a function of time. Expressed in m/s. ACCELERATION DUE TO GRAVITY - The rate of increase in velocity of a body falling freely in a vacuum. Its value varies with latitude and elevation. The International Standard is 32.174 ft. per second per second. ACCELERATION PERIOD - In cavitation and liquid impingement erosion, the stage following the incubation period, during which the erosion rate increases from near zero to a maximum value. ACCELERATION - The time rate of change of velocity; i.e., the derivative of velocity; with respect to time.

ACCEPTABLE WELD - A weld that meets all of the requirements and the acceptance criteria prescribed by the welding specifications. ACCESSIBLE HERMETIC - An assembly of motor and compressor, inside a single bolted housing unit. ACCUMULATOR - Storage tank which receives liquid refrigerant from evaporator and prevents it from flowing into suction line before vaporizing. ACETONE - A filler added to acetylene cylinders, capable of absorbing 25 times its own volume of acetylene. ACID - Literally hitter, but chemically the state of a water solution containing a high concentration of hydrogen ions. ACID ATTACK - Caused by an incomplete flushing after an acid cleaning process of boilers or similar equipment. ACID CLEANING - The process of cleaning the interior surfaces of steam generating units by filling the unit with dilute acid accompanied by an inhibitor to prevent corrosion and by subsequently draining, washing, and neutralizing the acid by a further wash of alkaline water. ACID CONDITION IN SYSTEM - Condition in which refrigerant or oil in a system, is mixed with vapor and fluids that are acidic in nature. ACID EMBRITTLEMENT - A form of hydrogen embrittlement that may be induced in some metals by an acid. ACID GAS - A gas that that forms an acid when mixed with water. In petroleum processing, the most common acid gases are hydrogen sulfide and carbon dioxide. ACID RAIN - Atmospheric precipitation with an pH below 5.6 to 5.7. ACID SOAK - A method of acid cleaning, in which the acid is pumped into the boiler and rests there for a period of time. ACIDIC - The reaction of a substance with water resulting in an increase in concentration of hydrogen ions in solution (see acid).

ACIDIFIED - The addition of an acid (usually nitric or sulfuric) to a sample to lower the pH below 2.0. The purpose of the acidification is to "fix" a sample so it will not change until it is analyzed. ACIDITY - Represents the amount of free carbon dioxide, mineral acids, and salts (especially sulfates of iron and aluminum) which hydrolyze to give hydrogen ions in the water. The acidity is reported as millie equivalents per liter of acid, or ppm acidity as calcium carbonate, or pH, the measure of hydrogen ion concentration. ACOUSTIC - A term pertaining to sound, or the science of sound. ACROSS THE LINE - A method of motor starting, which connects the motor directly to the supply line on starting or running. ACTION - Refers to the action of a controller. It defines what is done to regulate the final control element to effect control. ACTIVATED ALUMINA - Chemical which is a form of aluminum oxide. It is used as a drier or desiccant. ACTIVATED CARBON - Is a specially processed carbon, used as a filter drier. Commonly used to clean air. ACTIVATED SLUDGE - An aerobic biological process for conversion of soluble organic matter to solid biomass, removable by gravity or filtration. ACTIVE STORAGE PILE - A method of stockpiling coal, sometimes called live storage. The pile is located outside the plant but adjacent to it, and usually contains four or five days of operating supply. The pile is not compacted, as it is not stored long enough to be exposed to the hazard of spontaneous combustion. ACTUATOR - The portion of a regulating valve, which converts mechanical, fluid, thermal, or electrical energy; into mechanical motion to open or close the valve seats or other such devices. ADIABATIC - Occurring with no addition or loss of heat from the system under consideration. ADIABATIC CHANGE - A change in the volume, pressure, or temperature of a gas, occurring without a gain of heat or loss of heat.

ADIABATIC COMPRESSION - Compressing a gas without removing or adding heat. ADIABATIC COOLING - A method in which paramagnetic salts are precooled, and then demagnetized, thereby producing further cooling. ADIABATIC EFFICIENCY -The ratio of actual work output of a heat engine to the ideal output. ADIABATIC EXPANSION - The expansion of a gas, vapor, or liquid stream from a higher pressure to a lower pressure, with no change in enthalpy. ADIABATIC PROCESS - A thermo-dynamic process in which no heat is extracted from or added to the system of the process. ADIABATIC SATURATION PROCESS - A process to determine absolute or relative humidity. ADJUSTABLE DIFFERENTIAL - A means of changing the difference between the control cut-in and cutout points. ADJUSTABLE RESISTOR - A resistor whose value can be mechanically changed, usually by the use of a sliding contact. ADSORBENT - A material which has the ability to cause molecules of gases, liquids or solids to adhere to its internal surfaces without changing the adsorbent physically or chemically. In water treatment, a synthetic resin possessing the ability to attract and to hold charged particles. ADSORPTION - The adhesion of the molecules of gases, dissolved substances, or liquids in more or less concentrated form, to the surface of solids or liquids with which they are in contact. Commercial adsorbent materials have enormous internal surfaces. ADSORPTION INHIBITORS - They are materials which caused them to be adsorbed on to the metal surface due to their polar properties. ADVECTION - The transfer of heat by horizontal movement of air. AERATION - Exposing to the action of air, like blowing air through water before discharging to a river.

AERATION CELL - (see oxygen cell) AEROBIC - A condition in which "free" or dissolved oxygen is present in water. AERODYNAMIC NOISE - Also called generated noise, self-generated noise; is noise of aerodynamic origin in a moving fluid arising from flow instabilities. In duct systems, aerodynamic noise is caused by airflow through elbows, dampers, branch wyes, pressure reduction devices, silencers and other duct components. AGGLOMERATE - The clustering together of a few or many particles into a larger solid mass. AGITATOR - A device used to cause motion in confined fluids. AIR - A substance containing by volume approximately 78 - 79% nitrogen; 20.95% oxygen, .94% argon, traces of carbon dioxide, helium, etc. AIR BLAST TRANSFORMER - A transformer cooled by forcing a circulation of air around its windings. AIR CAPACITOR - Is a capacitor, which uses air as the dielectric between the plates. AIR CHANGES - A method of expressing the amount of air leakage into or out of a building or room in terms of the number of building volumes or room volumes exchanged. AIR CLEANER - A devise used to remove air borne impurities. AIR COIL - Coil on some types of heat pumps used either as an evaporator or a condenser. AIR CONDITIONER - They are basically refrigeration devices cooling air and rooms rather then food compartments. AIR CONDITIONER, UNITARY - An evaporator, compressor, and condenser combination; designed in one or more assemblies, the separate parts designed to be assembled together.

AIR CONDITIONING -The process of treating air to simultaneously control its temperature, humidity, cleanliness, and distribution to meet the requirements of the conditioned space. AIR CONDITIONING UNIT - An assembly of equipment for the treatment of air so as to control, simultaneously, its temperature, humidity, cleanliness and distribution to meet the requirements of a conditioned space. AIR CONDITIONING, COMFORT - The process of treating air so as to control simultaneously its temperature, humidity, cleanliness and distribution to meet the comfort requirements of the occupants of the conditioned space. AIR COOLER - A factory-encased assembly of elements whereby the temperature of air passing through the device is reduced. AIR DIFFUSER - A circular, square, or rectangular air distribution outlet, generally located in the ceiling and comprised of deflecting members discharging supply air in various directions and planes, and arranged to promote mixing of primary air with secondary room air. AIR DIFFUSION AERATORS - They are aerators into which air is pumped into the water through perforated pipes, plates, or any other method. AIR DUCT - A tube or conduit for conveying air from one place to another. AIR FLOTATION - A process of accelerating sedimentation, by introducing air into the water, this lowers the density of the water, and increases the differences in the densities of the water and the suspended particles. (DAF), Dissolved Air Flotation. AIR GAP -The space between magnetic poles, or between the rotating and stationary assemblies in a motor or generator. AIR HANDLER - The fan blower, heat transfer coil, filter, and housing parts, of a system. AIR INFILTRATION – The leakage of air into a room through cracks in doors, windows, and other openings. AIR PURGE - The removal of undesired matter by replacement with air.

AIR SATURATED - Moist air in which the partial pressure of the water vapor is equal to the vapor pressure of water at the existing temperature. This occurs when dry air and saturated water vapor coexist at the same dry-bulb temperature. AIR SENSING THERMOSTAT - A thermostat unit, in which the sensing element is located in the refrigerated space. AIR STANDARD - Air having a temperature of (20°C), a relative humidity of 36 percent, and under a pressure of 14.70 PSIA. The gas industry usually considers (16°C) as the temperature of standard air. AIR VENT - Valve, either manual or automatic, to remove air from the highest point of a coil or piping assembly. AIR WASHER - A water spray system or device for cleaning, humidifying, or dehumidifying the air. AIR, AMBIENT - Generally the air surrounding the object. AIR, DRY - Air without contained water vapor. AIR, OUTDOOR - Air taken from outdoors and, therefore, not previously circulated through the system. AIR, RE-CIRCULATED - Return air passed through the conditioner before being again supplied to the conditioned space. AIR, REHEATING - In an air conditioning system, the final step in treatment, in the event the temperature is too low. AIR, RETURN - Air returned from conditioned or refrigerated space. AIRBORNE SOUND - Sound which reaches the point of interest by radiation through the air. AIR-COOLED CONDENSER - Heat of compression is transferred from condensing coils to surrounding air. This may be done either by convection or by a fan or blower. AIR-SENSING THERMOSTAT – A thermostat unit, in which the sensing element is located in the refrigerated space.

ALCOHOL BRINE - A water and alcohol solution, which remains as a liquid below 0°C. ALGAE - A minute fresh water plant growth which forms a scum on the surfaces of re-circulated water apparatus, interfering with fluid flow and heat transfer. Lower form of plant life, usually green and blue green algae appear in cooling water systems. They are responsible for copious amounts of stringy green slime masses. ALIVE - A term referring to a circuit in which a current is flowing. Also referred to as live. ALKALI - A substance having marked basic properties. Applying to hydroxides of potassium, sodium, lithium, and ammonium. They turn red litmus to blue. Includes hydroxides of the alkaline earth metals of barium, strontium, and calcium. ALKALINE - Having a pH greater than 7. ALKALINE BOIL-OUT - Employed to remove oil and grease deposits from heating surfaces. ALKALINITY - An expression of the total basic anions (hydroxyl groups) present in a solution. It also represents, particularly in water analysis, the bi-carbonate, carbonate, and occasionally, the borate, silicate, and phosphate salts which will react with water to produce the hydroxyl groups. ALLEN TYPE SCREW - A screw with a recessed hex shaped head. ALLOY - A substance having metal properties and being composed of two or more chemical elements of which at least one is a metal. ALLOY STEEL - Steel containing specific quantities of alloying elements (other than carbon) and commonly accepted amounts of manganese, copper, silicon, sulfur, and phosphorus). ALTERNATING CURRENT (AC) - Electric current in which the direction of the current alternates or reverses. In a 60 Hertz (cycle) current, the direction of current flow reverses in 1/120th of a second; most commonly used current. ALTERNATOR - A device which converts mechanical energy, into alternating current.

ALTIMETER - An instrument used to measure the height above a reference point, such as ground or sea level. ALUM - Is an aluminum sulfate or filter alum. Acts in the range of 5.0 to 8.0 pH. ALUMINA - Aluminum oxide occasionally found as an impurity in water in very small amounts. AMBIENT AIR TEMPERATURE - Temperature of fluid (usually air) which surrounds object on all sides. AMBIENT CONDITIONS - The conditions of temperature, pressure, and humidity, existing around an instrument. AMBIENT NOISE -The normal sound in a room or other location. AMERICAN STANDARD PIPE THREAD - A type of screw or thread, commonly used on pipe fittings to assure a tight seal. AMERICAN WIRE GAUGE (AWG) - A system used in the United States for measuring the size of solid wires. AMINE - A chemical use in water treatment as a filming or neutralizing agent to protect the metal parts. AMMETER - An instrument for measuring the magnitude of electric current flow. AMMETER SHUNT - A low-resistance conductor, placed in parallel (shunt) with an ammeter movement, so that most of the current flows through the shunt, and only a small portion flows through the ammeter. This extends the useful range of the meter. AMMONIA - Chemical combination of nitrogen and hydrogen (NH3). Ammonia is a very efficient refrigerant and identified as R-117. AMORPHOUS - A solid not having a repetitive three-dimensional pattern of atoms. AMPACITY - A wire's ability to carry current safely, without undue heating. The term formerly used to describe this characteristic was current capacity of the wire.

AMPERAGE - An electron or current flow of one coulomb per second, past a given point in a circuit. AMPERE - The unit used for measuring the quantity of an electrical current flow. One ampere represent a flow of one coulomb per second. AMPERE HOUR - A term used for rating battery capacity. As stated, an ampere for an hour; ex: 5 amperes for 20 hours = 100 amp hour on a 20 hr rating. AMPERE TURNS - A term used to measure magnetic force. It represents the product of amperes, times the number of turns of the coil, in an electromagnet. AMPLIFICATION - The process of obtaining an output signal greater than the input signal, through auxiliary power controlled by the input signal. The process of increasing the strength, current, power, or voltage, of the signal. AMPLITUDE - The maximum instantaneous value of alternating current or voltage. It can be in either a positive or negative direction. The greatest distance through which an oscillating body moves from the mid point. ANAEROBIC - A condition in which "free" or dissolved oxygen is not present in the water. ANALYSIS - The process of determining the composition of a substance, by chemical or physical methods. ANEMOMETER - An instrument for measuring the velocity of a fluid. ANGLE OF LAG OR LEAD - The phase angle difference, between two sinusoidal wave forms having the same frequency. ANGLE VALVE - A type of globe valve design, having pipe openings at right angles to each other. Usually one opening on the horizontal plane and one on the vertical plane. ANGSTROM UNITS - A unit of wave length, equal in length to one ten billionth. ANHYDROUS CALCIUM SULFATE - A dry chemical, made of calcium, sulfur, and oxygen.

ANION - A negatively charged ion such as the chloride ion (Cl-). ANION INTERCHANGE - The displacement of one negatively charged particle by another on an anion-exchange material. This principle is used with water treatment. ANNEAL - To soften by heating and allowing to cool slowly. ANNEALING - A process of heat treating metal, to get the desired properties of softness and ductility, (easy to form). ANODE - In electrolysis or electrochemical corrosion, a site where metal goes into solution as a cation leaving behind an equivalent of electrons to be transferred to the opposite electron, called the cathode. ANODIZING - The treatment of a metal surface whereby the metal is made anodic. ANSI - American National Standard Institute, which is an organization defining standards for computer language. ANSI-B.31.1 - Power Piping. ANSI-B.31.5 - Refrigeration Piping. ANTI KNOCK VALUE - A premature explosive combustion, as the detonation of the fuel air mixture in an internal combustion engine, produces a characteristic knock. The Anti Knock Value is the measure of its resistance to the condition which tends to produce this knock. ANTICIPATING CONTROL - One which, by artificial means, is activated sooner than it would be without such means, to produce a smaller differential of the controlled property. Heat and cool anticipators are commonly used in thermostats. ANTICIPATORS - A small heater element in two-position temperature controllers which deliberately cause false indications of temperature in the controller in an at tempt to minimize the override of the differential and smooth out the temperature variation in the controlled space. ANTI-CORROSIVE ADDITIVE - A lubricant additive to reduce corrosion.

ANTI-FOAM ADDITIVE (FOAM INHIBITOR) An additive used to reduce or prevent foaming. ANTIFOAM AGENTS - The reduction of carry over by the addition of polymerized esters, alcohol’s, and amides. The antifoam agent is absorbed on the steam generating surface resulting in a hydrophobic condition, causing fewer but larger steam bubbles, which readily coalesce. These agents also weaken the wall of the bubble formed, causing them to quickly burst on the water surface. ANTIFOULANTS - Are materials which prevent fouling from depositing on heat transfer equipment. Materials that prevent deposits forming; include anti- oxidants, metal coordinators, and corrosion inhibitors. Compounds that prevent deposition are surfactants. They act as detergents or dispersants. ANTIFREEZE - Compounds of glycol’s or alcohol’s, that lower the freezing point of cooling water systems. ANTIOXIDANT - A substance which when added in small amounts to petroleum products, will delay or inhibit undesirable changes; such as the formation of gum, sludge, and acidity, which are brought about by oxidation. ANTI-OXIDANT - An additive for the purpose of reducing the rate of oxidation and subsequent deterioration of the material. ANTI-SCUFFING LUBRICANT - A lubricant that is formulated to avoid scuffing. ANTI-SEIZURE PROPERTY - The ability of the bearing material to resist seizure during momentary lubrication failure. ANTI-WEAR ADDITIVE - A lubricant additive to reduce wear. API - American Petroleum Institute. API GRAVITY (API DEGREE) - A measure of density used in the US petroleum industry. APPARENT (EMF) - The apparent voltage, as measured by the drop in pressure due to a current flowing through a resistance.

APPARENT WATTS - The product of volts times amperes, in an alternating current circuit. AQUEOUS - Watery. A substance containing water. AQUIFER - A porous, subsurface geological structure carrying or holding water. ARC - A flash, caused by an electric current ionizing a gas or vapor. ARC BRAZING - A brazing process in which the heat required is obtained from an electric arc. ARC FURNACE - An electric furnace, in which heat is produced by an arc between two electrodes. ARC WELDING - A group of welding processes which produce coalescence of metals by heating them with an arc, with or without the application of pressure, and with or without the use of a filler metal. ARC WELDING - A process where coalescence is obtained by heating with an electric arc. ARCHIMEDES PRINCIPAL - States that an upward force acting on a body wholly or partly submerged in a fluid, is equal to the weight of the fluid displaced, and acts through the center of gravity of the fluid displaced, or the center of buoyancy. ARMATURE - the rotating part of an electric motor or generator. The moving part of a relay or vibrator. ARMATURE AIR GAP - The air space between the stationary and rotating parts of a motor or generator, through which magnetic lines of force pass. ARMATURE BACK AMPERE TURNS - The magnetic field produced by current flowing in the armature winding, that opposes and reduces the number of magnetic lines of force, produced by the field magnets of a motor or generator. ARMATURE BAR - Copper bars used in place of wire windings, in large armatures, generators, or motors.

ARMATURE CIRCUIT - The path that the current takes, in flowing through the windings from one brush to another. ARMATURE COIL - The loop or coil of copper wire, placed on the armature core, and forming part of the winding. ARMATURE CORE -The laminated iron part of the armature, formed from thin sheets or disks of steel, on which the windings are placed. ARMATURE CURRENT - The current flowing from the armature of a generator, to the armature of a motor. Not including the current taken by the shunt field. ARMATURE DEMAGNETIZATION - The reduction in the effective magnetic lines of force, produced by the armature current. ARMATURE REACTION - The effect, that the magnetic field produced by the current flowing in the armature, has on the magnetic field produced by the field coils. ARMATURE REGULATING RESISTORS - Are resistors, designed to regulate the speed or torque of a loaded motor, by placing a resistance in the armature or power circuit. ARMATURE RESISTANCE - The resistance of the wire used in the windings of the armature, measured between the rings or brushes, or from positive to negative terminals. ARMATURE SLOT -The groove or slot in the armature core, into which the coils or windings are placed. ARMATURE TESTER - Any device used for locating faults or defects in the armature winding. ARMATURE VARNISH - Is a liquid put on the field and armature windings, to improve the insulation of the cotton covering on the wires. ARMATURE WINDING - All of the copper wire placed on the armature, and through which the current flows. AROMATICS - A group of hydrocarbons of which benzene is the parent. They are called "aromatics" because many of their derivatives have sweet or aromatic odorous.

ARTIFICIAL MAGNET - Is a manufactured magnet, which is distinguished from a natural occurring magnet. ASHRAE - The American Society of Heating, Refrigeration, and Air Conditioning Engineers. ASME - American Society of Mechanical Engineers. ASME APPENDIX SECTION I - Explains matter which is mandatory, unless specifically referred to in the rules of the code, including formulas. ASME BOILER CODE - The boiler code listing standards, specified by the American Society of Mechanical Engineers, for the construction of boilers. ASME PART PEB SECTION I - Requirements for electric boilers. ASME PART PFH SECTION I - Requirements for feed water heaters. ASME PART PFT SECTION I - Requirements for firetube boilers. ASME PART PG SECTION I - General requirements for all methods of construction. ASME PART PMB SECTION I - Requirements for miniature boilers. ASME PART PVG SECTION I - Requirements for organic fluid vaporizer generators. ASME PART PW SECTION I - Requirements for boilers fabricated by welding. ASME PART PWT SECTION I - Requirements for watertube boilers. ASME SECTION I - Power Boilers. ASME SECTION II - Material specifications. ASME SECTION III - Nuclear Power Plant Components. ASME SECTION IV - Heating boilers ASME SECTION IX ASME SECTION V - Nondestructive examination.

ASME SECTION VI - Recommended rules for the care and operation of heating boilers. ASME SECTION VII - Recommended rules for the care and operation of power boilers. ASME SECTION VII APPENDIX - Consists of conversion factors for converting Imperial units to SI Units. ASME SECTION VII SUBSECTION C1 - Rules for routine operation of power boilers. ASME SECTION VII SUBSECTION C2 - Operating and maintaining boiler appliances. ASME SECTION VII SUBSECTION C3 - Rules for inspection. ASME SECTION VII SUBSECTION C4 - Prevention of direct causes of boiler failure. ASME SECTION VII SUBSECTION C5 - Is partial rules for the design of installations. ASME SECTION VII SUBSECTION C6 - Operation of boiler auxiliaries. ASME SECTION VII SUBSECTION C7 - Control of internal chemical conditions. ASME SECTION VIII - Pressure vessels. ASME SECTION X - Fiberglass reinforced plastic pressure vessels. ASME SECTION XI - Rules for in-service inspection of Nuclear Power Plant components. ASPECT RATIO - The ratio of the length to the width, of a rectangular air grille or duct. ASPIRATING PSYCHROMETER - A device which draws sample of air through it to measure humidity. ASPIRATION - Production of movement in a fluid by suction created by fluid velocity. ASTM - American Society for Testing and Materials.

ASYNCHRONOUS - Not having the same frequency. Out of step, or phase. ASYNCHRONOUS GENERATOR - An induction generator. ASYNCHRONOUS MOTOR - An induction motor, whose speed is not synchronous with the frequency of the supply line. ATMOSPHERE - Is the mixture of gases and water vapor surrounding the earth. ATMOSPHERIC ELECTRICITY - Is static electricity, produced between cloud fronts in the atmosphere. ATMOSPHERIC PRESSURE - Pressure exerted by the weight of the atmosphere; standard atmospheric pressure is 101.325 kPa or 1.01325 bars or 14.696 psia or 29.921 inches of mercury at sea level. ATOM - The smallest complete particle of an element, which can be obtained, yet which retains all physical and chemical properties of the element. ATOMIC NUMBER - The number of protons found in the nucleus of an atom, of an element. ATOMIC WEIGHT - The weight of an elementary atom, in relation to the weight of an atom of hydrogen. A hydrogen atom being taken as 1.00g. ATOMIZE - Process of changing a liquid to minute particles or a fine spray. ATTEMPERATING WATER IMPURITY - Refers to turbine deposits caused by impurities in the water used for attemperators. (Chemicals used with attemperating water should be of the volatile type). ATTEMPERATOR - An apparatus for reducing and controlling the temperature of a superheater vapor or a fluid. ATTENUATION - The sound reduction process in which sound energy is absorbed or diminished in intensity as the result of energy conversion from sound to motion or heat.

ATTRITION - The rubbing of one particle against another in a resin bed; frictional wear that will affect the site of resin particles. AUTOMATIC - Self-acting. Operating by its own mechanism, when activated by some triggering signal. AUTOMATIC CONTROL - The process of using the differences, between the actual value, and desired value, of any variable, to take corrective action, without human intervention. AUTOMATIC CONTROLLER - A device that measures the value of a measured variable, and operates to correct or limit the deviation from a selected reference. Both measuring and control applications. AUTOMATIC DEFROST - System of removing ice and frost from evaporators automatically. AUTOMATIC EXPANSION VALVE (AEV) - A type of metering device that senses low-side pressure and modulates in order to maintain low-side pressure constant. AUTOMATIC EXTRACTION UNIT TURBINE - Bleeds off part of the main steam flow at one, two, or three points. Valved partitions between selected stages control the extracted steam pressure at the desired level. When extracted steam flowing through the unit does not produce enough shaft power to meet the demand, more steam flows through the turbine to exhaust. Located between steam supply and process steam headers. AUTOMATIC FROST CONTROL - Control which automatically cycles refrigerating system to remove frost formation on evaporator. AUTOMATIC GOVERNING SYSTEM - A system which correlates steam flow, pressure, shaft speed, and shaft output, for any one turbine unit. AUTOMATIC ICE CUBE MAKER - Refrigerating mechanism designed to automatically produce ice cubes in quantity. AUTOMATIC RESET (INTEGRATION) - Is a type of control, in which the controller output, changes at a rate proportional to the deviation or error. The output will continue to change as long as any deviation or error exists. AUTOMATIC STARTER -

AUTOMATION - The employment of devices, which automatically control one or more functions. AUTOTRANSFORMER - A transformer in which both primary and secondary coils, have turns in common. The step up or step down of voltage, is accomplished by taps in common windings. AUXILIARY CONTACTS - A set of contacts that perform a secondary function, usually in relation to the operation of a set of primary contacts. Avogadro's HYPOTHESIS - States that equal volumes of different gases, at the same temperature and pressure, will contain equal numbers of molecules. Avogadro's AVERAGING ELEMENT - A thermostat sensing element which will respond to the average duct temperature. AXIAL FAN - Consists of a propeller or disc type of wheel within a cylinder that discharges air parallel to the axis of the wheel. AXIAL FLOW COMPRESSOR - Uses rotor blades shaped like airfoils, to bite into the air, speed it up, and push it into the subsequent stationary blade passages. These passages are shaped to form diffusers, that slow up the incoming air, and make it pressurize itself by catching up with the air ahead of it. AZEOTROPE - Having constant maximum and minimum boiling points. AZEOTROPIC MIXTURE - Example of azeotropic mixture - refrigerant R-502 is mixture consisting of 48.8 percent refrigerant R-22 and 51.2% R-115. The refrigerants do not combine chemically, yet azeotropic mixture provides refrigerant characteristics desired.

BACK PRESSURE - Pressure in low side of refrigerating system; also called suction pressure or low-side pressure. BACK PRESSURE TURBINE BACK SEATING - Fluid opening/closing such as a gauge opening or to seal the joint where the valve stem goes through the valve body. BACK WORK RATIO - Is the fraction of the gas turbine work used to drive the compressor. BACKGROUND NOISE - Sound other than the wanted signal. In room acoustics, the irreducible noise level measured in the absence of any building occupants. BACKING RING - Backing in a form of a ring, generally used in welding of piping. BACKWASH - The counter-current flow of water through a resin bed (that is, in at the bottom of the exchange unit, out at the top) to clean and regenerate the bed after exhaustion (water treatment). Also, the process whereby a filtering mechanism is cleaned by reversing the flow through the filter. BACTERIA - Microscopic unicellular living organisms. BAFFLE - Plate or vane used to direct or control movement of fluid or air within confined area. BAGHOUSE - A chamber containing bags for filtering solids out of gases. BALLAST GAS - Are the nonflammable portion of the gas, such as carbon dioxide. BAROMETER - Instrument for measuring atmospheric pressure. It may be calibrated in pounds per square inch, in inches of mercury in a column in millimeters or kPa. BASE - An alkaline substance. BASE METAL - The metal present in the largest proportion in an alloy. (Copper is the base metal in brass)

BASE METAL - The substrate metal that is coated or protected by a surface coating. BASICITY - The ability of a substance to boost the pH after neutralizing all the acid species. BATCH OPERATION - The utilization of ion-exchange resins to treat a solution in a container wherein the removal of ions is accomplished by agitation of the solution and subsequent decanting of the treated liquid. BAUDELOT COOLER - Heat exchanger in which water flows by gravity over the outside of the tubes or plates. BEARING, AIR - A bearing using air as a lubricant. BEARING, ALIGNING - A bearing with an external spherical seat surface that provides a compensation for shaft or housing deflection or misalignment. BEARING, ANNULAR - Usually a rolling bearing of short cylindrical form supporting a shaft carrying a radial load. BEARING, ANTI-FRICTION - A bearing containing a solid lubricant. BEARING, AXIAL LOAD (see bearing, thrust) BEARING, BABBITT - A bearing metal of non-ferrous material, containing several tin-based alloys, mainly copper, antimony, tin and lead. BEARING, BALL - A rolling element bearing in which the rolling elements are spherical. BEARING, BIG END - A bearing at the larger (crankshaft) end of a connecting rod in an engine. BEARING, BIMETAL - A bearing consisting of two layers. BEARING, BOTTOM END - (see bearing, big end) BEARING, BUSH - A plain bearing in which the lining is closely fitted into the housing in the form of a bush, usually surfaced with a bearing alloy.

BEARING, CIRCULAR STEP - A flat circular hydrostatic bearing with a central circular recess. BEARING, FIXED PAD - An axial or radial load bearing equipped with fixed pads, the surface of which a are contoured to promote hydrodynamic lubrication. BEARING, FLOATING - A bearing designed or mounted to permit axial displacement between shaft and housing. BEARING, FLOATING RING - A type of journal bearing that includes a thin ring between the journal and the bearing. The ring floats and rotates at a fraction of the journal rotational speed. BEARING, FLUID - (see hydrostatic bearing) BEARING, FULL JOURNAL - A journal bearing that surrounds the journal by a full 360°. BEARING, GAS - A journal or thrust bearing lubricated with gas. BEARING, HALF JOURNAL - A bearing extending 180° around a journal. BEARING, JOURNAL - A machine part in which a rotating shaft revolves or slides. BEARING, KINGSBURY TRUST - The predominant thrust bearing used in hydroelectric generators is the Kingsbury thrust bearing. It consist of a annular arrangement of babbit covered, pie shaped, stationary, shoes. The shoes form a circle around the rotating shaft. A cylindrical thrust block with a highly polished end is pressed onto the shaft and held to the shaft with half moon collars. The polished end of the shaft rests on the surfaces of the babbitted, stationary shoes. The shoes are mounted on spherical studs that allows them to tilt. As the hydraulic turbine spins the shaft, the collar turns on the shoes. BEARING, MAGNETIC - A type of bearing in which the force that separates the relatively moving surfaces is produced be a magnetic field. BEARING, MAIN - A bearing supporting the main power-transmitting shaft.

BEARING, MITCHELL -(see tilting pad bearing). BEARING, NEEDLE - A bearing in which the relatively moving parts are separated by long thin rollers that have a length-to-diameter ratio exceeding 5.0. BEARING, NONCONTACT - A bearing in which no solid contact occurs between relatively moving surfaces. BEARING, PEDESTAL - A bearing that is supported on a column or pedestal rather than on the main body of the machine. BEARING, PIVOT - An axial load bearing, radial-load-type bearing which supports the end of a shaft or pivot. BEARING, POROUS - Made from porous material, such as compressed metal powders, the pores acting either as reservoirs for holding or passages for supplied lubricant. BEARING, ROLLER - A bearing in which the relatively moving parts are separated by rollers. BEARING, RUBBING - A bearing in which the relatively moving parts slide without deliberate lubrication. BEARING, SELF-ALIGNING - A roller-element bearing with one spherical raceway that automatically provides compensation for shaft or housing deflection or misalignment. BEARING, SELF-LUBRICATING - A bearing independent of external lubrication. These bearings may be sealed for life after packing with grease or may contain self-lubricating material. BEARING, SLEEVE - A cylindrical plain bearing used to provide radial location for a shat, which moves axially. Sleeve bearings consist of one or more layers of bearing alloys, bonded to a steel backing. BEARING, SLIDE - A bearing used or positioning a slide or for axial alignment of a long rotating shaft. BEARING, STEP - A plane surface bearing that supports the lower end of a vertical shaft.

BEARING, THRUST - A bearing in which the load acts in the direction of the axis of rotation. BEARING, TILTING PAD - A pad bearing in which the pads are free to take up a position at an angle to the opposing surface according to the hydrodynamic pressure distribution over its surface. BEARING, TRUNNION - A bearing used as a pivot to swivel or turn an assembly. BED - A mass of ion-exchange resin particles contained in a column. BED DEPTH - The height of the resinous material in the column after the ion exchanger has been properly conditioned for effective operation. BED EXPANSION - The effect produced during backwashing when the resin particles become separated and rise in the column. The expansion of the bed due to the increase in the space between resin particles may be controlled by regulating backwash flow (typical with water treatment). BELLOWS - Corrugated cylindrical container which moves as pressures change, or provides a seal during movement of parts. BELLOWS SEAL - A type of mechanical seal that utilizes a bellows for providing secondary sealing. BENDING MOMENT - The algebraic sum of the couples or the moments of the external forces, or both, to the left or right of any section on a member subjected to bending by couples or transverse forces, or both. BERNOULLI'S THEOREM - In stream of liquid, the sum of elevation head, pressure head and velocity remains constant along any line of flow provided no work is done by or upon liquid in course of its flow, and decreases in proportion to energy lost in flow. BICACARBONATE ALKALINITY - The presence in a solution of hydroxyl (OH-) ions resulting from the hydrolysis of carbonates or bicarbonates. When these salts react with water, a strong base and a weak acid are produced, and the solution is alkaline. BICARBONATE - An ion or salt of carbonic acid, containing hydrogen, carbon, and oxygen (HC03), such as sodium bicarbonate, NaHC03.

BIMETAL STRIP - Temperature regulating or indicating device which works on principle that two dissimilar metals with unequal expansion rates, welded together, will bend as temperatures change. BIMETALLIC COUPLE - A joint or union of two dissimilar metals. BIMETALLIC ELEMENT BIOCIDE - A chemical used to control the population of troublesome microbes. BLACK LIQUOR - The liquid material remaining from pulpwood cooking in the soda or sulfate papermaking process. BLADE CLEARANCE (STEAM TURBINE) - Reaction turbine - the gap between blade and casing. Impulse turbine - the gap between the stationary and moving blades. BLAST FREEZER - Low-temperature evaporator which uses a fan to force air rapidly over the evaporator surface. BLAST FURNACE GAS - Is the waste product from furnaces used to smelt iron ores. BLEEDER VALVE - A valve designed to slowly relief a liquid or gas form system. BLEEDING - Slowly reducing the pressure of liquid or gas from a system or cylinder by slightly opening a valve. BLEEDOFF - The continuous removal of water from a re-circulating water system. BLEEDOFF RATE - The rate at which water is continuously removed from a system. BLOWDOWN - In connection with boilers or cooling towers, the process of discharging a significant portion of the aqueous solution in order to remove accumulated salts, deposits and other impurities. BOILER - Closed container in which a liquid may be heated and vaporized.

BOILER FEED WATER - The total water fed to a boiler producing steam. This water is the mixture of return steam condensate and makeup water. BOILER HORSEPOWER - The work required to evaporate 34.5 lb of water per hour into steam from and at 100°C. BOILER LAY-UP - Storing and protecting the boiler when not in use. BOILING - (See vaporization) BOILING OUT - The boiling of high alkaline water in boiler pressure parts for the removal of oil, greases, prior to normal operation or after major repairs. BOILING POINT - The temperature at which the vapor pressure of a liquid equals the absolute external pressure at the liquid-vapor interface. BOILING TEMPERATURE - Temperature at which a fluid changes from a liquid to a gas. BORE - Inside diameter of a cylinder. BOURDON TUBE - Thin-walled tube of elastic metal flattened and bent into circular shape, which tends to straighten as pressure inside is increased. Used in pressure gauges. BOYLES' LAW - If the temperature on a gas is constant, the volume is inversely proportional to the pressure. By formula - VP = V1P1 BRANCH CIRCUIT - Wiring between the last over current device and the branch circuit outlets. BRASS - A copper-zinc alloy containing up to 40% zinc and some smaller amounts of other metals. BRAYTON CYCLE (also referred to as the Joule Cycle) - A rotating machine in which compression and expansion take place. Gas turbine are such an example. BRAZE - A weld produced by heating an assembly to suitable temperatures and by using a filler metal having a liquid us above

450°C. The filler metal is distributed between the closely fitted facing surface of the joint by capillary action. BRAZING, BLOCK - A brazing process in which the heat required is obtained from heated blocks applied to the parts to be joined. BREAKTHROUGH - The first appearance in the solution flowing from an ion-exchange unit of unabsorbed ions similar to those which are depleting the activity of the resin bed. Breakthrough is an indication that regeneration of the resin is necessary. BRINE - Water saturated with a chemical such as salt. BRITISH THERMAL UNIT, (BTU) - The Btu is defined as the heat required to raise the temperature of a pound of water from 59° to 60°F. BRITTLENESS - The tendency of a material to fracture without first undergoing significant plastic deformation. BRONZE - A copper-rich copper tin alloy with or without small proportions of other elements. BTU - British Thermal Unit. Is the measure of heat energy. BUFFER - A substance used in solution, which accepts hydrogen ions or hydroxyl ions, added to the solution as acids or alkali’s, minimizing a change in pH. BULB - The name given to the temperature-sensing device located in the fluid for which control or indication is provided. The bulb may be liquid-filled, gas filled, or gas-and-liquid filled. Changes in temperature produce pressure changes within the bulb which are transmitted to the controller. BULGE - A local distortion or swelling outward caused by internal pressure on a tube wall or boiler shell due to overheating. BUS BAR - A heavy, rigid metallic conductor which carries a large current and makes a common connection between several circuits. Bus bars are usually uninsulated and located where the electrical service enters a building; that is, in the main distribution cabinet.

BYPASS - A pipe or duct, usually controlled by valve or damper, for conveying a fluid around an element of a system. BYPASS - Passage at one side of, or around, a regular passage. BYPASS FEEDER - A closed tank that is installed in a system in "bypass," that is, in a side stream taken off the system and leading back to the system rather than directly in-line.

Carnot Cycle - The most efficient heat engine cycle is the Carnot cycle, consisting of two isothermal processes and two adiabatic processes. The Carnot cycle can be thought of as the most efficient heat engine cycle allowed by physical laws CALCAREOUS COATING OR DEPOSIT - A layer consisting of a mixture of calcium carbonate and magnesium hydroxide deposited on surfaces being cathodically protected against corrosion, because of increased pH adjustment to the protected surface. CO - Carbon monoxide (CO) is a colorless, odorless, poisonous gas. It is produced by the incomplete burning of solid, liquid, and gaseous fuels. Appliances fueled with natural gas, liquefied petroleum (LP gas), oil, kerosene, coal, or wood may produce CO. Burning charcoal produces CO. Running cars produce CO CO2 - is an atmospheric gas composed of one carbon and two oxygen atoms. Carbon dioxide results from the combustion of organic matter if sufficient amounts of oxygen are present. It is also produced by various microorganisms in fermentation and is breathed out by animals. Plants absorb carbon dioxide during photosynthesis, using both the carbon and the oxygen to construct carbohydrates. It is present in the Earth's atmosphere at a low concentration and acts as a greenhouse gas. It is a major component of the carbon cycle. CALCIUM - A scale forming element found in boiler feedwater. CALCIUM CHLORIDE - A substance used to obtain calcium chloride brine. CALCIUM SULFATE - Chemical compound (CaSO4) which is used at a drying agent or desiccant in liquid line dryers. CALIBRATION - A process of dividing and numbering the scale of an instrument; also of correcting or determining the error of an existing scale, or of evaluating one quantity in terms of readings of another. CALORIE - It is equal to the amount of heat required to raise the temperature of one gram of water one degree Celsius. CALORIMETER - Device used to measure quantities of heat or determine specific heats.

CHANGE OF STATE - Change from one phase, such as solid, liquid or gas, to another. CAPACITANCE - The property of an electric current that permits the storage of electrical energy in an electrostatic field and the release of that energy at a later time. CAPACITOR, (CONDENSER) - A device that can store an electric charge when voltage is applied. CAPACITY - The adsorption activity possessed in varying degrees by ion-exchange materials. This quality may be expressed as kilograms per cubic foot, gram-milliequivalents per gram, pound-equivalents per pound, gram-milliequivalents per milliliter, and so on, where the numerators of these ratios represent the weight of the ions adsorbed and the denominators represent the weight or volume of the adsorbent. CAPILLARY - The name given to the thin tube attached to the bulb which transmits the bulb pressure changes to the controller or indicator. The cross sectional area of the capillary is extremely small compared to the cross section of the bulb so that the capillary, which is usually outside of the controlled fluid, will introduce the smallest possible error in the signal being transmitted from the bulb. CAPILLARY TUBE - The capillary tube is a metering device made from a thin tube approximately 0.5 to 6 meter long and from 0.025 to 0.090 inches in diameter which feeds liquid directly to the evaporator. Usually limited to systems of 1 ton or less, it performs all of the functions of the thermal expansion valve when properly sized. CARBON DIOXIDE - Compound of carbon and oxygen (CO2) which is sometimes used as a refrigerant. Refrigerant number is R-744. CARBON FILTER - Air filter using activated carbon as air cleansing agent. CARBON RINGS - To minimize steam leakage, gland sealing arrangement features an angle-type, carbon ring design with a packing case that is an integral part of the turbine case. Inconel springs hold the rings in place.

CARBON TETRACHLORIDE - Colorless nonflammable and very toxic liquid used as a solvent. It should never be allowed to touch skin and fumes must not be inhaled. CARBONACEOUS EXCHANGER - Ion-exchange materials of limited capacity prepared by the sulfonation of coal, lignite, peat, and so on. CARBONATE - An ion or salt of carbonic acid, containing carbon and oxygen such as calcium carbonate. (CaC03) CARBONATE HARDNESS - That hardness caused in water by bicarbonates and carbonates of calcium, and magnesium. CARBONATE-POLYMER TREATMENT - A treatment method using synthetic polymers, generally used with high hardness (60-70) ppm and high alkalinity. CARBOXYLIC - A term describing a specific acidic group (COOH) that contributes cat ion-exchange ability to some resins. CARRYOVER - The moisture and entrained solids forming the film of steam bubbles, as a result of foaming in a boiler. This condition is caused by a faulty boiler water condition. See also foaming. CASCADE - A series of stages in which the output of one stage is the input of the next stage. CASCADE SYSTEMS - Arrangement in which two or more refrigerating systems are used in series; uses evaporator of one machine to cool condenser of other machine. Produces ultra-low temperatures. CATHODE - In electrolysis or electrochemical corrosion, a site on a surface where actions in solution are neutralized by electrons to become elements that either plate out on the surface or react with water to produce a secondary reaction. CATHODE PROTECTION - A method of preventing corrosion by making the metal a cathode in a conducting medium by means of a direct electrical current that is galvanic. CATHODIC PROTECTION - Reduction of corrosion rate by shifting the corrosion potential of the electrode towards less oxidizing potential by applying an external electromotive force.

CATION - A positively charged ion that migrates through the electrolyte toward the cathode under the influence of a potential gradient. CATION-EXCHANGE SOFTENERS - Ion exchange units are known primarily as water softeners. But they can also remove nitrates, sulfates, and various toxic metals from water. ion exchangers. PDF CATIONIC - The condition of a polymer, colloid, or large particle having exchangeable anions on its surface and an opposite, positive charge on the substrata. CAUSTIC CRACKING - A form of stress-corrosion cracking most frequently encountered in carbon steels or iron-chromium-nickel alloys that are exposed to concentrated hydroxide solutions at temperature of 200 to 250°C. CAUSTIC EMBRITTLEMENT - An obsolete term replaced by caustic cracking. CAUSTIC SODA - A common water treatment chemical, sodium hydroxide. CAVITATION - The formation and collapse, within a liquid, of cavities or bubbles that contain vapor or gas or both. In general, cavitation originates from decreases in static pressure in the liquid. In order to erode a solid surface by cavitation, it is necessary for the cavitation bubbles to collapse on or close to that surface. CAVITATION EROSION - Progressive loss of original material from a solid surface due to continuing exposure to cavitation. CELSIUS TEMPERATURE SCALE - A thermometric scale in which the freezing point of water is called 0°C and its boiling point 100°C at normal atmospheric pressure. CENTANE NUMBER - A measure of ignition quality of a fuel or petroleum with reference to normal centane high-ignition quality fuel with an arbitrary number of 100. CENTRIFUGAL COMPRESSOR - Pump which compresses gaseous fluids by centrifugal force.

CENTRIFUGAL FORCE - is actually not a force but the experience of an inertial force experienced in a rotating reference frame acting away from the center of the rotation. It is equal in magnitude but opposite to the centripetal force required to constrain the body to move in a circular motion. Actually not a force but the experience of an inertial. CENTRIFUGAL FORCE -On a centrifugal pump, it is that force which throws water from a spinning impeller. CENTRIFUGAL PUMP - A pump consisting of an impeller fixed on a rotating shaft and enclosed in a casing, having an inlet and a discharge connection. The rotating impeller creates pressure in the liquid by the velocity derived from centrifugal force. CENTRIFUGAL PUMP - Pump which produces fluid velocity and converts it to pressure head. Centripetal force - is the force that causes an object to move in a circle, acting towards the centre of the circle. In the case of a satellite the centripetal force is gravity, in the case of an object at the end of a rope, the centripetal force is the tension of the rope. CHANGE OF STATE - Condition in which a substance changes from a solid to a liquid or a liquid to a gas caused by the addition of heat. Or the reverse, in which a substance changes from a gas to a liquid, or a liquid to a solid, caused by the removal of heat. CHANNELING - Cleavage and furrowing of the bed due to faulty operational procedure, in which the solution being treated follows the path of least resistance, runs through these furrows, and fails to contact active groups in other parts of the bed, (water treatment). CHARGE - Amount of refrigerant placed in a refrigerating unit. CHARGING BOARD - Specially designed panel or cabinet fitted with gauges, valves and refrigerant cylinders used for charging refrigerant and oil into refrigerating mechanisms. CHECK VALVE - Device which permits fluid flow in one direction. CHELATE - Is a molecule, similar to an ion exchanger, capable to withdraw ions from their water solutions into soluble complexes.

CHEMICAL CLEANING - Using a solvent solution to remove mill scale and corrosion products. CHEMICAL FEEDLINE - The line which feeds the boiler treatment chemicals into the boiler. CHEMICAL PRECIPITATION - When the chemicals react with the dissolved minerals in the water to produce a relative insoluble reaction product. A typical example of this takes place with the lime-soda softening process. CHEMICAL REFRIGERATION - System of cooling using a disposable refrigerant. Also called an expendable refrigerant system. CHEMICAL STABILITY - Resistance to chemical change which ionexchange resins must possess despite contact with aggressive solutions. CHILL FACTOR - Calculated number based on temperature and wind velocity. CHILLED-WATER SYSTEM - A re-circulating water system using water chilled in a refrigeration machine as a source for cooling. CHILLER/HEATERS - A unit that supplies either chilled water for cooling or hot water for heating, (HVAC). CHLORIDE - An ion, compound, or salt of chlorine, such as sodium chloride (NaCl) or calcium chloride (CaCl2). CHLORINATION - A process in which chlorine gas or other chlorine compounds are added to the water for the purpose of disinfecting. CHOKE TUBE - Throttling device used to maintain correct pressure difference between high-side and low-side in refrigerating mechanism. Capillary tubes are sometimes called choke tubes. CHORDAL THERMOCOUPLE - A thermocouple installed in furnace tubes, designed to measure the effectiveness of water treatment within the boiler. CIRCUIT - An electrical arrangement requiring a source of voltage, a closed loop of wiring, an electric load and some means for opening and closing it.

CIRCUIT BREAKER - A switch-type mechanism that opens automatically when it senses an overload (excess current). CLAY - Finely suspended earth mineral sometimes found as an impurity in water. CLEARANCE SPACE - Space between top of piston and the valve plate. CLEARANCE VAPOR - The vapor remaining in the clearance space at the end of each discharge stroke. CLOSED CYCLE - is the gas turbine arrangement, in which the exhaust is directed back again to compressor without coming in contact with the atmospheric air. CLOSED FEED WATER HEATER - An indirect-contact feed water heater. Steam and water are separated by tubes. CLOSED RE-CIRCULATING WATER SYSTEM - A system using as a heattransfer medium water that continuously circulates through closed piping and heat exchanger without evaporation. CO COAGULANT - A substance that promotes the clumping of particulate matter in water, forming a larger mass and thus promoting settling of particulates and clarification of the water. COAGULATION - Is the process whereby finely divided particles of turbidity and color, capable of remaining in suspension indefinitely, are combined by chemical means into masses sufficiently large to effect rapid settling. COALESCENCE - The gathering together of coagulated colloidal liquids into a single continuous phase. CODE INSTALLATION - Refrigeration or air conditioning installation which conforms to the local code and/or the national code for safe and efficient installations. CO-EFFICIENT OF CONDUCTIVITY - Measure of the relative rate at which different materials conduct heat. Copper is a good conductor of heat and, therefore, has a high coefficient of conductivity.

COEFFICIENT OF EXPANSION - A measure of the change in length or volume of an oject, specifically, a change measured by the increase in length or volume of an object per unit length or volume. COEFFICIENT OF FRICTION - The dimensionless ratio of the friction force (F) between two bodies to the normal force (N) pressing these bodies together - m (f) = (F/N) COEFFICIENT OF PERFORMANCE (COP) - Ratio of work performed or accomplished as compared to the energy used under designated operating conditions. COEFFICIENT OF THERMAL EXPANSION - The fractional change in length (or sometimes in volume, when specified) of a material for a unit change in temperature. COGENERATION - A term used to describe the combination of different thermodynamic cycles for the purpose of increasing all-over cycle efficiency. CO-GENERATION GENERATION - a term applied to identify the generation of people interested in co-generation. COLD - The absence of heat; a temperature considerably below normal. COLD DECK -The cooling section of a mixed air zoning system. COLD JUNCTION - That part of a thermoelectric system which absorbs heat as the system operates. COLD PROCESS - A water treatment process carried out at room temperature. COLD WALL - Refrigerator construction which has the inner lining of refrigerator serving as the cooling surface. COLLOIDAL - A state of suspension in a liquid medium in which extremely small particles are suspended and dispersed but not dissolved. COLLOIDS - Organic matter of very fine particle size, usually in the range of 10-5 to 10-7 cm in diameter. It tends to inhibit the formation

of dense scale and results in the deposition of sludge, or causes it to remain in suspension, so that it may be blown from the boiler. COLUMN OPERATION - Conventional utilization of ion-exchange resins in columns through which pass, either upflow or down flow, the solution to be treated. COMBINED FEEDER CUTOFF - A device that regulates makeup water to a boiler in combination with a low-water fuel cutoff. COMBINED STEAM-GAS PLANT - where a gas turbine is combined with steam plant in order to utilize the waste heat. COMBINED TREATMENT - A method of physical treatment , followed by the addition of chemicals to remove oxygen. COMBUSTION - The act or process of burning. COMFORT CHART - A chart showing effective temperatures with drybulb temperatures and humidity's (and sometimes air motion) by which the effects of various air conditions on human comfort may be compared. COMFORT COOLER - System used to reduce the temperature in the living space in homes. These systems are not complete air conditioners as they do not provide complete control of heating, humidifying, dehumidification, and air circulation. COMFORT COOLING - Refrigeration for comfort as opposed to refrigeration for storage or manufacture. COMFORT ZONE - (Average) the range of effective temperatures over which the majority (50 percent or more) of adults feels comfortable; (extreme) the range of effective temperatures over which one or more adults feel comfortable. An area on the psychometric chart which shows conditions of temperature, humidity and sometimes air movement in which most people are comfortable. COMMON NEUTRAL - A neutral conductor that is common to, or serves, more than one circuit. COMPOSITION - The elements or chemical components that make up a material and their relative proportions.

COMPOUND - They are chemically combined elements with definite proportions of the component elements. COMPOUND GAUGE - Instrument for measuring pressures both above and below atmospheric pressure. COMPOUND REFRIGERATING SYSTEMS - System which has several compressors or compressor cylinders in series. The system is used to pump low pressure vapors to condensing pressures. COMPRESSION - Term used to denote increase of pressure on a fluid by using mechanical energy. COMPRESSION RATIO - Ratio of the volume of the clearance space to the total volume of the cylinder. In refrigeration it is also used as the ratio of the absolute low-side pressure to the absolute high-side pressure. COMPRESSION, ADIABATIC - Is compressing a gas without removing or adding heat. COMPRESSOR - Pump of a refrigerating mechanism which draws a low pressure on cooling side of refrigerant cycle and squeezes or compresses the gas into the high-pressure or condensing side of the cycle. COMPRESSOR - The pump which provides the pressure differential to cause fluid to flow and in the pumping process increases pressure of the refrigerant to the high side condition. The compressor is the separation between low side and high side. COMPRESSOR DISPLACEMENT - Volume, in cubic inches, represented by the area of the compressor piston head or heads multiplied by the length of the stroke. COMPRESSOR SEAL - Leak proof seal between crankshaft and compressor body in open type compressors. COMPRESSOR SURGING - An instability of air flow with axial compressor on the first stages of these compressors. Air flow might even be reversed that point. COMPRESSOR TURBINE - in terms of a gas turbine arrangement, it is the turbine which drives the compressor only.

COMPRESSOR, CLEARANCE POCKET - Small space in a cylinder from which compressed gas is not completely expelled. This space is called the compressor clearance space or pocket. For effective operation, compressors are designed to have as small a clearance space as possible. COMPRESSOR, ROTARY BLADE - Mechanism for pumping fluid by revolving blades inside cylindrical housing. COMPRESSOR, SINGLE-STAGE - Compressor having only one compressive step between low-side pressure and high-side pressure. COMPRESSIBILITY - The ease which a fluid may be reduced in volume by the application of pressure, depends upon the state of the fluid as well as the type of fluid itself. CONDENSATE - The liquid formed by condensation of a vapor. In steam heating, water condensed from steam; in air conditioning, water extracted from air, as by condensation on the cooling coil of a refrigeration machine. CONDENSATE POLISHER - A device used to clean the returning condensate to the boiler feedwater system. CONDENSATE PUMP - Device to remove water condensate that collects beneath an evaporator. CONDENSATION - Process of changing a vapor into liquid by extracting heat. Condensation of steam or water vapor is effected in either steam condensers or dehumidifying coils, and the resulting water is called condensate. CONDENSE - Action of changing a gas or vapor to a liquid. CONDENSER - An apparatus used to transfer heat from a hot gas, simultaneously reducing that gas to a liquid. CONDENSER TUBE - The heat transfer surface in a condenser. CONDENSER-WATER SYSTEM - A re-circulating cooling water used as a heat transfer fluid for the condensation of a gas. CONDENSING BLEEDER TURBINE -

CONDENSING TEMPERATURE - The temperature at which the condensing gas is returned to a liquid at the same pressure. CONDENSING TURBINE - With this turbine, the steam exhausts to the condenser and the latent heat of the steam is transferred to the cooling water. The condensed steam is returned to the boiler as feedwater. CONDENSING UNIT - Part of a refrigerating mechanism which pumps vaporized refrigerant from the evaporator, compresses it, liquefies it in the condenser and returns it to the refrigerant control. CONDENSING UNIT SERVICE VALVES - Shutoff valves mounted on condensing unit to enable service technicians to install and/or service unit. CONDENSING UNIT, REFRIGERANT - An assembly of refrigerating components designed to compress and liquefy a specific refrigerant, consisting of one or more refrigerant compressors, refrigerant condensers, liquid receivers (when required) and regularly furnished accessories. CONDUCTANCE, ELECTRICAL - The reciprocal (opposite) of resistance and is the current carrying ability of any wire or electrical component. Resistance is the ability to oppose the flow of current. CONDUCTANCE, SURFACE FILM - Time rate of heat flow per unit area under steady conditions between a surface and a fluid for unit temperature difference between the surface and fluid. CONDUCTION - Transfer of heat by direct contact. CONDUCTIVITY (ELECTRICAL) - The ability of a liquid to conduct an electrical current and indicating the presence of cat ions and anions. Conductivity is usually expressed in Micromos per cm. CONDUCTIVITY (THERMAL) - The time rate of heat flow through unit thickness of an infinite slab of homogeneous material in a direction perpendicular to the surface, induced by unit temperature difference. (W/m · K) CONDUCTIVITY METER - An electric instrument used to measure the conductivity of water to determine its content of dissolved solids.

CONDUCTIVITY, THERMAL - The time rate of heat flow through unit area and unit thickness of a homogeneous material under steady conditions when a unit temperature gradient is maintained in the direction perpendicular to area. Materials are considered homogeneous when the value of the thermal conductivity is not affected by variation in thickness or in size CONDUCTOR - Substance or body capable of transmitting electricity or heat. CONDUIT - A round cross-section electrical raceway, of metal or plastic. CONGEALER - Also known as freezer. CONGRUENT PHOSPHATE CONTROL - Similar as a coordinated phosphate control but more restrictive where the equilibrium is based on maintaining a ratio of 2.6 Na/1.0 PO4, instead of 3.0/1.0 PO4. CONNECTED LOAD - The sum of all loads on a circuit. (1) Connection in Parallel: System whereby flow is divided among two or more channels from a common starting point or header. (2) Connection in Series: System whereby flow through two or more channels is in a single path entering each succeeding channel only after leaving the first or previous channel. CONSTRICTOR - Tube or orifice used to restrict flow of a gas or a liquid. CONTAMINATION - The introduction into water of microorganisms, chemicals, toxic materials, waste water in a concentration that makes the water unfit for its next intended use. CONTROL - A device for regulation of a system or component in normal operation, manual or automatic. If automatic, the implication is that it is responsive to changes of pressure, temperature or other property whose magnitude is to be regulated. CONTROL POINT - The value of the controlled variable which the controller operates to maintain. CONTROL VALVE - Valve which regulates the flow or pressure of a medium which affects a controlled process. Control valves are operated by remote signals from independent devices using any of a

number of control media such as pneumatic, electric or electro hydraulic. CONTROLLED DEVICE - One which receives the converted signal from the transmission system and translates it into the appropriate action in the environmental system. For example: a valve opens or closes to regulate fluid flow in the system. CONTROLLER - A device capable of measuring and regulating by receiving a signal from a sensing device, comparing this data with a desired value and issuing signals for corrective action. CONVECTION - The movement of a mass of fluid (liquid or gas) caused by differences in density in different parts of the fluid; the differences in density are caused by differences in temperature. As the fluid moves, it carries with it its contained heat energy, which is then transferred from one part of the fluid to another and from the fluid to the surroundings. CONVECTION, FORCED - Convection resulting from forced circulation of a fluid, as by a fan, jet or pump. CONVECTION, NATURAL - Circulation of gas or liquid (usually air or water) due to differences in density resulting from temperature changes. CONVERGENT NOZZLE - Impulse Turbine - Stationary convergent nozzles are used for smaller pressure drops where the minimum exit pressure is 0.577 x the inlet pressure (the critical pressure for nozzles.) If the exit pressure is less than 0.577 x inlet pressure, eddycurrents are developed and the exit velocity will be less than calculated. CONVERGENT-DIVERGENT NOZZLE - Impulse Turbine - Stationary convergent-divergent nozzles prevent eddy-currents and the calculated velocity will be obtained even at large pressure drops. COOLER - Heat exchanger which removes heat from a substance. COOLING EFFECT, SENSIBLE - The difference between the total cooling effect and the dehumidifying effect, usually in watts.

COOLING EFFECT, TOTAL - Difference between the total enthalpy of the dry air and water vapor mixture entering the cooler per hour and the total enthalpy of the dry air and water vapor mixture leavir~ the cooler per hour, expressed in watts. COOLING TOWER - Device for lowering the temperature of water by evaporative cooling, in which water is showered through a space through which outside air circulates. A portion of the water evaporates, its latent heat of vaporization cooling that portion of the water which does not evaporate. COOLING, EVAPORATIVE - Involves the adiabatic exchange of heat between air and water spray or wetted surface. The water assumes the wet-bulb temperature of the air, which remains constant during its traverse of the exchanger. COOLING, REGENERATIVE - Process of utilizing heat which must be rejected or absorbed in one part of the cycle to function usefully in another part of the cycle by heat transfer. COORDINATED PHOSPHATE CONTROL A treatment to prevent caustic gauging. Free caustic is eliminated by maintaining an equilibrium between the sodium and phosphate. Control is based on maintaining a ratio of 3.0 Na to/1.0 PO4. CORRATOR - A device or probe employed to measure current flow in a process flow. It consists of two identical electrodes, to which a small current is applied and measured, from which corrosion rates can be calculated. CORROSION - The chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties. CORROSION, ANODE - The dissolution of an metal acting as an anode. CORROSION, ATMOSPHERIC - The gradual degradation or alteration of a material by contact with substances present in the atmosphere, such as oxygen, carbon dioxide, water vapor, and sulfur and chlorine compounds. CORROSION, BIOLOGICAL - Deterioration of metals as a result of the metabolic action of microorganisms. Also often named fouling.

CORROSION, CATHODIC - Corrosion resulting resulting from a cathodic condition of a structure usually caused by the reaction of an amphoteric metal with the alkaline products of electrolysis. CORROSION, CAVITATION - A process involving conjoint corrosion and cavitation. CORROSION, CONCENTRATION ATTACK - A form of corrosion caused by the concentration of caustic or phosphate salts under porous deposits, generally iron oxide. Sometimes found at welded tubes and due to steam blanketing. CORROSION, CONCENTRATION-CELL - Pitting type of corrosion caused by an electrical potential differential between surfaces of a metal as a result of deposits or differences in the solution concentration in contact with the metal. CORROSION, COUPONS - Pre-weighed metal strips installed into fluid systems for the purpose of monitoring metal losses. CORROSION, CREVICE - Localized corrosion of a metal surface at, or immediately adjacent to an area that is shielded from full exposure to the environment because of close proximity between metal and the surface of another metal. CORROSION, DEACTIVASION - The process of prior removal of the active corrosive constituents, usually oxygen, from a corrosive liquid by controlled corrosion of expendable metal or by other chemical means, therby making the liquids less corrosive. CORROSION, DEPOSIT (also called poultice corrosion) - Corrosion occuring under or around a discontinous deposit on a metallic surface. CORROSION, EFFECT - A change in any part of the corrosion system caused by corrosion. CORROSION, ELECTROCHEMICAL - Corrosion that is accompanied by a low of electrons between cathodic and anodic areas on metallic surfaces. CORROSION, EMBRITTLEMENT - The severe loss of ductility of a metal resulting from corrosive attack, usually intergranular and often not visible.

CORROSION, EXTERNAL - A chemical deterioration of the metal on the fireside of boiler heating surfaces. CORROSION, FATIGUE - The process in which a metal fractures prematurely under conditions of simultaneous corrosion and repeated cyclic loading at lower stress levels or fewer cycles than would be required in the absence of the corrosive environment. CORROSION, FILIFORM - Corrosion that occurs under organic coatings on metals as fine wavy hairlines. CORROSION, FRETTING - A type of corrosion which occurs where metals slide over each other. Long tubes in heat exchangers often vibrate, causing metal to metal contact, tube supports etc.. The metal to metal rubbing causes mechanical damage to the protective oxide coating. CORROSION, GALVANIC - Corrosion of a metal caused by its contact with a metal of lower activity; this contact results in an electron flow or current and dissolution of one of the metals. CORROSION, GASEOUS - Corrosion with gas as the only corrosive agent and without any aqueous phase on the surface of the metal. Also called dry corrosion. CORROSION, GENERAL - A form of deterioration that is distributed more or less uniformly over a surface. CORROSION, GRAPHITIC - Corrosion of grey iron in which the iron matrix is selectively leached away, leaving a porous mass of graphite behind. This type of corrosion occurs in relativel mild aquous solutions and on buried piping. CORROSION, HOT - An accelerated corrosion of metal surfaces that results from the combined effect of oxidation and ractions with sulfur compounds or other contminants such as chlorides, to form a molten salt on a metal surface that fluxes, destroys or disrupts the normal protective oxide. (commonly found in pulp mills) CORROSION, IMPINGEMENT - A form of erosion-corrosion generally associated with local impingement of a high velocity, flowing fluid against a solid surface.

CORROSION, INFLUENCED - The corrosion cause by organisms due to their discharge containing sulfur compounds and the depolarization with other types of discharge due to the presence of the microorganisms. CORROSION, INHIBITORS - Substances that slow the rate of corrosion. CORROSION, INTERCRYSTALINE -(see intergranular cracking) CORROSION, INTERGRANULAR - Localized attack occurring on the metal grain boundaries. This is commonly found with stainless steels which have been improperly heat treated. CORROSION, INTERNAL - Usually refers to the internal corrosion and is considered an electrochemical deterioration of the boiler surface at or below the water surface. CORROSION, LOCALIZED - Corrosion at discrete sites, for example, crevice corrosion, pitting, and stress-corrosion cracking. CORROSION, LOCALIZED - Non-uniform corrosion of a metal surface highlighted by spotty or pitting-type corrosion. CORROSION, MICROBIAL - (see biological corrosion). CORROSION, OXYGEN DEFICIENCY - A form of crevice corrosion in which galvanic corrosion proceeds because oxygen is prevented from diffusing into the crevice. CORROSION, POTENTIAL - The voltage between a corroding metal and a reference electrode. CORROSION, POULTICE - (see corrosion, deposit) CORROSION, POULTICE - A term used in the automotive industry to describe the corrosion of vehicle body parts due to the collection of road salts and debries on ledges and in pockets that are kept moist by weather and washing. CORROSION, PROTECTION - Modification of a corrosion system so that corrosion damage is mitigated.

CORROSION, RESISTANCE - The ability of a material to resist deterioration by chemical or electrochemical reaction with its environment. CORROSION, STRAY CURRENT - A form of attack caused by electrical currents going through unintentional path. CORROSION, STRESS - Preferential attack of areas under stress in a corrosive environment, where such a environment alone would not have caused corrosion. CORROSION, STRESS CORROSION CRACKING - Material deterioration due to cracking, by being under static stress either applied or residual. CORROSION, SWEET - The deterioration of metal caused by contact with carbon dioxide in water. CORROSION, THERMO-GALVANIC - Corrosion resulting from an electrochemical cell caused by a thermal gradient. CORROSION, UNIFORM - The simplest form of corrosion. It attacks all surfaces exposed to a corrodent. CORROSIVE WEAR - A material deterioration due to the co-joint action of corrosion and mechanical action. CORROSIVITY - An indication of the corrosiveness of the water of material. The corrosivity of a water as described by the water’s pH, alkalinity, hardness, temperature, total dissolved solids, dissolved oxygen concentration and the Langerier Index. COUNTER-FLOW HEAT EXCHANGER - When the fluid to be cooled flows against the direction of the coolant. In heat exchange between two fluids, opposite direction of flow, coldest portion of one meeting coldest portion of the other. COVALENT BOND - A bond in which two atoms share pair of electrons. CRANKSHAFT SEAL - Leak proof joint between crankshaft and compressor body. CRAZE CRACKING (OR CHECKING) - Irregular surface cracking of metal associated with thermal cycling.

CREEP - Time dependent permanent strain under stress. This is used to rate the resistance of a material to plastic deformation under sustained load. CREEP STRENGTH - The constant nominal stress that will cause a specified quantity of creep in a given time at constant temperature. Creep strength is expressed as the stress necessary to produce 0.1% strain in 1000 hours. CREEP, DYNAMIC - Creep that occurs under conditions of fluctuating load or fluctuating temperatures. CRISPER - Drawer or compartment in refrigerator designed to provide high humidity along with low temperature to keep vegetables, especially leafy vegetables - cold and crisp. CRITICAL HUMIDITY - The relative humidity above which the atmospheric corrosion rate of some metals increase sharply. CRITICAL POINT - A point at which the saturated liquid and saturated vapor states are identical. Also, the latent heat of evaporization is zero at this point. CRITICAL PRESSURE - The pressure at the critical temperature above which the fluid no longer has the properties of a liquid, regardless of further increase of pressure. CRITICAL TEMPERATURE - That temperature above which the vapor phase cannot be condensed to liquid by an increase in pressure. CRITICAL VELOCITY - Maximum velocity is obtained and no further pressure drop is obtained. (Acoustic Velocity). CROSS COMPOUND TURBINE - These turbines are large turbines with parallel shafts with a generator on each shaft. The steam flows through the high pressure turbine, then is crossed-over to the low pressure turbine CRT - Cathode ray tube terminal. CRYOGENIC FLUID - Substance which exists as a liquid or gas at ultralow temperatures - 157°C.

CRYOGENIC SUPERCONDUCTOR SYSTEM - Uses helium to cool conductors to within few degrees of absolute zero where they offer no electric resistance. CRYOGENICS - Refrigeration which deals with producing temperatures of -157°C below zero and lower. Crystal Formation, Zone of Maximum: Temperature range in freezing in which most freezing takes place, i.e., about 25¡F to 30¡F for water. CRYSTALLITES - Atoms arranged in a repeating and definite structure. CRYSTALLIZATION - The separation, usually from a liquid phase on cooling, of a solid crystalline phase. CURRENT (I) - The electric flow in an electric circuit, which is expressed in amperes (amps). CURRENT DENSITY - The current flowing to or from a unit area of an electrode surface. CURTIS METHOD or Curtis stage - Velocity Compounding - This turbine design consists of one set of nozzles in which the steam is expanded from initial to exhaust pressure. The velocity of the steam resulting from this expansion is absorbed in two or more rows of moving blades. Rows of fixed or guide blades, attached to the casing, are set between rows of moving blades and receive and redirect the steam to the next row of moving blades. As the velocity is absorbed in more than one row of moving blades, the blade speed is less than if the velocity was all absorbed in one row of blades. CYCLE - A series of thermodynamic processes during which the working fluid can be made to undergo changes involving energy transition and is subsequently returned to its original state. CYCLE, REVERSIBLE - Theoretical thermodynamic cycle, composed of a series of reversible processes, which can be completely reversed. CYCLE, WATER TREATMENT - A complete course of ion-exchange operation. For instance, a complete cycle of cation exchange would involve regeneration of the resin with acid, rinse to remove excess acid, exhaustion, backwash, and finally regeneration.

CYCLES - A system that undergoes a series of processes and always returns to its initial state. CYCLES OF CONCENTRATION - The number of times the soluble mineral salts in a water supply have been concentrated in, a system. CYLINDER HEAD - Plate or cap which encloses compression end of compressor cylinder.

DALTON'S LAW OF PARTIAL PRESSURE - Each constituent of a mixture of gases behaves thermodynamically as if it alone occupied the space. The sum of the individual pressures of the constituents equals the total pressure of the mixture. DAMPER - A device used to vary the volume of air passing through an air outlet, air inlet or duct. DASHPOT - A damping device, usually consisting of a cylinder and a piston in which relative motion of either displaces a fluid such as air or oil, resulting in friction. DEADBAND - In HVAC, a temperature range in which neither heating nor cooling is turned on; in load management, a kilowatt range in which loads are neither shed nor restored. DE-AERATING HEATERS - Mechanical device using steam to strip dissolve gases from the boiler feedwater and heating the feedwater. DE-AERATION - Act of separating air from substances. DE-AERATOR - An apparatus or device which is used to remove dissolved air or oxygen from water. DE-ALKALIZATION - The removal of alkalinity from a water supply by neutralization or ion exchange. DE-ALKALIZER - An apparatus or device used to remove the alkaline carbonate and bicarbonate ions from a water supply. DE-ALLOYING - This is a corrosion process whereby one constituent of a metal alloy is preferentially removed from the alloy, leaving an altered residual microstructure. DEASHING - The removal from a solution of inorganic salts by means of adsorption by ion-exchange resins of both the cations and the anions that comprise the salts. See deionization. DE-CARBONATION - Refers to the removal of carbon dioxide from the boiler feedwater. DECIBEL (dB) - A decibel is a division of a logarithmic scale for expressing the ratio of two quantities proportional to power or energy.

The number of decibels denoting such a ratio is ten times the logarithm of the DECONCENTRATOR - This is a cylindrical tank connected before the boiler to receive the boiler feedwater before entering the boiler. It is designed to promote settling of suspended solids, which then could be removed via its own blowdown device. Was used for operation with very high suspended solids. DE-FLOCCULANT - An electrolyte adsorbed on colloidal particles in suspension that charges the particles to create repulsion forces which maintain the particles in a dispersed state, thus reducing the viscosity of the suspension. DEFROST CYCLE - Refrigerating cycle in which evaporator frost and ice accumulation is melted. DEFROST TIMER - Device connected into electrical circuit which shuts unit off long enough to permit ice and frost accumulation on evaporator to melt. DEFROSTING - Process of removing frost accumulation from evaporators. DEFROSTING CONTROL - Device to automatically defrost evaporator. It may operate by means of a clock, door cycling mechanism or during "off" portion of refrigerating cycle. DEFROSTING TYPE EVAPORATOR - Evaporator operating at such temperatures that ice and frost on surface melts during off part of operating cycle. DEGREE DAY - A unit, based upon temperature difference and time, used in estimating fuel consumption and specifying nominal heating load of a building in winter. For any one day, when the mean temperature is less than 65°F there exist as many degree days as there are Fahrenheit degrees difference in temperature between the mean temperature for the day and 65°F. DEGREES OF SUPERHEAT - The amount by which the temperature of a superheated vapor exceeds the temperature of the saturated vapor at the same pressure.

DEHUMIDIFICATION - The condensation of water vapor from air by cooling below the dewpoint or removal of water vapor from air by chemical or physical methods. DEHUMIDIFIER -(1) An air cooler or washer used for lowering the moisture content of the air passing through it; (2) An absorption or adsorption device for removing moisture from air. DEHUMIDIFYING - Removal of moisture from the air. DEHYDRATION - The removal of water vapor from air, stored goods or refrigerants. Deionization - Deionization, a more general term than deashing, embraces the removal of all charged constituents or ionizable salts (both inorganic and organic) from solution. DE-IONIZER - An apparatus or device used to remove the ions of dissolved salts from water. DEMAND - The probable maximum rate of water flow as determined by the number of water supply fixture units. DEMAND CHARGE - That part of an electric bill based on kW demand and the demand interval, expressed in dollars per kilowatt. Demand charges offset construction and maintenance of a utility's need for a large generating capacity. DEMAND CONTROL - A device which controls the kW demand level by shedding loads when the kW demand exceeds a predetermined set point. DEMAND INTERVAL - The period of time during which kW demand is monitored by a utility service, usually 15 or 30 minutes long. DEMAND LOAD - The actual amount of load on a circuit at any time. The sum of all the loads which are ON. Equal to the connected load minus the loads that are OFF. DEMAND READING - Highest or maximum demand for electricity an individual customer registers in a given interval, example, 15 minute interval. The metered demand reading sets the demand charge for the month.

DEMINERALIZER - A process to remove dissolved matter from boiler pretreated water by contacting the water with ion-exchange resins. DENSITY - The ratio of the mass of a specimen of a substance to the volume of the specimen. The mass of a unit volume of a substance. When weight can be used without confusion, as synonymous with mass, density is the weight per unit volume. DENSITY, ABSOLUTE - Mass per unit volume of a solid material, expressed usually in kg/m3. DESALINATION - The removal of inorganic dissolved solids from water. DESICCANT, LIQUID - A hygroscopic liquid, such as glycol, used to remove water from other fluids. DESICCANT - Any absorbent or adsorbent, liquid or solid, that will remove water or water vapor from a material. In a refrigeration circuit, the desiccant should be insoluble in the refrigerant. DESIGN PRESSURE - Highest or most severe pressure expected during operation. Sometimes used as the calculated operating pressure plus an allowance for safety. DESIGN PRESSURE - Highest or most severe pressure expected during operation. Sometimes used as the calculated operating pressure plus an allowance for safety. DESIGN WORKING PRESSURE - The maximum allowable working pressure for which a specific part of a system is designed. DESILICIZER - An apparatus or device used to remove silica from a water supply. DESSERT BAG - A canvas bag which permits seepage of its liquid. The liquid will evaporate and obtains the to evaporate partly from the content of the bag and thus cooling its content. DESSERT BAG - A canvas bag which permits seepage of its liquid. The liquid will evaporate and obtains the to evaporate partly from the content of the bag and thus cooling its content. DETERGENT ADDITIVE - In lubrication technology, a surface active additive that helps to keep solid particles suspended in an oil

DETERGENT CLEANING - A boiler cleaning process using an alkaline solution, primarily to remove oil and grease. DETERGENT OIL - A heavy duty oil containing a detergent additive. These oils are mainly used in combustion engines. DETERGENT-DISPERSANT - A compound mixture of cleaning agents that have both surface-active properties and suspending properties. DEW POINT - Temperature at which vapor (at 100 percent humidity) begins to condense and deposit as liquid. DEW POINT DEPRESSION - The difference between dry bulb and dew point temperatures. DEW POINT TEMPERATURE - The temperature at which condensation begins, if air is cooled at constant pressure. DIAPHRAGM - Flexible material usually made of thin metal, rubber or plastic. DIATOMACEOUS EARTH FILTRATION - Is a process in which a filter cake or precoat of diatomaceous earth is used as a filter medium. DIELECTRIC - A nonconductor of electricity. DIELECTRIC FITTING - A non conductive substance such as plastic that is placed between two dissimilar metals to prevent galvanic current flow. DIELECTRIC STRENGTH - A measure of the ability of a dielectric (insulator) to withstand a potential difference across it without electric discharge. DIFFERENTIAL - The temperature or pressure difference between cutin and cut-out temperature or pressure of a control. DIFFERENTIAL AERATION CELL - An electrolytic cell, the electromagnetic force of which is due to a difference in air (oxygen) concentration at one electrode as compared with that at another electrode of the same material. (see concentration cell)

DIFFERENTIAL SOLUTE CONCENTRATION - A potential difference between an anode and cathode on metal, because of a concentration cell due to dissolved metals. DIFFUSER - A circular, square, or rectangular air distribution outlet, generally located in the ceiling and comprised of deflecting members discharging supply air in various directions and planes, and arranged to promote mixing of primary air with secondary room air. DIRECT ACTING - Instruments that increase control pressure as the controlled variable (such as temperature or pressure) increases; while reverse acting instruments increase control pressure as the controlled variable decreases. DIRECT CURRENT - A source of power for an electrical circuit which does not reverse the polarity of its charge. DIRECT-EXPANSION EVAPORATOR - One that contains only enough liquid to continue boiling as heat is absorbed by it. DISPERSANT - A chemical which causes particulates in a water system to remain in suspension. DISPERSANT OIL - A heavy duty oil containing a dispersant additive. DISPLACEMENT PUMP - Pumps in which energy is added to the water periodically and the water is contained in a set volume. DISPLACEMENT VOLUME - The volume displaced by the piston between top dead center and bottom dead center. Dissociation - Ionization. DISSOLVED GASES - Gases soluble in water. DISSOLVED SOLIDS (TDS) - The measure of the total amount of dissolved matter. DISTILLATION - Involves boiling water and condensing the vapor. DMA - Direct memory access. A process where block of data can be transferred between main memory and secondary memory without processor intervention.

DOMESTIC HOT WATER - Potable hot water as distinguished from hot water used for house heating. DOUBLE CASING (STEAM TURBINE) DOWEL PINS - Metal pins that guarantee exact alignment of a flange joint on a horizontally split casing as found in turbine construction Down flow - Conventional direction of solutions to be processed in ionexchange column operation, that is, in at the top, out at the bottom of the column. DOWNSTREAM - The outlet side of an instrument, a pump, valve, etc.. DRAFT GAUGE - Instrument used to measure air movement by measuring air pressure differences. DRIER - Substance or device used to remove moisture from a refrigeration system. DRIERITE - Desiccant which operates by chemical action. DRIFT - Entrained water in the stack discharge of a cooling tower. DRIFT - Term used to describe the difference between the set point and the actual operating or control point. DROOP - Terms used to describe the difference between the set point and the actual operating or control point. DRUM WATER LEVEL LINE - The water level in the drum during the normal operating mode. DRY BULB - An instrument with a sensitive element to measure ambient air temperature. DRY BULB TEMPERATURE - The temperature registered by an ordinary thermometer. The dry bulb temperature represents the measure of sensible heat, or the intensity of heat. DRY COMPRESSION - The compression of vapor, in a vapor-liquid vapor-compression refrigeration cycle.

DRY ICE - Refrigerating substance made of solid carbon dioxide which changes directly from a solid to a gas (sublimates). Its subliming temperature is -78°C. DRY PIPE - A perforated or slotted pipe or box inside the drum and connected to the steam outlet. DRY STANDBY - A method of sealing al water and steam connections and placing a desiccant in the unit and applying an airtight seal. DRY SYSTEM - Refrigeration system which has the evaporator liquid refrigerant mainly in the atomized or droplet condition. DRYNESS FRACTION OR QUALITY - Weight fraction of the vapor in a vapor-liquid mixture. DUAL SHAFT GAS TURBINE - a gas turbine which has one turbine on one shaft driving the compressor and when the gas discharged from this turbine is directed to another turbine on a separate shaft to drive a load. DUAL-TEMPERATURE RE-CIRCULATING WATER SYSTEM - A closed recirculating water system that uses water either for cooling, by circulating it through a chiller, or for heating, by circulating it through a boiler or heat-exchanger depending upon need. DUCTILE GOUGING - Referring to irregular wasting of the tube metal beneath a porous deposit The micro structure of the metal does not change with this process and the ductility remains, but the thinning leads to rapture. DUCTILITY - The ability of a material to deform plastically without fracturing. DUMMY PISTON - The axial thrust in reaction turbines can be nearly eliminated by the use of balance or dummy pistons. With the correct size of a dummy piston exposed to two different bleed point pressures, the thrust is nearly equalized. There is a small leakage across the labyrinth seal of the dummy piston as steam leaks from the high to the lower bleed point DUST - An air suspension (aerosol) or particles of any solid material, usually with particle size less than 100 microns.

DYNAMIC DISCHARGE HEAD - Static discharge head plus friction head plus velocity head. DYNAMIC LOAD - An imposed force that is in motion, that is, one that may vary in magnitude, sense, and direction. DYNAMIC PUMPS - Pumps in which energy is added to the water continuously and the water is not contained in a set volume. DYNAMIC SUCTION HEAD - Positive static suction head minus friction head and minus velocity head. DYNAMIC SUCTION LIFT - The sum of suction lift and velocity head at the pump suction when the source is below pump centerline. DYNAMIC SYSTEM - An ion-exchange operation, wherein a flow of the solution to be treated is involved.

ECONOMIZER - A series of tubes located in the path of flue gases. Feed water is pumped through these tubes on its way to the boiler in order to absorb waste heat from the flue gas. EDDY CURRENT TESTING - An electromagnetic nondestructive testing method in which eddy-current flow is induced in the test object. Changes in flow caused by variations in the object are deflected into a nearby coil or coils where they are measured. EDDY CURRENTS (ELECTRICITY) - An electromagnetic nondestructive testing method in which eddy-current flow is induced in the test object. Changes in flow caused by variations in the object are deflected into a nearby coil or coils where they are measured. EDDY CURRENTS (STEAM TURBINES) - Impulse Turbine - As the steam passes through convergent nozzles, if the exit pressure is less than 0.577 x inlet pressure (the critical pressure for nozzles), eddycurrents are developed and the exit velocity will be less than calculated. EDTA - A chelating agent used with boiler water treatment. Often referred as the replacement for the phosphate-hydroxide treatment method. EFFECTIVE TEMPERATURE - Overall effect on a human of air temperature, humidity and air movement. EFFLUENT - The solution which emerges from an ion-exchange column. ELECTRIC DEFROSTING - Use of electric resistance heating coils to melt ice and frost off evaporators during defrosting. ELECTRICAL CIRCUIT - A power supply, a load, and a path for current flow are the minimum requirements for an electrical circuit. ELECTROCHEMICAL REACTIONS - A metal wasting process, due to the fluid (boiler water) being subjected to an electrical current. ELECTRODE BOILER - A boiler which generates steam or hot water by the action of immersed electrodes which conduct electricity through the boiler water, which, in turn, generates heat by its resistance to electric current.

ELECTRO DIALYSIS - This is a membrane process where an applied electric charge draws impurity ions through permeable membranes to create high purity feed water streams or low purity waste streams. ELECTROLYSIS - Chemical decomposition caused by action of an electric current in a solution. ELECTROLYTE - A chemical compound which dissociates or ionizes in water to produce a solution which will conduct an electric current; an acid, base, or salt. ELECTROMECHANICAL - Converting electrical input into mechanical action. A relay is an electromechanical switch. ELECTRO REGENERATION - Hydrogen and hydroxyl ions are formed be electrical splitting of water molecules and are swept through the unit by steady, low-voltage direct current, continuously cleansing the resin beads and carrying away the unwanted salts ELEMENT - A pure substance that cannot be broken down by chemical means to a simpler substance. ELEVATION HEAD - The energy possessed per unit weight of a fluid because of its elevation. ELUTION - The stripping of adsorbed ions from an ion-exchange material by the use of solutions containing other ions in concentrations higher than those of the ions to be stripped. Emissions: The gases and airborne particles produced during Combustion. EMULSION - A colloidal dispersion of one liquid in another. ENDOTHERMIC REACTION - Pertaining to a chemical reaction which is accompanied by an absorption of heat. ENERGY - Expressed in kilowatt-hours (kWh) or watt hours (Wh), and is equal to the product of power and time. ENERGY - In the simplest terms, energy is the ability to perform work. It may exist in several forms, such as heat energy, mechanical energy, chemical energy, or electrical energy, and may be changed from one form to another.

ENERGY - The ability to do work. Energy can exist in one of several forms, such as heat, light, mechanical, electrical or chemical. Energy can neither be created nor destroyed, but can be transferred from one form to another. Energy can also exist in one of two states, either potential or kinetic. ENERGY (CONSUMPTION) CHARGE - That part of an electric bill based on kWh consumption (expressed in cents per kWh). Energy charge covers cost of utility fuel, general operating costs, and part of the amortization of the utility's equipment. Energy = power x time ( 1 ) Expressed in kilowatt-hours (kWh) or watt hours (Wh), and is equal to the product of power and time. ( 2 ) The ability to do work. Energy can exist in one of several forms, such as heat, light, mechanical, electrical or chemical. Energy can neither be created nor destroyed, but can be transferred from one form to another. Energy can also exist in one of two states, either potential or kinetic. ENGINE - Prime mover; device for transforming fuel or heat energy into mechanical energy. ENGINE OIL - An oil used to lubricate an internal combustion engine. ENTHALPY - The total quantity of heat energy contained in a substance, also called total heat; the thermodynamic property of a substance defined as the sum of its internal energy plus the quantity Pv/J, where P = pressure of the substance, v = its volume, and J = the mechanical equivalent of heat. ENTRAINMENT - The transport of water into a gas stream. In a boiler, this is carryover, in a cooling tower, drift. ENTRAINMENT (HVAC) - The capture of part of the surrounding air by the air stream discharged from an outlet (some times called secondary air motion). ENTROPY - A thermodynamic measure of the amount of energy unavailable for useful work in a system undergoing change. The ratio of the heat added to a substance to the absolute temperature at which it is added.

ENVIRONMENT - The aggregate of all conditions (such as contamination, temperature, humidity, radiation, magnetic and electric fields, shock, vibration) that externally influence the performance of a material or component. EPSON SALT - Magnesium sulfate. EQUALIZING HOLE (STEAM TURBINE) - A hole in the turbine disc designed to equalize axial thrust with impulse bladed turbines. EQUILIBRIUM REACTIONS - The interaction of ionizable compounds in which the products obtained tend to revert to the substance from which they were formed until a balance is reached in which both reactants and pacts are present in definite ratios. EQUIVALENT WEIGHT - Refers to the amount of an element combining with a unit weight of hydrogen. In terms of water treatment, a method used to calculate the concentration of a given ion in terms of its calcium carbonate. EROSION , ABRASIVE - Erosive wear caused by relative motion of solid particles which are present in fluids and are moving parallel to a solid surface. EROSION, CAVITATION - Progressive loss of original material from a solid surface due to continuing exposure to cavitation. EROSION, IMPINGEMENT - Loss of material from a solid surface due to liquid impingement. EROSION, LIQUID - Removal of films or metal by mechanical action and corrosion of active metal. EROSION-CORROSION - A conjoint action involving corrosion and erosion in the presence of a moving corrosive fluid, leading to the accelerated loss of material. ETHANE (R-170) - Refrigerant sometimes added to other refrigerants to improve oil circulation. EUTECTIC - An isothermal reversible reaction in which a liquid solution is converted into two or more intimately mixed solids on cooling. EUTECTIC POINT - Freezing temperature for eutectic solutions.

EVACUATION - The removal of gases from a system. EVAPORATION - The change of state from liquid to vapor, for example as water evaporates to a vapor in a cooling tower. EVAPORATIVE CONDENSER - A condenser which has water flowing over coils containing the refrigerant gas which is thus cooled and condensed by evaporation of that water. EVAPORATIVE CONDENSER - Device which uses open spray or spill water to cool a condenser. Evaporation of some of the water cools the condenser water and reduces water consumption. EVAPORATIVE COOLING - The adiabatic exchange of heat between air and a water spray or wetted surface. The water approaches the wetbulb temperature of the air, which remains constant during its traverse of the exchanger. EVAPORATOR - The heat exchanger in which the medium being cooled, usually air or water, gives up heat to the refrigerant through the exchanger transfer surface. The liquid refrigerant boils into a gas in the process of the heat absorption. EVAPORATOR FAN - Fan which increases airflow over the heat exchange surface of evaporators. EVAPORATOR PRESSURE REGULATOR - Automatic pressure regulating valve mounted in suction line between evaporator outlet and compressor inlet. Its purpose is to maintain a predetermined pressure and temperature in the evaporator. EVAPORATOR, FLOODED - Evaporator containing liquid refrigerant at all times. EXFlLTRATION - The flow of air outward from a space through walls, leaks, etc. EXFOLIATION - Scaling off of a surface in flakes or layers as the result of corrosion. EXHAUSTION - The state in which the adsorbent is no longer capable of useful ion exchange; the depletion of the exchanger's supply of available ions. The exhaustion point is determined arbitrarily in terms of (1) a value in parts per million of ions in the effluent solution; and

(2) the reduction inequality of the effluent water determined by conductivity bridge which measures the resistance of the water to the flow of an electric current. EXOTHERMIC - Chemical reaction in which heat is released. EXPANSION JOINT - Device in piping designed to allow movement of the pipe caused by the pipe's expansion and contraction. EXPANSION TANK - A reservoir usually above a closed re-circulating water system that is blanketed with a gas to permit expansion and contraction of water in the system during temperature changes. EXPANSION VALVE - Device in refrigerating system which reduces the pressure from the high side to the low side and is operated by pressure. EXPANSION VALVE, CAPILLARY TUBE - A tube of small internal diameter used as liquid refrigerant flow control and pressure reducer between high and low sides. Also used to transmit pressure from the sensitive bulb of some temperature controls to the operating element. EXPANSION VALVE, THERMOSTATIC - Control valve operated by temperature and pressure within evaporator. It controls flow of refrigerant. Control bulb is attached to outlet of evaporator. EXPENDABLE REFRIGERANT SYSTEM - System, which discards the refrigerant after it has evaporated. EXTERNAL DRIVE - Term used to indicate a compressor driven directly from the shaft or by a belt using an external motor. Compressor and motor are serviceable separately. EXTERNAL EQUALIZER - Tube connected to low-pressure side of a thermostatic expansion valve diaphragm and to exit end of evaporator. EXTERNAL TREATMENT - Refers to the treatment of water before it enters the boiler. EXTRACTION TURBINE – are turbines where steam is extracted at one or more points at constant pressure. Extraction turbines may be single or double-extraction-condensing turbines or single-or doubleextraction back-pressure turbines. The extracted steam is used for

process. Do not call these bleed turbines where steam is used for heating feed water.

Face Area: The total plane area of the portion of a grille, coil, or other items bounded by a line tangent Fahrenheit: A thermometric scale in which 32 (¡F) denotes freezing and 212 (¡F) the boiling point of water under normal pressure at sea level (14.696 psi). FAIL SAFE - In load management, returning all loads to conventional control during a power failure. Accomplished by a relay whose contacts are normally closed. FAILURE - A rupture, break, or disintegration of a metal or part of an HVAC system. FALSE BRINELING - Damage to a solid bearing surface characterized by indentations not caused by plastic deformation resulting from overload, but thought to be due to other causes such as fretting corrosion. FAN PERFORMANCE CURVE - Fan performance curve refers to the constant speed performance curve. This is a graphical presentation of static or total pressure and power input over a range of air volume flow rate at a stated inlet density and fan speed. It may include static and mechanical efficiency curves. The range of air volume flow rate which is covered generally ex tends from shutoff (zero air volume flow rate) to free delivery (zero fan static pressure). The pressure curves are generally referred to as the pressure-volume curves. FAN TUBE AXIAL - A propeller or disc type wheel within a cylinder and including driving mechanism supports for either belt drive or direct connection. FAN, CENTRIFUGAL - A fan rotor or wheel within a scroll type housing and including driving mechanism sup ports for either belt drive or direct connection. FAN, PROPELLER - A propeller or disc type wheel within a mounting ring or plate and including driving mechanism supports for either belt drive or direct connection. FAN, VANE AXIAL - A disc type wheel within a cylinder, a set of air guide vanes located either before or after the wheel and including driving mechanism supports for either belt drive or direct connection.

FARAD - A unit of electric capacity, designated by F. FATIGUE - The phenomenon leading to fracture under repeated or fluctuating stresses having maximum value less than the ultimate strength of the material. FAULT - A short circuit either line to line, or line to ground. FEED WATER - Water which is fed to a system such as a boiler or cooling tower. FEED WATER LINE - The piping leading to a system through which the feed water flows. FEED WATER HEATER - A device used to heat feed water with steam. FERRIC COAGULANT - Ferric sulfate Fe2(SO4)3 act to precipitate ferric hydroxide, coagulate at 4.0 - 11.0 pH range. FERRIC HYDROXIDE - The complete reaction product of iron, water, and oxygen, which forms a red precipitate in water [Fe(OH)3] FERRIC ION - An iron atom that has a positive electric charge of +3. (Fe2+) FERROUS - Metallic materials in which the principle component is iron. FERROUS HYDROXIDE - The reaction product of iron and water in the absence of oxygen; it remains soluble in the water [Fe(OH)2]. FERROUS ION - An iron atom that has a positive electric charge of + 2(Fe2+). FILMING AMINES - Amines that form a impervious non-wettable film, which acts as a barrier between the metal and the condensate and provide protection against carbon dioxide and oxygen. These amines do not neutralize carbon dioxide. FILTER - A device to remove solid material from a fluid. FILTER-DRIER - A combination device used as a strainer and moisture remover.

FILTRATION - Is the process of passing a liquid containing suspended matter through a suitable porous material in such a manner as to effectively remove the suspended matter from the liquid. FIN - An extended surface to increase the heat transfer area, as metal sheets attached to tubes. FIRE POINT - The temperature at which a material will continue to burn for at least 5 seconds without the benefit of an outside flame. FIRE TUBE - A tube, in a boiler, through which the hot gases flow and transfer heat to the water on the outside of the tube. FIRE WALL - The back end of a boiler, opposite the burner, at which the hot gases change direction of flow. FIREBRICK - A refractory brick, often made from fire clay, that is able to withstand temperature in the range of 1500 to 1600°C, and is used to line furnaces. FIXED DISPLACEMENT PUMP - A pump in which the displacement per cycle cannot be varied. FLASH - The portion of a superheated fluid converted to vapor when its pressure is reduced. FLASH CHAMBER - A separating tank placed between the expansion valve and the evaporator to separate and bypass any gas formed in the expansion valve. FLASH GAS - The gas resulting from the instantaneous evaporation of refrigerant in a pressure-reducing device to cool the refrigerant to the evaporating temperature obtaining at the reduced pressure. FLASH POINT - The temperature at which a material to give off sufficient vapor to form a flammable mixture. FLASH TANK - A vessel used for separating the liquid phase from the gaseous phase formed from a rise in temperature and/or a reduction of pressure on the flowing stream. FLASHING - Evaporation of a liquid into a vapor. FLEXIBLE GEAR COUPLING -

Floating Action Controllers: Essentially two position type controllers which vary the position of the controlled devices but which are arranged to stop before reaching a maximum or minimum position. FLOCCULANTS - An electrolyte added to a colloidal suspension to cause the particles to aggregate and settle out as the result of reduction in repulsion between particles. FLOCCULATION - The process of agglomerating coagulated particles into settable flocs, usually of a gelatinous nature. FLOOD BACK - The condition of liquid refrigerant returning, usually from an overfed evaporator, to the compressor through the suction line. FLOTATION - A process of separating solids from water by developing a froth. FLOW RATE - The volume of solution which passes through a given quantity of resin within a given time. Flow rate is usually expressed in terms of feet per minute per cubic foot of resin or as milliliters per minute per milliliter of resin. FLOW, LAMINAR OR STREAMLINE - Fluid flow in which each fluid particle moves in a smooth path substantially parallel to the paths followed by all other particles. FLOW, TURBULENT - Fluid flow in which the fluid moves transversely as well as in the direction of the tube or pipe axis, as opposed to streamline or viscous flow. FLUID - The general term that includes gas, vapor or liquid FLUID HEAD - The static pressure of fluid expressed in terms of the height of a column of the fluid, or of some manometric fluid, which it would support. FLUIDIZED BED - A contained mass of finely divided solid that behaves like a fluid when brought into suspension in a moving gas. FLY ASH - A finely divided siliceous material formed during the combustion of coal, coke, or other solid fuels.

FOAM CARRYOVER - Is the development of excessive moisture in the steam from carryover of foam from the drum. Usually common in low pressure boilers due to high concentration of dissolved solids. FOAMING - Formation of steam bubbles on the surface of the boiler water due to high surface tension of the water. FORCE - The action on a body which tends to change its relative condition as to rest or motion. FORCE PUMP - A device used to inject a solution into a closed system through an opening such as a drain valve. FORCED CONVECTION - Movement of fluid by mechanical force such as fans or pumps. FORCED DRAFT COOLING TOWER - Cools water by mechanically forcing air through the tower. FORCE-FEED OILING - Lubrication system which uses a pump to force oil to surfaces of moving parts. FOULING - Deposits of impurities, dirt or foreign matter that clog systems or restrict flow and interfere with heat transfer. FOULING FACTOR - The degree of interference with heat transfer. FREEBOARD - The space provided above the resin bed in an ionexchange column to allow for expansion of the bed during backwashing. FREEZER - A refrigerating device designed to lower the temperature below 0°C. FREEZER BURN - Condition applied to food which has not been properly wrapped and that has become hard, dry and discolored. FREEZE-UP - (1) Formation of ice in the refrigerant control device which may stop the flow of refrigerant into the evaporator. (2) Frost formation on an evaporator which may stop the airflow through the evaporator. FREEZING - Change of state from liquid to solid.

FREEZING POINT - The temperature at which a liquid becomes solid. FREON - Trade name for a family of synthetic chemical refrigerants. FRESH WATER - Water that has little or no salt dissolved in it. FRICTION - Friction is the resistance found at the duct and piping walls. Resistance creates a static pressure loss in systems. The primary purpose of a fan or pump is to produce a design volume of fluid at a pressure equal to the frictional resistance of the system and the other dynamic pressure losses of the components. FRICTION HEAD - The pressure in psi or feet of the liquid pumped which represents system resistance that must be overcome. FRIGORIFIC MIXTURE - Are substances used in laboratory methods of producing a drop in temperature. A common example is a mixture of snow and salt. FROST - Frozen condensation. FROST BACK - Condition in which liquid refrigerant flows from evaporator into suction line; usually indicated by sweating or frosting of the suction line. FROST CONTROL - Semiautomatic - Control which starts defrost part of a cycle manually and then returns system to normal operation automatically. FROST FREE REFRIGERATOR - Refrigerated cabinet which operates with an automatic defrost during each cycle. FROSTING TYPE EVAPORATOR - Refrigerating system which maintains the evaporator at frosting temperatures during all phases of cycle. FREQUENCY - The number of vibrations, waves, or cycles of any periodic phenomenon per second. In architectural acoustics, the interest lies in the audible frequency range of 20 to 20000 cps Hertz (cycles per second). FUEL KNOCK - A hammer like noise produced when fuel is not burned properly in a cylinder. FULL LOAD CURRENT - See Running Current.

FUMES - Solid particles commonly formed by the condensation of vapors from normally solid materials such as molten metals. Fumes may also be formed by sublimation, distillation, calcinations, or chemical reaction wherever such processes create airborne particles predominantly below one micron in size. Such solid particles sometimes serve as condensation nuclei for water vapor to form smog. FUNGUS - A lower form of plant life which does not contain chlorophyll, for example, a mold. FUSIBLE PLUG - Plug or fitting made with a metal of a known low melting temperature. Used as safety device to release pressures in case of fire.

GAGE PRESSURE - Absolute pressure minus atmospheric pressure. GALVANIC ACTION - Wasting away of two unlike metals due to electrical current passing between them. The action is increased in the presence of moisture. GALVANIC CELL - Electrolytic brought about by the difference in electric potential between two dissimilar metals. GALVANIC COUPLE - The connection of two dissimilar metals in an electrolyte that results in current flow through the circuit. GALVANIZING - The coating of metal with another by an electrolytic process; for example, electrolytically zinc-coat steel is called galvanized steel. GAS - Usually a highly superheated vapor which, within acceptable limits of accuracy, satisfies the perfect gas laws. GAS - Vapor phase or strata of a substance. GAS CONSTANT - The coefficient "R" in the perfect gas equation: PV = MRT. GAS LUBRICATION - A system of lubrication in which the shape and relative motion of the sliding surfaces cause the formation of a gas film having sufficient pressure to separate the surfaces. GAS REFRIGERATION CYCLE - Where the refrigerant remains in the gaseous phase throughout. GAS TURBINE - An engine in which gas , under pressure is formed by combustion, is directed against a series of turbine blades. The energy in the expanding gas is converted into rotary motion. GAS TURBINE COMPRESSOR - a compressor designed foe the use with gas turbine installations. This could be centrifugal or an axial compressor. GAS VALVE - Device in a pipeline for starting, stopping or regulating flow of gas.

GAS, INERT - A gas that neither experiences nor causes chemical reaction nor undergoes a change of state in a system or process; e.g., nitrogen or helium mixed with a volatile refrigerant. GASIFICATION - When a substance is converted to become a gas. GASKET - A device, usually made of a deformable material, that is used between two relatively static surfaces to prevent leakage. GAUGE MANIFOLD - Chamber device constructed to hold both compound and high-pressure gauges. Valves control flow of fluids through. GAUGE VACUUM - Instrument used to measure pressures below atmospheric pressure. GENERAL CORROSION - Uniform overall corrosion of metal surfaces. GENERATING TUBE - A boiler tube used for evaporation. GENERATOR - A machine that changes that changes mechanical energy into electrical energy. GFI, GFCI - Ground fault (circuit) interrupter - a device that senses ground faults and reacts by opening the circuit. GRAIN - A unit of weight; 0.0648 grams; 0.000143 pounds. GRAIN BOUNDARIES - Referring to the junction of crystallites. GRAINS OF MOISTURE - The unit of measurement of actual moisture contained in a sample of air. (7000 grains - one pound of water). GRAINS PER GALLON - A unit of concentration. 1 gr/gal = 17.1 mg/L. GRAM - A unit of weight; 15.432 grains; 0.0022 pounds. GRAM-MILLIQUIVALENTS - The equivalent weight in grams, divided by 1000. GRAVITY - The attraction exerted by the earth’s mass on objects at its surface. GRAVITY, SPECIFIC - Density compared to density of standard material; reference usually to water or to air.

GREASE - A lubricant composed of an oil thickened with a soap or other thickener to a solid or semisolid consistency. GREASE, BLOCK - A grease that is sufficiently hard to retain its shape in block or stick form. GREASE, SODA BASED - A grease prepared from lubricating oil and sodium soap. GREEN LIQUOR - The liquor resulting from dissolved molten smelt from Kraft recovery furnace in water. GREENSAND - Naturally occurring materials, composed primarily of complex silicates, which possess ion-exchange properties. GROOVING - A form of deterioration of boiler plate by a combination of localized corrosion and stress concentration. GROUND - Zero voltage, or any point connected to the earth or "ground". GROUND BED - Cathodic protection, an interconnected group of impressed-current anodes that absorbs the damage caused by generated electric current GROUND BUS - A busbar in a panel or elsewhere, deliberately connected to ground. GROUND COIL - Heat exchanger buried in the ground. May be used either as an evaporator or as a condenser. GROUND CONDUCTOR - Conductor run in an electrical system, which is deliberately connected to the ground electrode. Purpose is to provide a ground point throughout the system. Insulation color green. Also called "green ground". GROUND FAULT - An unintentional connection to ground. GROUT - To force sealing material into a soil, sand or confined small space; or the sealing material used in grouting.

HAC - Hydrogen- assist cracking. HALIDE LEAK DETECTOR - A device used to detect vapor leaks of halogen refrigerants. It uses acetylene as its base. HALIDE REFRIGERANTS - Family of refrigerants containing halogen chemicals. HALIDE TORCH - Type of torch used to safely detect halogen refrigerant leaks in system. HALOGENS - Substance containing fluorine, chlorine, bromine and iodine. HARD WATER - Water that contains dissolved compounds of calcium, magnesium or both. HARDNESS - Are generally referred to the presence of calcium and magnesium content of the water. HARDNESS - The scale-forming and lather-inhibiting qualities which water, high in calcium and magnesium ions, possesses. HARDNESS CONTROL - An action designed to remove hardness and at the same time to produce an equivalent amount of suspended solids. HARDNESS OF CALCIUM CARBONATE - The expression ascribed to the value obtained when the hardness-forming salts are calculated in terms of equivalent quantities of calcium carbonate; a convenient method of reducing all salts to a common basic for comparison. HEAD - Pressure, usually expressed in feet of water, inches of mercury or millimeters of mercury. Head - The measure of the pressure of water expressed in feet of height of water: 1 psi = 2.31 feet of water. HEAD DYNAMIC OR TOTAL - In flowing fluid, the sum of the static and velocity heads at the point of measurement. HEAD PRESSURE - Pressure which exists in condensing side of refrigerating system.

HEAD PRESSURE CONTROL - Pressure-operated control which opens electrical circuit if high-side pressure becomes too high. HEAD STATIC - The static pressure of fluid expressed in terms of the height of a column of the fluid, or of some manometric fluid, which it would support. HEAD VELOCITY - Height of fluid equivalent to its velocity pressure in flowing fluid. HEADER - Length of pipe or vessel to which two or more pipe lines are joined carries fluid from a common source to various points of use. HEADLOSS - The loss of energy as a result of friction; commonly expressed in feet. HEAT - Form of energy which acts on substances to raise their temperature; energy associated with random motion of molecules. HEAT CAPACITY - The amount of heat necessary to raise the temperature of a given mass one degree. Numerically, the mass multiplied by the specific heat. HEAT CONDUCTOR - A material capable of readily conducting heat. The opposite of an insulator or insulation. HEAT ENGINE - Mechanical devices which convert heat to work, such as the steam boiler, gas turbine, solar energy, refrigerators, steam engines, steam turbines. HEAT EXCHANGER - Device used to transfer heat from a warm or hot surface to a cold or cooler surface. (Evaporators and condensers are heat exchangers.) HEAT LAG - The time it takes for heat to travel through a substance heated on one side. HEAT LEAKAGE - Flow of heat through a substance. HEAT OF COMPRESSION - Mechanical energy of pressure changed into energy of heat. HEAT OF CONDENSATION - The latent heat given up by a substance as it changes from a gas to a liquid.

HEAT OF FUSION - The latent heat absorbed when a substance changes from a solid state to a liquid state. HEAT OF RESPIRATION - Process by which oxygen and carbohydrates are assimilated by a substance; also when carbon dioxide and water are given off by a substance. HEAT OF VAPORIZATION - The latent heat absorbed by a substance as it changes from a liquid to a vapor. HEAT PIPE - A refrigeration device with no moving parts, but containing a refrigerants. HEAT PUMP - A device used to transfer heat from a low temperature to a high temperature medium also a reversed cycle in which work is the input and heat is rejected to a sink at a higher temperature than the source. HEAT PUMP - A refrigerating system employed to transfer heat into a space or substance. The condenser provides the heat while the evaporator is arranged to pick up heat from air, water, etc. By shifting the flow of air or other fluid, a heat pump system may also be used to cool the space. HEAT SINK - Relatively cold surface capable of absorbing heat. HEAT TRANSFER - Flow of heat by conduction, convection and radiation. HEAT TRANSFER - Movement of heat from one body or substance to another. Heat may be transferred by radiation, conduction, convection or a combination of these three methods. HEAT, SENSIBLE - Heat which is associated with a change in temperature; specific heat exchange of temperature; in contrast to a heat interchange in which a change of state (latent heat) occurs. Heat, Specific- The ratio of the quantity of heat required to raise the temperature of a given mass of any substance one degree to the quantity required to raise the temperature of an equal mass of a standard substance (usually water at 59 F) one degree.

Heat, Total (Enthalpy) - The sum of sensible heat and latent heat between an arbitrary datum point and the temperature and state under consideration. HEAT-EXCHANGER MATERIALS - The metals or materials of construction of a heat exchanger. HEAT-TRANSFER MEDIUM - The fluid, often water, which acts as the agent or medium in a heat exchanger through which heat is exchanged from one side to the other. HEATING COIL - Heat transfer device consisting of a coil of piping, which releases heat. HEATING CONTROL - Device which controls temperature of a heat transfer unit which releases heat. HEATING SURFACE - That surface which is exposed to the heating medium for absorption and transfer of heat to the medium. HENRY’S LAW - An expression for calculating the solubility of a gas in a fluid based on temperature and partial pressure. HENRY - The unit of self-inductance or mutual inductance in the metric system. Its symbol is H.HERMETIC - Sealed so that the object is gas tight. HERMETIC COMPRESSOR - Compressor which has the driving motor sealed inside the compressor housing. The motor operates in an atmosphere of the refrigerant. HERMETIC MOTOR - Compressor drive motor sealed within same casing which contains compressor. HERMETIC SYSTEM - Refrigeration system which has a compressor driven by a motor contained in compressor dome or housing. HERTZ - A unit in the metric system used to measure frequency in cycles per second. Its symbol is Hz.HIC - Hydrogen-induced cracking. (Same as hydrogen embrittlement)

HIDDEN DEMAND CHARGE - Electric bill charges that are based on cents per kWh per kW demand contain a hidden demand charge. A low load factor for a building then penalizes the energy user through this "hidden" charge. HIDEOUT - Is the accumulation of chemicals on surfaces, in crevices or in deposits within the system during normal operation. HIGH LIMIT CONTROL - A device which normally monitors the condition of the controlled medium and interrupts system operation if the monitored condition be comes excessive, for example a high level of fluid in a storage tank. HIGH SIDE - Parts of the refrigerating system subjected to condenser pressure or higher; the system from the compression side of the compressor through the condenser to the expansion point of the evaporator. HIGH-PRESSURE CUT-OUT - Electrical control switch operated by the high-side pressure which automatically opens electrical circuit if too high pressure is reached. HIGH-SIDE FLOAT - Refrigerant control mechanism which controls the level of the liquid refrigerant in the high-pressure side of mechanism. HIGH-VACUUM PUMP - Mechanism which can create a vacuum in the 1000 to 1 micron range. HOT DECK - The heating section of a multizone system. HOT GAS BYPASS - Piping system in refrigerating unit which moves hot refrigerant gas from condenser into low-pressure side. HOT GAS DEFROST - Defrosting system in which hot refrigerant gas from the high side is directed through evaporator for short period of time and at predetermined intervals in order to remove frost from evaporator. HOT JUNCTION - That part of thermoelectric circuit which releases heat. HOT PROCESS - A water treatment process, when the water is heated above the room temperature. HOT PROCESS PHOSPHATE SOFTENING - A process whereby the calcium and magnesium salts containing, constituting the hardness of

water, are chemically precipitated and removed with phosphate in conjunction with caustic soda. HOT WELL - A tank used to receive condensate from various sources on its passage back to the boiler through a feedwater system. HOT-WATER HEATING BOILER - A boiler in which no steam is generated and from which hot water is circulated for heating purposes and then returned to the boiler. HOT-WATER RE-CIRCULATING SYSTEM - A heating system using water as a heat-transfer medium through a heat exchanger or boiler to terminal heating unit. HSC - Hydrogen stress cracking. HSCC - Hydrogen- assisted stress-corrosion cracking. HUMIDIFIER - A device to add moisture to air. HUMIDIFYING - Adding of moisture to the air. HUMIDIFYING EFFECT - The latent heat of vaporization of water at the average evaporating temperature times the weight of water evaporated per unit of time. HUMIDISTAT - A regulatory device, actuated by changes in humidity, used for the automatic control of relative humidity. HUMIDITY - Dampness of air. HUMIDITY RATIO - The ratio of the mass of the water vapor to the mass of dry air contained in the sample. HUMIDITY, ABSOLUTE - The weight of water vapor per unit volume. HUMIDITY, PERCENTAGE - The ratio of the specific humidity. HUMIDITY, RELATIVE - The ratio of the mol fraction of water vapor present in the air, to the mol fraction of water vapor present in saturated air at the same temperature and barometric pressure; approximately, it equals the ratio of the partial pressure or density of the water vapor in the air, to the saturation pressure or density, respectively, of water vapor at the same temperature.

HUNTING - A surge of engine speed to higher number of revolutions per minute, followed by a drop to normal engines speed without manual movement of the throttle. Is often caused by a faulty or improperly adjusted governor. HVAC - Heating, Ventilating, and Air Conditioning. HVAC BOILER - Boiler for heating or air conditioning (Absorption Refrigeration) HVAC EQUIPMENT - Apparatus or equipment used in heating, ventilating, and air conditioning. HYDRATION - Absorption of water by a mineral that results in a change in the nature of the mineral. HYDRAULIC CLASSIFICATION - The rearrangement of resin particles in an ion-exchange unit. As the backwash water flows up through the resin bed, the particles are placed in a mobile condition wherein the larger particles settle and the smaller particles rise to the top of the bed. HYDRAULIC COUPLING - A fluid connection between a prime mover and the machine it drives. It uses the action of liquid moving against blades to drive the machine. HYDRAULIC HEAD - The force exerted by a column of liquid expressed by the height of the liquid above the point at which the pressure is measured. Although head refers to a distance or height, it is used to express pressure, since the force of the liquid column is directly proportional to its height. Also called head or hydrostatic head. HYDROCARBONS - Organic compounds containing only hydrogen and carbon atoms in various combinations. HYDROGEN COOLED GENERATOR - High performance is provided by effective cooling and loss reduction. HYDROGEN CYCLE - A complete course of cation-exchange operation in which the adsorbent is employed in the hydrogen or free acid form. HYDROGEN DAMAGE - A type of corrosion occurring beneath a relative dense deposit. This type of damage can only occur if hydrogen was present in the metal. Failure takes place at thick edges in the form of

fracture, rather then thinning. Hydrogen produces the corrosion reaction, moving into underlying metal, causing decarburization and intergranular fissuring of the structure. Damages usually result in larger pieces of metal being blown away, rather then just bursting. HYDROGEN INDUCED CRACKING - Caused by the introduction of hydrogen during the welding process. HYDROGEN ION - A portion of the molecule of water containing one atom of hydrogen which has a positive electric charge. HYDROGEN-ION CONCENTRATION - The degree or quantity of hydrogen ions in a water solution. HYDROLOGIC CYCLE - The cycle of water from evaporation through condensation to precipitation. HYDROLYSIS - A chemical reaction between a mineral and water that results in dissolution of the mineral. HYDROMETER - Floating instrument used to measure specific gravity of a liquid. HYDRONIC SYSTEM - A re-circulating water system used for heating and/or comfort cooling. HYDROPHILIC - Having an affinity for water. HYDROSTATIC PRESSURE - The pressure at any point in a liquid at rest; equal to the depth of the liquid multiplied by its density. Hydroxyl - The term used to describe the anionic radical (OH-) which is responsible for the alkalinity of a solution. HYGROMETER - Instrument used to measure degree of moisture in the atmosphere. HYGROSCOPIC - Ability of a substance to absorb and release moisture and change physical dimensions as its moisture content changes.

ICE CREAM CABINET - Commercial refrigerator which operates at approximately -18°C; used for storage of ice cream. IGNITION QUALITY - The ability of a fuel to ignite when it is injected into the compressed-air charge in a diesel cylinder. It is measured by an index called the cetane number. IMMISCIBLE - Not capable of mixing (as oil and water). IMPEDANCE (Z) - The quantity in an AC circuit that is equivalent to resistance in a DC circuit, inasmuch as it relates current and voltage. It is composed of resistance plus a purely AC concept called reactance and is expressed, like resistance, in ohms. IMPELLER - A rotating set of vanes designed to impart rotation to a mass of fluid. IMPINGEMENT - High-velocity flow of water or gas over a metal surface, causing premature failure by abrasion. IMPULSE PRINCIPLE INDUCTANCE - The process when a second conductor is placed next to a conductor carrying AC current (but not touching it), the everchanging magnetic field will induce a current in the second conductor. INDUCTION - The capture of part of the ambient air by the jet action of the primary air stream discharging from a controlled device. INDUCTION HEATING - Heating by combined electrical resistance and hysteresis losses induced by subjecting a metal to varying magnetic field surrounding a coil carrying alternating current. INDUCTIVE LOADS - Loads whose voltage and current are out-ofphase. True power consumption for inductive loads is calculated by multiplying its voltage, current, and the power factor of the load. INDUCTOR - A fundamental element of electrical systems constructed of numerous turns of wire around a ferromagnetic or air core. INERT GAS - A gas that does not readily enter into or cause chemical reactions. INFILTRATION - Air flowing inward as through a wall, crack, etc.

INFLUENT - The solution which enters an ion-exchange unit. INHIBITOR - An additive used to retard undesirable chemical action in a product. It is added in small quantities to gasoline’s to prevent oxidation and gum formation, to lubricating oils to stop color change, and to corrosive environments to decrease corrosive action. INORGANIC MATERIAL - Are substances not derived from living things. INRUSH CURRENT - The current that flows the instant after the switch controlling current flow to a load is closed. Also called "locked rotor current". INSTANTANEOUS RATE - Method for determining when load shedding should occur. Actual energy usage is measured and compared to a present kilowatt level. If the actual kilowatt level exceeds a designated set point, loads will be shed until the actual rate drops below the set point. INSULATION, THERMAL - Material which is a poor conductor of heat; used to retard or slow down flow of heat through wall or partition. INSULATOR - A material of such low electrical conductivity that a flow of current through it can usually be neglected. Similarly, a material of low thermal conductivity, such as that used to insulate structures. INTERCOOLED CYCLE - Refers to a gas turbine employing two compressors. The compressed air from the first compressor is cooled before being discharged to second compressor. INTERCOOLING - Removal of heat from compressed gas between the compression stages. INTERGRANULAR CRACKING - Cracking or fracturing that occurs between the grains or crystal in a polycrystalline aggregate. Also called intercrystalline cracking. Contrast with Tran granular cracking. INTERMITTENT BLOWDOWN - The blowdown is taken from the mud drum, waterwall headers or the lowest point of circulation. INTER-STAGE DIFFERENTIAL - In a multistage HVAC system, the change in temperature at the thermostat needed to turn additional heating or cooling equipment on.

ION - An atom or radical in solution carrying an integral electric charge, either positive (cat ion) or negative (anion). ION EXCHANGE - A reversible process by which ions are interchanged between solids and a liquid. ION EXCHANGE RESIN - Cross linked polymers that form salts within ions from aqueous solutions. IONIC STRENGTH - A measure of strength of a solution based on both the concentrations and valences of the ions present. IONIZATION - The process of separation of a molecule into its electrically charged atoms or parts. IRON - A metallic element found as an impurity in water in very small amounts. Also a metal which is widely used in the construction of HVAC and plumbing equipment; the major component of steel. IRON BACTERIA - Are filamentous organisms encountered in ironbearing water. ISENTROPIC PROCESS - A process carried out reversibly without energy interchange as heat. Also a processes carried out with no entropy change. ISOBARIC PROCESS - A process carried out at constant pressure. ISOCHORIC PROCESS OR ISOMETRIC- A process during which the specific volume remains constant. ISOMETRIC PROCESS - A process carried out at constant volume. ISOTHERMAL - Changes of volume or pressure under conditions of constant temperature. ISOTHERMAL EXPANSION AND CONTRACTION - Action which takes place without a temperature change. ISOTHERMAL PROCESS - For a constant temperature process involving an ideal gas,

JACKING OIL PUMP - provides oil supply when the turbine is placed on barring (slow rotation to stop the turbine from sagging or hogging) JET COMPRESSOR - A device employing a venture tube so that a high pressure stream flowing through the nozzle creates a lower pressure or a vacuum into which the gas to be compressed flows. The gas is discharged from the nozzle with the expanded high-pressure medium. JOULE - English Scientist James Prescott Joule (1818 - 1889) JOULE - The unit used to measure heat, work, and energy in the metric system. Its symbol is J. It is the amount of energy required to move an object of 1 kg mass to a height of 1 m. Also called a newtonmetre. JOULE-THOMSON EFFECT - The change in gas temperature which occurs when the gas is expanded adiabatically from a higher pressure to a lower pressure. The effect for most gases, except hydrogen and helium, is a cooling of the gas. JOURNAL - That part of a shaft or axle that rotates relative to a radial bearing.

KATA THERMOMETER - Large-bulb alcohol thermometer used to measure air speed or atmospheric conditions by means of cooling effect. KELVIN SCALE (K) - Thermometer scale on which unit of measurement equals the Celsius degree and according to which absolute zero is 0 degree, the equivalent of -273.16°C. Water freezes at 273.16 K. and boils at 373.16 K. The relationship - TK = TC + 273.16 KEROSENE - a light, hydrocarbon fuel or solvent. KILO CALORIE - This is the amount of heat (energy) necessary to raise the temperature of 1 kg of water 1°C. (Kilo calorie = kcal) KILO CALORIE - This is the amount of heat (energy) necessary to raise the temperature of 1 kg of water 1°C. (Kilo calorie = kcal) KILO GRAIN - A unit of weight; 1000 grains. KILOVOLT AMPERE - Product of the voltage times the current. Different from kilowatts because of inductive loads in an electrical system. Abbreviated: KVA kilo watts is equal to KVA times power factor. Kilowatt: 1000 watts. Abbreviated: kW. KILOWATT - A measure of electrical horsepower. A metric unit of power equal to approximately 1.34 horsepower. KILOWATT-HOUR - A measure of electrical energy consumption. 1000 watts being consumed per hour. Abbreviated: kWh. KINETIC ENERGY - The ability of an object to do work by virtue of its motion. (Water moving in a pipe has kinetic energy.) The energy terms that are usually used to describe the operation of a pump are "pressure" and "head". In classical mechanics, equal to one half of the body’s mass times the square of its speed. KING VALVE - Liquid receiver (refrigeration only) service valve. KIRCHOFF’S SECOND LAW - The law stating that, at each instant of time the increase of voltage around a close loop in a network is equal to the algebraic sum of the voltage drop. KNOCK - In a spark ignition engine, uneven burning of the fuel/air charge that causes violent, explosive combustion and an audible

metallic hammering noise. Knock results from premature ignition of the last part of the charge to burn. KRAFT PROCESS - A wood-pulping process in which sodium sulfate is used in the caustic soda pulp-digestion liquor. Also called Kraft pulping or sulfate pulping. kW DEMAND - The maximum rate of electric power usage required to operate a facility during a period of time, usually a month or billing period. Often called "demand". kWh CONSUMPTION - The amount of electric energy used over a period of time; the number of kWh used per month. Often called "consumption". KVA - Kilo Volt Amp

LABYRINTH SEAL - A labyrinth seal consists of a number of rings 1 - 2 millimeters thick fixed to the shaft, tapered at the outer periphery to nearly knife-sharp with a clearance to the casing of a few hundreds of a millimeter. The rings are of brass or stainless steel, the sharp edge gives better sealing and rubs off easily without excessive heating in case of a slightly eccentric shaft. Some labyrinth seals are very simple, others are complicated. LAG - A delay in the effect of a changed condition at one point in the system, on some other condition to which it is related. Also, the delay in action of the sensing element of a control, due to the time required for the sensing element to reach equilibrium with the property being controlled; i.e., temperature lag, flow lag, etc. LAMINAR FLOW - A non-turbulent flow regime in which the stream filaments glide along the pipe axially with essentially no transverse mixing. LANGELIER SATURATION INDEX - An index (SI) based upon the pH of saturation of calcium carbonate; used to determine the tendencies of a water supply toward corrosion or scaling. A positive index indicates scaling tendencies; a negative one means corrosion tendencies. (Langlier Index = pH - pHs, where pH = actual pH of water and pHs = pH at which water having the same alkalinity and calcium content is just saturated with calcium carbonate. LATENT HEAT - Change of enthalpy during a change of state, usually expressed in Btu per lb. With pure substances, latent heat is absorbed or rejected at constant pressure. LATENT HEAT - Heat energy absorbed in process of changing form of substance (melting, vaporization, fusion) without change in temperature or pressure. LATENT HEAT OF CONDENSATION - Amount of heat released (lost) by a pound of a substance to change its state from a vapor (gas) to a liquid. LATENT HEAT OF FUSION - The heat required to change 1.0 kg of a substance from the solid to the liquid state. LATENT HEAT OF VAPORIZATION - The energy required to produce saturated vapor from saturated liquid at constant pressure per unit mass of fluid.

LAW OF PARTIAL PRESSURE, DALTON’S - Each constituent of a mixture of gases behaves thermodynamically as if it alone occupied the space. The sum of the individual pressures of the constituents equals the total pressure of the mixture. LEADING EDGE - Refers to the point where the steam enters the blade of an impulse turbine. LEAK DETECTOR - Device or instrument such as a halide torch, an electronic sniffer; or soap solution used to detect leaks. LEAKAGE - In water treatment, it refers to the passing of impure steam or boiler water through the drum internals. LEAKAGE - In water treatment, the phenomenon in which some of the influent ions are not adsorbed and appear in the effluent when a solution is passed through an under regenerated exchange resin bed. LIGHT CRUDE OIL - A crude oil of relatively high API gravity (usually 40°C degrees or higher). LIGHT EMITTING DIODE - A low current and voltage light used as an indicator on load management equipment. Abbreviated: LED. LIME - A common water treatment chemical. LIME-SODA SOFTENING - A process by which the calcium and magnesium salts, constituting the harness content of a water, are chemically precipitated and removed. LINE VOLTAGE - In the control industry, the normal electric supply voltages, which are usually 120 or 240 volts. LIQUEFACTION - The change of state from a gas to a liquid. (The term liquefaction is usually used instead of condensation when referring to substances which are in a gaseous state at ordinary pressures and temperatures.) LIQUID - Substance whose molecules move freely among themselves, but do not tend to separate like those of gases. LIQUID ABSORBENT - Chemical in liquid form which has the property to "take on" or absorb other fluids. Glycol is such a liquid and widely use in the petroleum chemical industry

LIQUID IMPINGEMENT - Material removal due to action of an impingement stream of a fluid. LIQUID INDICATOR - Device located in liquid line which provides a glass window through which liquid flow may be watched. LIQUID LINE - Tube which carries liquid refrigerant from the condenser or liquid receiver to the refrigerant control mechanism. LIQUID LINE CHARGING VALVE - The line used for charging from the high side of the refrigeration system. LIQUID NITROGEN - Nitrogen in liquid form which is used as a low temperature refrigerant in expendable or chemical refrigerating systems. LIQUID PENETRANT INSPECTION - A type of nondestructive inspection that locates discontinuities that are open to the surface of a metal by first allowing a penetrating dye or fluorescent liquid to infiltrate the discontinuity, removing the excess penetrant, and then applying a developing agent that causes the penetrant to seep back out of the discontinuity and register as an indication. LIQUID RECEIVER - Cylinder (container) connected to condenser outlet for storage of liquid refrigerant in a system. LIQUID RECEIVER SERVICE VALVE - Two or three-way manual valve located at the outlet of the receiver and used for installation and service purposes. It is sometimes called the king valve. LIQUID-VAPOR VALVE REFRIGERANT CYLINDER - Dual hand valve on refrigerant cylinders, which is used to release either gas or liquid refrigerant from the cylinder. LIQUOR - Solution used in absorption refrigeration. LITHIUM BROMIDE - A chemical used in combination with water in absorption cooling systems. LOAD - The amount of heat per unit time imposed on a refrigeration system or the required rate of heat removal.

LOAD (AIR CONDITIONING) - The amount of heat per unit time imposed on a refrigeration system or the required rate of heat removal. LOAD TURBINE (GAS) - Is the turbine which is directly coupled to the load, which can only be the case with a multishaft gas turbine arrangement. LOCKED ROTOR CURRENT - See "Inrush Current". LONGITUDINAL SEAM - A riveted or welded seam along the longitudinal axis of a boiler shell or drum. LOW SIDE - The refrigerating system from the expansion point to the point where the refrigerant vapor is compressed; where the system is at or below evaporated pressure. LOW TEMPERATURE CUTOUT, REFRIGERATON - A pressure or temperature actuated device with sensing element in the evaporator, which will shut the system down at its control setting to prevent freezing chilled water or to prevent coil frosting. Direct expansion equipment may not use this device. LOW VOLTAGE - In the control industry, a power supply of 25 volts or less. LOW-SIDE FLOAT VALVE - Refrigerant control valve operated by level of liquid refrigerant in low-pressure side of system. LOW-SIDE PRESSURE - Pressure in cooling side of refrigerating cycle. LOW-SIDE PRESSURE CONTROL - Device used to keep low side evaporating pressure from dropping below certain pressure. LUBRICANT - A substance - usually petroleum based, that is used to reduce friction between two moving parts. LUBRICANT, BONDED FILM - (see lubricant, bonded solid). LUBRICANT, BONDED SOLID - A solid lubricant dispersed in a continuous matrix of a binder or attached to a surface by an adhesive material.

LUBRICANT, CHLORINATED - A lubricant containing a chlorine compound that reacts with a rubbing surface at elevated temperatures to protect it from sliding damage, (see extreme pressure lubricant). LUBRICANT, SYNTHETIC - A lubricant produced by synthesis rather than by extraction or refinement. LUBRICATION, AERODYNAMIC - (see gas lubrication). LUBRICATION, AEROSTATICS - (see pressurized gas lubrication). LUBRICATION, BATH - (see lubrication, flood). LUBRICATION, BOUNDARY - A condition of lubrication in which the friction and wear between two surfaces in relative motion are determined by the properties of the surfaces and by the properties of the lubricant other than bulk viscosity. LUBRICATION, DRIP FEED - A system of lubrication in which the lubricant is supplied to the bearing surface in the form of drops at regular intervals. LUBRICATION, DRY FILM - Lubrication that involves the application of a thin film of solid lubricant to the surface or surfaces to be lubricated. LUBRICATION, FLOOD - A system of lubrication in which the lubricant is supplied in a continuos stream at low pressure and subsequently drains away. LUBRICATION, FULL FILM - A type of lubrication wherein the solid surfaces are separated completely by an elstohydrodynamic fluid film. LUBRICATION, MAGNETO HYDRODYNAMIC Hydrodynamic lubrication in which a significant force contribution arises from electromagnetic interaction. LUBRICATION, MELT - Lubrication provided by steady melting of lubricating species. Also phase-change lubrication. LUBRICATION, MIST - Lubrication by an oil mist produced by injecting oil into a gas stream. LUBRICATION, OIL FOG - (see mist lubrication).

LUBRICATION, OIL RING - A system of lubrication for horizontal shafts. A ring of larger diameter rotates with the shaft and collects oils from a container beneath. LUBRICATION, PAD - A system of lubrication in which the lubricant is delivered to a bearing surface by a pad of felt or similar material. LUBRICATION, PRESSURIZED GAS - A system of lubrication in which a gaseous lubricant is supplied under sufficient external pressure to separate the opposing surfaces by a gas film. LUBRICATION, SOLID-FILM - Lubrication by application of a solid lubricant. LUBRICATION, SPLASH - A system of lubrication in which the lubricant is splashed onto the moving parts. LUBRICATION, THICK FILM - (also known as flood lubrication). LUBRICATION, THIN FILM - (also known as boundary lubrication). LUBRICATION, VAPOR-PHASE - A type of lubrication in which one or more gaseous reactants are supplied to the vicinity of the surface to be lubricated and which subsequently react to form a lubricious deposit on that surface. LUBRICATION, WASTE - A system of lubrication in which the lubricant is delivered to a bearing surface by cloth waste or yarn. LUBRICATION, WICK - A system of lubrication in which the lubricant is delivered to a bearing surface by means of a wick. LUBRICITY - The ability of a lubricant to reduce wear and friction, other than by its pure viscous properties.

MAGNESIUM - A scale forming element found in some boiler feed water. MAGNETIC FIELD - The region within which a body or current experiences magnetic force. MAGNETIC FLUX - The rate of flow of magnetic energy across or through a surface. MAGNETIC IRON OXIDE (Fe3O2) - Partially oxidized iron. MAGNETIC PARTICLE INSPECTION - A nondestructive method of inspection for determining the extent of surface cracks and similar imperfection in ferromagnetic materials. MAGNETIC POLE -The area on a magnetized part at which the magnetic field leaves or enters the part. It is the point of maximum attraction in a magnet. MAGNETIC REFRIGERATION - Where very low temperatures are obtained by using paramagnetic salts with magnets. MAKEUP WATER - Water fed to a system to replace that which is lost for example, water fed to a boiler to replace that lost as steam or condensate; water fed to a cooling tower to replace that lost by evaporation, drift, or other causes. MALLEABILITY - The characteristic of metals that permits plastic deformation in compression without fracture. MANGANESE - A metallic element occasionally found in very small amounts as an impurity in well-water supplies. MANIFOLD, SERVICE - Chamber equipped with gauges and manual valves, used by service technicians to service refrigerating systems. MANIFOLDING - A method of circulating the refrigerant through separate rows of tubes and mostly used with direct-expansion or dry evaporators. MANOMETER - A device to measure small to moderate pressure differentials. Device is general constructed from glass or plastic tubes filled with water, oil, alcohol or other suitable fluids.

MANOMETER - An instrument for measuring pressures: especially a Utube partially filled with a liquid, usually water, mercury, or a light oil, so constructed that the amount of displacement of the liquid indicates the pressure being exerted on the instrument. MANUAL FROST CONTROL - Manual control used to change operation of refrigerating system to produce defrosting conditions. MASS - The quantity of matter in a body as measured by the ratio of the force required to produce a given acceleration, to the acceleration. MASTER (CENTRAL) CONTROL - Control of all outlets from one point. MCM - Thousand circular mill used to describe large wire sizes. MECHANICAL SEALS - A mechanical device used to control leakage from the stuffing box of a pump. Mechanical seals are usually made of two flat surfaces, one of which rotates on a shaft. The two flat surfaces are of such tolerances as to prevent the passage of water between them. MECHANICAL WEAR - Removal of material due to mechanical process under conditions of sliding, rolling, or repeated impact. Included are abrasive wear, fatigue wear and adhesive wear, but not the corrosive and thermal wear. MELTING POINT - For a given pressure, the temperature at which the solid and liquid phases of the substance are in equilibrium. MELTING POINT - Temperature at atmospheric pressure at which a substance will melt. MEMBRANE - A barrier, usually thin, that permits the passage only of particles up to a certain size or of special nature. MEMBRANE - A thin sheet or layer. MERCAPTAN - A compound chemically similar to alcohol, with sulfur replacing the oxygen in the chemical structure. Many mercaptans have an offensive odor and are used as deodorants in natural gas. METALLURGICAL FACTOR - The condition of the metal, such as inclusions, chemical segregation’s, cold work and others, which have an impact upon the rate of electrochemical corrosion rates.

MICA - A silicate material used with high pressure gauge glasses on boilers. MICHEL THRUST BEARING MICROBAR - A unit of pressure equal to 1 dyne/cm2 (one millionth of the pressure of the atmosphere). MICRO FILTRATION - A membrane filtration process, which forces water through a porous barrier. Pores are usually between 0.1 to 20 m, when used for water purification. For filtering purposes, pore sizes are .045 m. Micron - A unit of length, the thousandth part of 1 mm of the millionth of a meter. Microprocessor - A small computer used in load management to analyze energy demand and consumption such that loads are turned on and off according to a predetermined program. MILD STEEL - A low-carbon steel of ordinary production. MILL SCALE - A natural black iron oxide coating loosely adhering to the interior of new piping or tubes. MINERAL - A naturally occurring inorganic substance having specified chemical composition and crystalline structure. MISCIBILITY - The ability of two liquids, not mutually soluble, to mix. MIX BED DEMINERALIZER - Having a mixture of cation and anion exchange resin in the same housing. MIXED PRESSURE TURBINE MIXTURE - A physical blend of two or more substances. MODULATING - Type of device or control which tends to adjust by increments (minute changes) rather than by either "full on" or "full off" operation. MODULATING CONTROL - A mode of automatic control in which the action of the final control element is proportional to the deviation, from set point, of the controlled medium.

MODULATING REFRIGERATION CYCLE - Refrigerating system of variable capacity. MODULUS OF ELASTICITY (E) - The measure of rigidity or stiffness of a material. MOISTURE INDICATOR - Instrument used to measure moisture content of a refrigerant. MOLLIER DIAGRAM - An enthalpy-entropy or enthalpy-pressure chart showing the thermodynamic properties of a fluid. MONOMER - A molecule, usually an organic compound, having the ability to join with a number of identical molecules to form a polymer. MOTOER CONTROL CENTER - A single metal enclosed assembly containing a number of motor controllers and possibly other devices such as switches and control devices. MUD DRUM - A pressure chamber of a drum or header type located at the lower extremity of a water tube boiler and fitted with blowoff valve. MULLION HEATER - Electrical heating element mounted in the mullion. Used to keep mullion from sweating or frosting. MULTIPLE STAGE COMPRESSOR - Compressor having two or more compressive steps. Discharge from each step is the intake pressure of the next in series. MULTIPLE SYSTEM - Refrigerating mechanism in which several evaporators are connected to one condensing unit. MULTI-SHAT GAS TURBINE - A gas turbine having more than one shaft, like the dual shaft arrangement. MULTISTAGE COMPRESSION REFRIGERATION SYSTEM - Where the refrigerant is vaporized and condensed alternately and is compressed in the vapor phase. MULTISTAGE THERMOSTAT - A thermostat which controls auxiliary equipment for heating or cooling in response to a greater demand for heating or cooling.

NAPHTA - A volatile, flammable liquid hydrocarbon distilled from petroleum and used as a solvent or fuel. NATURAL CIRCULATION - The circulation of a boiler caused by differences in density. Also referred as thermal or thermally induced circulation. NATURAL CONVECTION - Movement of a fluid caused only by temperature differences (density changes). NATURAL DRAFT COOLING TOWER - Cools water by moving air at low velocities. NATURAL GAS - A highly compressible, highly expandable mixture of hydrocarbons having a low specific gravity and occurring naturally in gaseous form. Besides hydrocarbon gases, natural gas may contain quantities of nitrogen, helium, carbon dioxide, hydrogen sulfide and water vapor. NATURALLY ASPIRATED - A term used to describe a diesel engine in which air flows into the engine by means of atmospheric pressure only. NC - Normally closed contacts of a relay. NEGATIVE CHARGE - The electrical potential which an atom acquires when it gains one or more electrons; a characteristic of an anion. NET POSITIVE SUCTION - The difference between total pressure and vapor pressure in a fluid flow, expressed in terms of equivalent height or "head". NEUTRAL - The circuit conductor that is normally grounded or at zero voltage difference to the ground. NEUTRALIZATION NUMBER - An ASTM number given to quenching oils that reflect the oil’s tendency toward oxidation and sludging. NEUTRALIZER - A substance that will combine with an acid or alkali chemically, thus removing the acidity or alkalinity. NEUTRALIZING AMINES - Are amines used to neutralize the acid generated by the dissolution of carbon dioxide.

NEWTON - The unit of force in the metric system. A Newton is the force required to accelerate an object of 1 kilogram mass to a velocity of 1 meter per second in 1 second. NIPPLE - A short, threaded tubular coupling, used for making connections between pipe joints. NITROGEN BLANKETING - Used with wet standby, where the space above the water level is filled with nitrogen at about 5 to 10 psig in order to keep the oxygen out. NITROGEN DIOXIDE - Mildly poisonous gas (NO2) often found in smog or automobile exhaust NO - Normally open contacts of a relay. NOBEL METAL - A chemically inactive metal, such as gold. NO-FROST FREEZER - Low-temperature refrigerator cabinet in which no frost or ice collects on freezer surfaces or materials stored in cabinet. NOISE - Any undesired sounds, usually of different frequencies, resulting in an objectionable or irritating sensation. NOMINAL SIZE - A designated size that may be different from the actual size. NOMINAL SIZE TUBING - Tubing measurement which has an inside diameter the same as iron pipe of the same stated size. NON-CARBONATED HARDNESS - Hardness in water caused by chlorides, sulfates, and nitrates of calcium and magnesium. NON-CODE INSTALLATION - Functional refrigerating system installed where there are no local, state, or national refrigeration codes in force. NON-CONDENSABLES - Gaseous material not liquefied when associated water vapor is condensed in the same environment. NON-DESTRUCTIVE INSPECTION (NDI) - A procedure such as ultrasonic or radiographic inspection, for determining the quality of a material without permanently altering anything.

NON-FERROUS ALLOY - Alloy containing less then 50 % iron. NON-FROSTING EVAPORATOR - Evaporator which never collects frost or ice on its surface. Uses only thermostatic expansion valves. NON-MECHANICAL REFRIGERATION - Those that obtain the required high and low pressure by some method other than a mechanical compressor. NON-REACTIVE SILICA - Is a polymeric form of silica; thermally unstable which reverts to normal silica when heated. Difficult to detect, but may be present when boiler feedwater shows none, but boiler water reads silica. NORMAL CARRYOVER - Refers to the carryover which occurs in any boiler operating under the best conditions. NORMAL CHARGE - Thermal element charge which is part liquid and part gas under all operating conditions. NORMALLY OPEN - (OR NORMAL CLOSED) The position of a valve, damper, relay contacts, or switch when external power or pressure is not being applied to the device. Valves and dampers usually are returned to a "normal" position by a spring. NTU - Nephelometric turbidity unit. A light -interference analytical method to measure the turbidity of water. NUCLEATE BOILING - The even boiling of water in which steam bubbles are formed within the boiler water gradually and are evenly distributed rather than being suddenly formed and erratically distributed.

OCCLUSION - An absorption process by which one solid material adheres strongly to another, sometimes occurring by co precipitation. OCTANE RATING - A classification of gasoline according to its antiknock qualities. The higher the octane number or rating, the greater are the antiknock qualities of the gasoline. OCTYL ALCOHOL - ETHYL HEXANOL - Additive in absorption machines to reduce surface tension in the absorber. OFFSET - Term used to describe the difference between the set point and the actual operating or control point. OHM - The unit of electrical resistance equal to the resistance through which a current of 1 ampere will flow when there is potential difference of one volt across it. OHM’S LAW - The relationship between current and voltage in a circuit. It states that current is proportional to voltage and inversely proportional to resistance. Expressed algebraically, in DC circuits I=E/R; in AC circuits I=E/R. OIL - A liquid of vegetable, animal, mineral, or synthetic origin that feels slippery to the touch. OIL BINDING - Condition in which an oil layer on top of refrigerant liquid may prevent if from evaporating at its normal pressure temperature. OIL GROOVE - A channel or channels in a bearing to improve oil flow through the bearing. OIL RING LUBRICATION - A system of lubrication for horizontal shafts. A ring of larger diameter rotates with the shaft and collects oils from a container below. OIL SEPARATOR - Device used to remove oil from gaseous refrigerant or steam. OIL, MINERAL - A refined hydrocarbon oil without animal or vegetable additives. OIL, MULTI-GRADE - An oil having relative little change in viscosity over a specified temperature range.

OIL, NEUTRAL - A lubricating oil obtained by distillation, not treated with acid or with alkali. OIL, TURBINE - An oil used to lubricate bearings in a steam or gas turbine. ONCE-THROUGH BOILER - A steam generating unit usually operated above the critical pressure in which there is no re-circulation of the working fluid in any part of the unit. ON-OFF CONTROL - A two position action which allows operation at either maximum or minimum condition, or on or off, depending on the position of the controller. OPEN CIRCUIT - The absence of a direct connection between two points in an electrical network. OPEN CYCLE - A gas turbine arrangement, in were the exhaust gases from the turbine are exhausted to the atmosphere without any further treatment. OPEN RE-CIRCULATING WATER SYSTEM - A system, using continuously circulated water as a heat-transfer medium, in which the water is exposed at one point to the atmosphere for either discharge or absorption of heat. OPERATING POINT - The value of the controlled condition at which the controller actually operates. Also called control point. OPERATING PRESSURE - Actual pressure at which the system works under normal conditions. This pressure may be positive or negative (vacuum). ORGANIC GROWTH - A substance resulting from the growth of biological organisms such as fungi, algae, and slime bacteria. ORGANIC MATERIAL - Contain carbon and usually hydrogen and are derived from living things. ORGANIC OXYGEN SCAVENGERS - These are organic compounds such as hydroquinone and ascorbate to remove dissolved oxygen from the boiler feedwater and condensate. ORIFICE - Accurate size opening for controlling fluid flow.

ORSAT ANALYZER - A furnace atmosphere analysis device in which gases are absorbed selectively (volumetric basis) by passing them through a series of pre-selected solvents. OSHA - Occupational Safety and Health Administration. OSMOSIS - The passage of water through permeable membrane separating two solutions of different concentration; the water passes into the more concentrated solution. OUTSIDE AIR OPENING (HVAC) - Any opening used as an entry for air from outdoors. OVER CURRENT DEVICE - A device such as a fuse or a circuit breaker designed to protect a circuit against excessive current by opening the circuit. OVERFLOW PIPE - A pipe installed at a top of a tank to enable the liquid within to be discharged to another vessel when the tank is filled to capacity. OVERLOAD - A condition of excess current; more cur rent flowing than the circuit was designed to carry. OVERRIDE - A manual or automatic action taken to by pass the normal operation of a device or system OVERSPEED TRIP - On steam turbines, a mechanism that provides absolute reliable overspeed protection by shutting off the steam supply. OXIDATION - The reaction of an element or substance with oxygen, e.g., iron is oxidized by reaction with oxygen to form rust (iron oxide). OXIDIZING AGENT - Any substance such as oxygen, or chlorine, that will readily add (take on) electrons. OXIDIZING ATMOSPHERE - A furnace atmosphere with an oversupply of oxygen that tends to oxidize materials placed in it. OXIDIZING BIOCIDE - An agent, such as chlorine, which will kill bacteria by the chemical process of oxidation.

OXYACETYLENE WELDING - An oxyfuel gas welding process in which the fuel gas is acetylene. OXYGEN CONCENTRATION CELL - (see differential aeration cell). OXYGEN CONCENTRATION CELL - The surface area in contact with the media of higher oxygen concentration becomes the cathodic area, and the area with the lower oxygen concentration becomes the anode. OXYGEN PITTING - Damage caused due to the presence of oxygen in the feedwater. Damage results are small pit-like holes in the metal. OXYGEN SCAVENGER - A substance that will absorb oxygen by chemical reaction. OZONE - Triatomic oxygen (03). Sometimes used in cold storage or air conditioning installations as an odor eliminator. Can be toxic in certain concentrations.

PACKAGE UNITS, (REFRIGERATION) - Complete refrigerating system including compressor, condenser and evaporator located in the refrigerated space. PACKED COLUMN - A tower filled with small objects, designed to obtain large surfaces per volume between rising vapors and a descending liquid. PACKING - Material made usually of woven animal, plant, mineral or metal fiber and some type of lubricant, placed in rings around the shaft of a pump and used to control leakage from the stuffing box. PACKING - The fill in a confined space in a stripping vessel, ranging from simple shaped units such as rocks or slats to complex shapes that provide large surface area per unit volume. PACKING GLAND - The metal part that compresses and holds packing in place in a stuffing box. PARALLEL CIRCUIT - One where all the elements are connected across the voltage source. Therefore, the voltage on each element is the same but the current through each may be different. PARSON TURBINE PARTIAL PRESSURES - Condition where two or more gases occupy a space and each one creates part of the total pressure. PASCAL - The accepted metric unit of measurement or pressure and stress component in the measurement of viscosity. A Pascal is equal to a force of 1 Newton acting an area of 1 square meter. The symbol is Pa. PASCAL'S LAW - Pressure imposed upon a fluid is transmitted equally in all directions. PASSIVATING (ANODIC) INHIBITORS - A material capable of forming a protective oxide film on metal surfaces. PASSIVATION - The process of rendering a metal surface chemically inactive, either by electrochemical polarization or by contact with a passivating agent.

PASSIVATOR - A type of corrosion inhibitor that appreciably changes the potential of a metal to a more noble (positive) value. PASSIVATOR - A type of corrosion inhibitor that appreciably changes the potential of a metal to a more positive value. PASSIVE-ACTIVE CELL - A corrosion cell in which the anode is a metal in that active state and the cathode is the same metal in the passive state. PASSIVITY - A condition on metal surfaces that inhibits electrochemical action between the metal and its environment, such as with boiler water. PATHOGENIC BACTERIA - Disease-causing bacteria. PEAK DEMAND - The greatest amount of kilowatts needed during a demand interval. PEAK LOAD PRICING - A pricing principle that charges more for purchases that contribute to the peak demand and, thereby, cause the expansion of productive capacity when the peak demand exceeds the peak capacity (less minimum excess capacity). In the electric power industry, this means charging more hr electricity bought on or near the seasonal peak of the utility or on or near the daily peak of the utility. The latter requires special meters; the former does not. PEAKING LOAD - Is the electrical load drawn on the system during high power usage. Usually on very hot or cold days or during the supper hour. PELTIER EFFECT - When direct current is passed through two adjacent metals one junction will become cooler and the other will become warmer. This principle is the basis of thermoelectric refrigeration. PERFECT GAS - A hypothetical gas obeying the relation pv = RT. PERMANENT GASES - Cryogenic refrigerants. PERMEABILITY - The ability of a body to pass fluid under pressure. PETROGRAPHIC STUDY OF BOILER SCALES The systematic and descriptive study of rocks. This method also allows the identification of boiler scales, since scale can consist of a large variety of minerals

PETROLEUM OIL - (see mineral oils). pH - The negative logarithm of the hydrogen-ion concentration of a solution; simply a measure of the relative acidity or alkalinity of a water solution. (pH 1 very acidic; pH 14, very basic; pH 7, neutral). pH OF SATURATION (pHs) - The pH at which a sample of water is saturated with a specific salt; for example, the pH of saturation of calcium carbonate is the pH of a saturated solution of calcium carbonate. PHASE - Part of an AC voltage cycle. Residential electrical service is 2phase; commercial facilities are usually 3-phase AC voltage. PHIAL -Term sometimes used to denote the sensing element on a thermostatic expansion valve. PHOSPHATE - An ion, compound, or salt containing phosphorus and oxygen, such as sodium phosphate (Na3P04). PHOSPHATE TREATMENT - An internal boiler water treatment method to reduce calcium in the boiler with low hardness feedwater. PHYSICAL STABILITY - The quality which an ion-exchange resin must possess to resist changes that might be caused by attrition, high temperatures, and other physical conditions. PHYSICAL WATER TREATMENT - Refers to the treatment of removing dissolved gases from the boiler feedwater, using steam. PIG IRON - High-carbon iron made by reduction of iron ore in the blast furnace. PILOT DUTY RELAY - A relay used for switching loads such as another relay or solenoid valve coils. The pilot duty relay contacts are located in a second control circuit. Pilot duty relays are rated in volt-amperes (VA). PILOT OIL PRESSURE PIPE SCALE - Rust or mill scale found on the interior of water pipe. PIT - Corrosion localized in a small spot.

PITOTE TUBE - An open ended tube arrangement to face against the current of a stream of fluid; used in measuring the velocity head of a flowing medium. PITS - Petroleum Industry Training Service. (Canada) PITTING - Localized corrosion of a metal characterized by small blisters under which holes have perforated the metal. PLASTIC DEFORMATION PLASTICITY - The ability of a substance to be deformed without rupturing. PLENUM CHAMBeR - An air compartment connected to one or more distributing ducts. PLENUM CHAMBER - Chamber or container for moving air or other gas under a slight positive pressure. PNEUMATIC - Operated by air pressure. PNEUMATIC-ELECTRIC (PE) SWITCHES - Device that operates an electric switch from a change of air pressure. pOH - An expression of the alkalinity of a solution; the negative logarithm of the hydroxyl-ion concentration. POINT, CRITICAL - Of a substance, state point at which liquid and vapor have identical properties; critical temperature, critical pressure, and critical volume are the terms given to the temperature, pressure, and volume at the critical point. Above the critical temperature or POLARITY - The direction of current flow in a DC circuit. By convention, current flows from plus to minus. Electron flow is actually in the opposite direction. POLARIZE - In corrosion, to develop a barrier on the anodic or cathodic surface, disrupting the corrosion process. POLE - An electrical connection point. In a panel, the point of connection. On a device, the terminal that connects to the power.

POLYELECTROLYTE - A water-soluble polymer that is highly charged with cationic or anionic sites. Used as an aid with coagulants. POLYMER - A chemical compound formed by the adjoining of many molecules of the same characteristics; for example, polyvinyl chloride is a polymer of the molecule vinyl chloride. POLYMERIC DISPERSANT - A water-soluble polymer that acts as a suspending agent; that is, it promotes suspension of particles in water so that they resist settling. POLYPHOSPHATE - A chemical compound formed by the adjoining of phosphate ions, hence a polymer of phosphate. POLYTROPHIC PROCESS - A non-adiabatic reversible process characterized by the equation of path, pv = constant. POROUS VASE - A vase having a porous construction, which was used to cool its content. POSITIVE CHARGE - The electrical potential acquired by an atom which has lost one or more electrons; a characteristic of a cation. POTENTIAL ENERGY - The energy, that a body has by virtue of its position or state, enabling it to do work. (Water in a reservoir has potential energy by virtue of its elevation above some other point.) POTENTIAL TRANSFORMER - A voltage transformer. The voltage supplied to a primary coil induces a voltage in a secondary coil according, to the ratio of the wire windings in each of the coils. POTENTIOMETER - An electromechanical device having a terminal connected to each and to the resistive element, and a third terminal connected to the wiper contact. The electrical input is divided as the contact moves over the element, thus making it possible to mechanically change the resistance. POUR POINT - The lowest temperature at which a lubricant can be observed to flow under specified conditions. For oil, the pour point is a temperature -15°C above the temperature at which the oil is solid. POUR-POINT DEPRESSANT - An additive that lowers the pour point of a lubricant.

POWER (P) - Expressed in watts (W) or kilowatts (kW), and is equal to: POWER ELEMENT - Sensitive element of a temperature-operated control. POWER FACTOR (pf) - A quantity that relates the volt amperes of an AC circuit to the wattage (power = volt-amperes x power factor). Power factor also is the ratio of the circuit resistance (R) to the impedance (Z) expressed as a decimal between zero and one (pf = R/Z). When the power factor equals one, all consumed power produces useful work. POWER FACTOR CHARGE - A utility charge for "poor" power factor. It is more expensive to provide power to a facility with a poor power factor (usually less than 0.8). POWER FACTOR CORRECTION - Installing capacitors on the utility service’s supply line to improve the power factor of the building. ppb - equals 0.001 ppm. (Parts per billion) PRECIPITATE - An insoluble reaction product; in an aqueous chemical reaction, usually a crystalline compound that grows in size to become settable. PRECIPITATING (CATHODIC) INHIBITORS - The are chemicals which form insoluble precipitates that are able to coat and protect surfaces. They are less durable then the passivating type inhibitors. PRECIPITATION - A process whereby salts drop or come out of a water solution. PRECISION PHOSPHATE TREATMENT - A phosphate treatment based upon maintaining 2 to 4 ppm of phosphate and 15 to 50 ppm of hydrate alkalinity in the boiler. PREDICTING METHOD - A method for determining when load shedding should occur. A formula is used to arrive at a preset kilowatt limit. Then the actual amount of energy accumulated during the utility's demand intervals is measured. A projection is made of the actual rate of energy usage during the rest of the interval. If the predicted value exceeds the preset limit, loads will be shed.

PREIGNITION - A condition in an internal combustion engine characterized by a knocking sound and caused by the fuel-air mixture having been ignited to soon because of an abnormal condition. PRESSURE - The normal force exerted by a homogeneous liquid or gas, per unit of area, on the wall of its container. PRESSURE COMPOUNDING PRESSURE DROP - Pressure loss in fluid pressure, as from one end of a duct or pipe to the other, due to friction, dynamic losses, and changes in velocity pressure. PRESSURE GAUGE - Instrument for measuring the pressure exerted by the contents on its container. PRESSURE HEAD - The height to which liquid can be raised by a given pressure (sometimes referred to as pump head). PRESSURE MOTOR CONTROL - Device which opens and closes an electrical circuit as pressures change. PRESSURE OPERATED THERMOMETER - Temperature indicator which is controlled by bellows, a capillary or remote sensitive bulb. PRESSURE REGULATOR, SUCTION (REFRIGERATION COMPRESSORS) An automatic valve designed to limit the suction pressure to prevent motor overload. PRESSURE SWITCH - Switch operated by a rise or drop in pressure. PRESSURE VELOCITY - In moving fluid, the pressure capable of causing an equivalent velocity, if applied to move the same fluid through an orifice such that all pressure energy expended is converted into kinetic energy. PRESSURE, ABSOLUTE - Pressure referred to that of a perfect vacuum. It is the sum of gauge pressure and atmospheric pressure. PRESSURE, ATMOSPHERIC - It is the pressure indicated by a barometer. Standard atmosphere is the pressure equivalent

PRESSURE, CRITICAL - Vapor pressure corresponding to the substance's critical state at which the liquid and vapor have identical properties. PRESSURE, GAGE - Gauge: Pressure above atmospheric. PRESSURE, HYDROSTATIC - The normal force per unit area that would be exerted by a moving fluid on an infinitesimally small body immersed in it if the body were carried along with the fluid. PRESSURE, OPERATING - Pressure at which a system is operating. PRESSURE, PARTIAL - Portion of total gas pressure of a mixture attributable to one component. PRESSURE, SATURATION- The saturation pressure for a pure substance for any given temperature is that pressure at which vapor and liquid, or vapor and solid, can coexist in stable equilibrium. PRESSURE, STATIC - The normal force per unit area that would be exerted by a moving fluid on a small body immersed in it if the body were carried along with the fluid. Practically, it is the normal force per unit are at a small hole in a wall of the duct through which the fluid flows (piezometer) or on the surface of a stationary tube at a point where the disturbances, created by inserting the tube, cancel. It is supposed that the thermodynamic properties of a moving fluid depend on static pressure in exactly the same manner as those of the same fluid at rest depend upon its uniform hydrostatic pressure PRESSURE, TOTAL - In the theory of the flow of fluids, the sum of the static pressure and the velocity pressure at the point of measurement. Also called dynamic pressure. PRESSURE, VAPOR - The partial pressure exerted by the water vapor contained in air. PRESSURE-HEAT DIAGRAM - Graph of refrigerant pressure, heat and temperature properties. (Mollier's diagram.) PRESSURESTAT - A control which reacts to pressure changes in the evaporator. PRESSURE-VELOCITY COMPOUNDING -

PRETREATMENT - Also referred to as external treatment, consisting of treating the raw make-up water, and include removing dissolved oxygen, carbon dioxide, suspended solids, hardness, alkalinity, silica, dissolved solids, etc.. PRIMARY AIR - The initial air stream discharged by an air outlet (the air being supplied by a fan or supply duct) prior to any entrainment of the ambient air or for he purpose of combustion. PRIMARY CONSTITUENTS - Refers to the category of dissolved solids present in water at a level of more then 5 mg/L. PRIMARY CONTROL - A device which directly or indirectly controls the control agent in response to needs indicated by the controller. Typically a motor, valve, relay, etc. PRIMARY ELEMENT - The portion of the controller which first uses energy derived from the controlled medium to produce a condition representing the value of the controlled variable; for example, a thermostat bimetal. PRIMARY SYSTEM - A closed water system in which the water is circulated directly through a chiller for cooling or heat exchanger or boiler for heating. PRIME MOVER - An engine or other device by which natural source of energy is converted into mechanical energy. PRIMING - The phenomenon in which the level of water in a boiler is changed by bouncing rapidly. The result is, that boiler water will enter the steam flow. PROCESS HOT WATER - Hot water needed for manufacturing processes over and above the "domestic hot water" that is for the personal use of industrial workers. PROPANE - A paraffin hydrocarbon (C3H8) that is a gas at ordinary atmospheric conditions but easily liquefied under pressure. PROPORTIONAL BAND - The range of values of a proportional positioning controller through which the controlled variable must pass to move the final control element through its full operating range. Commonly used equivalents are "throttling range" and "modulating range".

PSI - Symbol or initials used to indicate pressure measured in pounds per square inch. PSIA - Symbol or initials used to indicate pressure measured in pounds per square inch absolute. Absolute pressure equals gauge pressure plus atmospheric pressure. The "A" indicates that the gauge pressure is reading in absolute. PSIG - Symbol or initials used to indicate pressure in pounds per square inch gauge. The "G" indicates that is gauge pressure and not absolute pressure. PSYCHROMETER - An instrument for ascertaining the humidity or hygrometric state of the atmosphere. PSYCHROMETER OR WET BULB HYGROMETER – An instrument for measuring the relative humidity of atmospheric air. PSYCHROMETRIC CHART – A chart that shows relationship between the temperature, pressure and moisture content of the air. PSYCHROMETRIC MEASUREMENT - Measurement of temperature pressure and humidity using a psychometric chart. PSYCHROMETRY - The study of air-vapor mixtures. PULL DOWN - An expression indicating action of removing refrigerant from all or part of a refrigeration system. PULSATION DAMPENER - Any gas or liquid charged, chambered device that minimizes periodic increases and decreases in pressure. PULSE-ECHO TECHNIQUES - Corrosion detecting processes which, by recording the action of ultrasonic waves artificially introduced into production structures, can determine metal thickness and detect flaws. PUMP - A device that increases the pressure on a fluid or raises it to a higher level. PUMP DOWN - The act of using a compressor or a pump to reduce the pressure in a container or a system.

PUMP, POSITIVE DISPLACEMENT - A pump that moves a measured quantity of fluid with each stroke of a piston or each revolution of vanes or gears. PUMP, ROTARY - A pump that moves fluid by positive displacement, using a system of rotating vanes, gears, or lobes. PUMP-DISCHARGE PRESSURE - The point of highest pressure in a recirculating water system which is at the discharge side of the recirculating pump. PURGING - Releasing compressed gas to atmosphere through some part or parts for the purpose of removing contaminants from that part or parts. PURGING VALVES - Devices used to remove non-condensable gases from the refrigeration system. PYROMETER - A device for measuring temperatures above the range of liquid thermometers.

QUALITY - Weight fraction of the vapor in a vapor-liquid mixture. QUICKLIME - Unslaked lime (calcium oxide).

RACEWAY - Any support system, open or closed, for carrying electric wires. RADIAL THRUST RADIANT HEATING - Heating system in which warm or hot surfaces are used to radiate heat into the space to be conditioned. RADIATION - Transfer of heat by electromagnetic waves. RADIATION LOSSES (STEAM TURBINE) RAM AIR - Air forced through the condenser due to the rapid movement of steam from the turbine exit. RANKINE SCALE - Name given the absolute (Fahrenheit) scale. Zero (0) R on this scale is -460°F. RANKINE TEMPERATURE - Degrees Fahrenheit plus 491.60. RAPTURE MEMBRANE - A metal membrane (pressure relief device) designed to rapture at a predetermined pressure. RAW MAKEUP WATER - Untreated water fed to a system to replace that lost. RAW WATER - With water treatment it means untreated feedwater or water in its natural state, prior to any treatment. REACTION PRINCIPLE REAGENT - A substance, chemical, or solution used in laboratory to detect, measure, or react with other substances, chemicals or solutions. RE-CARBONATION - A process using carbon dioxide gas to stabilize and thereby prevent precipitation of calcium carbonate from cold process lime or lime-soda softened water. RECEIVER - An auxiliary storage receptacle for fluids. RECEIVER DEHYDRATOR - Small tank which serves as liquid refrigerants reservoir and which also contains a desiccant so remove moisture. Used on most automobile air conditioning installations.

RECEIVER HEATING ELEMENT - Electrical resistance mounted in or around liquid receiver. It is used to maintain head pressures when ambient temperature is low. RECEIVER-DRIER - Cylinder (container) in a refrigerating system for storing liquid refrigerant and which also holds a quantity of desiccant. RECIPROCAL - A format defined by 1 divided by the complex number. RECIPROCATING COMPRESSOR - Compressor which uses a piston and cylinder mechanism to provide pumping action. RECORDING THERMOMETER - Temperature measuring instrument which has a pen marking a moving chart. RECTIFIER - A device used to convert AC current into DC current. RECUPERATOR - Equipment for transferring heat from gaseous products of combustion to incoming air or fuel. The incoming material passes through pipes surrounded by a chamber through which the outgoing gases pass. RED WATER - Water that has a red, cloudy appearance caused by suspended red iron oxide. REDOX POTENTIAL - A process designed to determine if a corrosion process will occur. REDUCING ELBOW - A fitting that makes an angle between two joints of pipe and that decreases in diameter from one end to the other. REDUCING FLANGE - A flange fitting used to join pipes of different diameters. REDUCING NIPPLE - A pipe fitting that is threaded on both ends and decreases in diameter from one end to the other. REDUCING TEE - A "T"shaped pipe fitting with openings of two different sizes. The relationship: REDUCTION - Reduction is the addition of hydrogen, removal of oxygen, or the addition of electrons to an element or compound. REED VALVE - Thin, flat, tempered steel plate fastened at one end.

REFRIGERANT - The fluid used for heat transfer in a refrigerating system, which absorbs heat at a low temperature and a low pressure of the fluid and rejects heat at a higher temperature and a higher pressure of the fluid, usually involving changes of state of the fluid. REFRIGERANT - The working fluid used in refrigerators. REFRIGERANT CHARGE - Quantity of refrigerant in a system. REFRIGERANT CONTROL - Device which meters flow of refrigerant between two areas of a refrigerating system. It also maintains pressure difference between high-pressure and low-pressure side of the mechanical refrigerating system while unit is running. REFRIGERATING CAPACITY - The ability of a system to remove heat as compared with the cooling effect produced by melting of ice. REFRIGERATING EFFECT - The amount of heat transferred by one kg of refrigerant as it circulates in the refrigeration system. REFRIGERATION - Controlled transfer of heat from a lower temperature to a higher temperature region. REFRIGERATION OIL - Specially prepared oil used in refrigerator mechanism which circulates, to some extent, with refrigerant. REFRIGERATOR - A device to transfer heat from a low temperature to a high temperature medium. REGENERATE - The solution used to restore the activity of an ion exchanger. Acids are employed to restore a cat ion exchanger to its hydrogen form; brine solutions may be used to convert the cat ion exchange to the sodium form. The anion exchanger may be rejuvenated by treatment with an alkaline solution. REGENERATION - Restoration of the activity of an ion exchanger by replacing the ions adsorbed from the treated solution by ions that were adsorbed initially on the resin. REGENERATIVE CYCLE - Is a gas turbine cycle employing a heat exchanger to recover some of the heat before discharging the gases from the gas turbine to the atmosphere, to recover some of the from

REGENERATIVE GAS TURBINE - Referring to a gas turbine employing heat exchanger between the compressor and the combustor for the purpose of recovering heat. REGENERATOR Register: A grille equipped with an integral damper or control valve. REJUVENATION - (see regeneration) RELATIVE HUMIDITY - The amount of moisture the air holds relative to the maximum moisture the air can hold at the same temperature. Relative Humidity (RH): The ratio of water vapor in the air as compared to the maximum amount of water vapor that may be contained. RELATIVE HUMIDITY -The ratio, expressed as a percentage, of the amount of water vapor present in a given volume of air at a given temperature to the amount required to saturate the air at that temperature. RELAY - An electromechanical switch that opens or closes contacts in response to some controlled action. Relay contacts can be normally open (NO) and/ or normally closed (NC). Relays may be electric, pneumatic, or a combination of both. RELAY, THERMAL - A switching relay in which a small heater warms a bimetal element which bends to provide the switching force. RELIEF VALVE - Safety device on a sealed system. It opens to release fluids before dangerous pressure is reached. Also called pressure relief valve. REMOTE SYSTEM - Refrigerating system in which condensing unit is away from space to be cooled. Remote Temperature Set Point: Ability to set a temperature control point for a space from outside the space. Often used in public areas. RESET - A process of automatically adjusting the control point of a given controller to compensate for changes in outdoor temperature. The hot deck control point is normally reset upward as the outdoor

temperature drops. The cold deck control point is normally reset downward as the outdoor temperature increases. RESET RATIO - The ratio of change in outdoor temperature to the change in control point temperature. For example, a 2:1 reset ratio means that the control point will increase 1 degree for every 2 degrees change in outdoor temperature. RESIDUAL - Means small amount of, like oxygen, sulfite, acid., etc.. RESISTANCE - The opposition which limits the amount of current that can be produced by an applied voltage in an electrical circuit, measured in ohms. RESISTANCE, THERMAL - The reciprocal of thermal conductance. RESISTIVE LOADS - Electrical loads whose power factor is one. Usually contain heating elements. RESONANT VIBRATION - Everything has a natural frequency. This frequency is effected by two properties: Mass and Stiffness. This "natural frequency" is the cause of many vibration problems in HVAC equipment. If you strike an object (say a tuning fork or a bell) it will continue to vibrate at its natural frequency until damping extinguishes the vibration. RESTRICTOR - A device for producing a deliberate pressure drop or resistance in a line by reducing the cross-sectional flow area. Return Air: Air returned from conditioned or refrigerated space. RETURN-STEAM CONDENSATE - That steam produced by a boiler which returns to the boiler after it has condensed. REVERSE CYCLE DEFROST - Method of heating evaporator for defrosting. Valves move hot gas from compressor into evaporator. REVERSE CYCLE REFRIGERATION - A refrigeration system which uses reject heat to produce warmth. REVERSE DEIONIZATION - The use of an anion-exchange unit and a cation-exchange unit-in that order-to remove all ions from solution.

REVERSE OSMOSIS - A process that reverses (by the application of pressure) the flow of water in the natural process of osmosis so that it passes from the more concentrated to the more dilute solution. REVERSIBLE PROCESS - A process by which a fluid is made to undergo a change of state and by traversing the path in exactly the reverse of the original path is returned to its original state, and all associated systems are similarly returned to their original state. REVERSING VALVE - Device used to reverse direction of the refrigerant flow depending upon whether heating or cooling is desired. RING LUBRICATED SLEEVE BEARING RINSE - The operation which follows regeneration; a flushing out of excess regenerate solution. ROTARY COMPRESSOR - Mechanism which pumps fluid by using rotating motion. RUNNING CURRENT - The current that flows through a load after inrush current. Usually called "full load current". RUNNING TIME - Amount of time a condensing unit is run per hour or per 24 hours. RUST - A visible corrosion product consisting of hydrated oxides of iron. Applied only to ferrous alloys. RYZNAR STABILITY INDEX - An index based on calcium carbonate pH of saturation vs. actual pH to determine scaling or corrosion tendencies of a water (R.I. = 2 pHs).

SACRIFICIAL ANODES - Coupling of a more active metal to a structure resulting in a galvanic current flow through the corroding electrolyte. SACRIFICIAL PROTECTION - Reduction of corrosion of a metal in an electrolyte by galvanically coupling it to a more anodic metal. A form of cathode protection. SADDLE VALVE (TAP-A-LINE) - Valve body shaped so it may be silver brazed or clamped onto a refrigerant tubing surface. SADDLE VALVE (TAP-A-LINE) - Valve body shaped so it may be silver brazed or clamped onto a refrigerant tubing surface. SAFETY CAN - Approved container of not more than 5 gallon capacity. It has a spring closing lid and spout cover. It is designed to relieve internal pressure safely when exposed to fire. SAFETY CONTROL - Device to stop refrigerating unit if unsafe pressure and/or temperatures and/or dangerous conditions are reached. SAFETY PLUG - Device which will release the contents of a container before rupture pressures are reached. SALINITY - A measure of the concentration of dissolved mineral substances in water. SALT SPITTING - The ability of an anion exchanger to convert a salt solution to caustic; the ability of a cation exchanger to convert a salt solution to acid. SATURATED AIR - When the air cannot hold any more moisture. SATURATED LIQUID - A liquid which is at saturation pressure and saturation temperature; in other words, a liquid which is at its boiling point for any given pressure. SATURATED VAPOR - A vapor which is at saturation pressure and saturation temperature. A saturated vapor cannot be superheated as long as it is in contact with the liquid from which it is being generated. SATURATION - Condition existing when substance contains all of another substance it can hold for that temperature and pressure.

SATURATION INDEX - The relation of calcium carbonate to the pH, alkalinity, and hardness of a water to determine its scale forming tendency. SATURATION PRESSURE - The point, where at a given temperature a pure substance starts to boil. SATURATION TEMPERATURE - The point, where at a given pressure a pure substance starts to boil. SAYBOLT UNIVERSAL VISCOSITY - A commercial measure of viscosity expressed as a time in seconds required for 60 mL of a fluid to flow through the orifice of the standard Saybolt universal viscometer at a given temperature under specific conditions; used for the lighter petroleum products and lubrication oils. SCALE - Surface oxidation, consisting of partially adherent layers of corrosion products, left on metals by heating or casting in air or in other oxidizing atmosphere. Also a deposit on a heat-transfer surface resulting from precipitation of salts present in water in contact with that surface, forming a hard, dense material. SCALE CAUSING ELEMENTS - Calcium and magnesium elements forming scale. SCALE REMOVAL - Waterside, removal of scale using either the mechanical, the water treatment or the acid cleaning process. SCC - Stress corrosion cracking. SCREENS - Equipment designed to prevent larger objects to enter water treatment system. SCREW PUMP - Compressor constructed of two mated revolving screws. SCRUBBER - An apparatus for the removal of solids from gases by entrainment in water. SEAL, MAGNETIC - A seal that uses magnetic material, instead of springs or bellows, to provide the closing force. SEAL, ROTARY - A mechanical seal that rotates with a shaft and is used with a stationary mating ring.

SECOND LAW OF THERMODYNAMICS - Heat will flow only from material at higher temperature to material at lower temperature. SECONDARY REFRIGERANT - Chilled liquid-like water, which is circulated to distance units where air is to be cooled in individual rooms. SECONDARY SYSTEM - A re-circulating water system that is a takeoff from a primary system; it does not circulate directly through the source of heat or cooling but only indirectly through a heat exchanger. SECONDARY TREATMENT - Treatment of boiler feedwater or internal treatment of boiler water after primary treatment. SEDIMENTATION - Gravitational settling of solid particles in a liquid system. SEEBECK EFFECT - When two different adjacent metals are heated, an electric current is generated between the metals. SENSIBLE HEAT - Heat which causes a change in temperature of a substance. SENSIBLE HEAT - Sensible heat is any heat transfer that causes a change in temperature. Heating and cooling of air and water that may be measured with a thermometer is sensible heat. Heating or cooling coils that simply increase or decrease the air temperature without a change in moisture content are examples of sensible heat. SENSIBLE HEAT FACTOR - The ratio of sensible heat to total heat. SENSING DEVICE - A device that keeps track of the measured condition and its fluctuations so that when sufficient variation occurs it will originate the signal to revise the operation of the system and offset the change. Example: a thermostat "bulb". A sensing de vice may be an integral part of a controller. SENSING ELEMENT - The first system element or group of elements. The sensing element performs the initial measurement operation. SEPARATOR - A tank type pressure vessel installed in a steam pipe to collect condensate to be trapped off and thus providing comparatively dry steam to the connected machinery.

SEPARATOR - Device to separate one substance from another. SEQUENCER - A mechanical or electrical device that may be set to initiate a series of events and to make the events follow in sequence. SEQUESTER - To form a stable, water-soluble complex. SEQUESTRANT - A substance that holds a mineral or metal in solution beyond its saturation point. SERIES CIRCUIT - One with all the elements connected end to end. The current is the same throughout but the voltage can be different across each element. SERVICE DROP - The overhead service wires that serve a building. SERVICE SWITCH - Disconnect switches or circuit breakers. Purpose is to completely disconnect the building from the electric service. SERVICE VALVE - Manually operated valve mounted on refrigerating systems used for service operation. SET POINT - The value of the controlled condition at which the instrument is set to operate. SETTLING BASIN - A containment design with external water treatment to settle sediments and to clarify. SHAFT SEAL - Device used to prevent leakage between shaft and housing. SHARP FREEZING - Refrigeration at temperatures slightly below freezing, with moderate air circulation. SHEAR PIN COUPLING SHED - To de-energize a load in order to maintain a kW demand set point. SHED MODE - A method of demand control that reduces kW demand through shedding and restoring loads. SHELL AND TUBE FLOODED EVAPORATOR - Device which flows water through tubes built into cylindrical evaporator or vice versa.

SHELL TYPE CONDENSER - Cylinder or receiver which contains condensing water coils or tubes. SHELL-AND-TUBE - Designation of a heat exchanger having straight tubes encased inside a shell. SHIELDED CABLE - Special cable used with equipment that generates a low voltage output. Used to minimize the effects of frequency "noise" on the output signal. SHOCK DOSAGE - The feeding of treatment to a system all in one slug or dose rather than gradually (also called a slug dosage). SHOCK FEEDER - A device which is used to add treatment to a system in an instantaneous manner. SHORT CIRCUIT - A direct connection of low resistive value that can significant alter the behavior of an element or system. SHORT CYCLING - Unit runs and then stops at short intervals; generally this excessive cycling rate is hard on the system equipment. SHROUD, TURBINES - Also referred to as the sealing strip on turbine blades. Its purpose is to supply rigidity to the blades, lessen vibration and provide sealing between stages. SHROUD, PUMPS - The front and/or back of an impeller. SHUNT - A device to divert part of an electric current. SIGHT GLASS - Glass tube or glass window in refrigerating mechanism. It shows amount of refrigerant or oil in system and indicates presence of gas bubbles in liquid line. SILICA - Silicon dioxide (Si02), a mineral found naturally as quartz or in complex combination with other elements such as silicates. SILICA GEL - Absorbent chemical compound used as a drier. When heated, moisture is released and compound may be reused. SILICA, COLLOIDAL - Silica in colloidal form. SILICA, VOLATILE - Silica carryover with steam.

SILT DENSITY INDEX - A measure of the tendency of a water to foul a reverse osmosis membrane, based on time flow through a membrane filter at constant pressure. SIMPLE CYCLE - Referring to the gas turbine cycle consisting only of compression, combustion and expansion. SINGLE PHASING - The condition when one phase of a multiphase (poly-phase) motor circuit is broken or opened. Motors running when this occurs may continue to run but with lower power output and over heating. SINGLE SHAFT GAS TURBINE - A gas turbine arrangement in which the compressor and the gas turbine are all coupled to one shaft. SINGLE STAGE COMPRESSOR - Compressor having only one compressive step between inlet and outlet. SKIN CONDENSER - Condenser using the outer surface of the cabinet as the heat radiating medium. SLIME - A soft, sticky, mucus-like substance, originating from a bacterial growth. SLING PSYCHROMETER - Measuring device with wet and dry bulb thermometers. Moved rapidly through air it measures humidity. SLUDGE - A deposit on a heat-transfer surface that does not have the hard, crystalline structure of a scale but is softer and less dense. SLUG - A unit of measure for mass in the English system, which equals 14.6 kg in the SI system. SLUGGING - Condition in which mass of liquid enters compressor causing hammering. SLURRY - A water containing high concentration of suspended solids, usually over 5000 mg/L. SLURRY EROSION - Material removal due to the combined action of corrosion and wear. SODA ASH - A common water treatment chemical, sodium carbonate.

SODIUM CHLORIDE - Common table salt, used to produce a brine solution, used a secondary refrigerant. SODIUM SULFITE (Na2S03) - A chemical used with water treatment to remove small amounts of oxygen. SODIUM TRACER METHOD - A technique used to measure dissolved solids in steam to values as low as 0.001 ppm. SODIUM ZEOLITE SOFTENING - The process of removing scale forming ions of calcium and magnesium and replacing them with the equivalent amount of sodium ions. SOFT WATER - Water that is free of magnesium or calcium salts. SOFTENING - The removal of hardness (calcium and magnesium) from water. SOLAR HEAT - Heat created by visible and invisible energy waves from the sun. SOLENOID VALVE - Electromagnet with a moving core. It serves as a valve or operates a valve. SOLID ABSORBENT REFRIGERATION - Refrigeration system which uses solid substance as absorber of the refrigerant during the cooling part of the cycle and releases refrigerant when heated during generating part of cycle. SOLID STATE HALOGEN LEAK DETECTOR - An electronic leak detector for all halogen. related refrigerants. SOLUBLE IRON - Usually present in cooling water systems and can arise from metallurgical corrosion. SOLU-BRIDGE - An electronic instrument used to measure conductivity of a water sample to determine the dissolved solids content. SOUR GAS - A gaseous environment containing hydrogen sulfide and carbon dioxide in hydrocarbon reservoirs. SOUR WATER - Waste water containing malodorous materials, usually sulfur compounds.

SPARGER - An extension into the bottom of a tank of a pipe which has a distribution nozzle on the end for mixing one fluid with another. SPECIFIC CONDUCTANCE - Measures the ability of a water to conduct electricity. Conductivity increases with total dissolved solids and is therefore used to estimate dissolved solids present in the water. SPECIFIC GRAVITY - The density of a substance compared to the density of a standard material such as water. SPECIFIC HEAT - Ratio of quantity of heat required to raise temperature of a body 1 degree to that required to raise temperature of equal mass of water 1 degree. SPECIFIC HEAT (Cp) - The ratio of the mount of heat required to raise a mass of material 1 degree in temperature to the amount required to raise equal mass of reference substance, usually water, 1 degree in temperature. SPECIFIC HUMIDITY - Ratio of weight of vapor to the weight of gas in a unit volume of an air-water vapor mixture. SPECIFIC VOLUME - Volume per unit mass of a substance. SPEED GOVERNING SPLASH SYSTEM, OILING - Method of lubricating moving parts by agitating or splashing oil in the crankcase. SPLIT-STREAM DEALKALIZER - Where the flow of water is divided through a parallel arrangement of hydrogen and sodium cat ion exchanger. The combined product being soft and low in alkalinity. SPRAY CARRYOVER - Are referred to a mist or fog and are a degree of atomization of the boiler water and carried with the steam. This type of carryover is to be prevented by the drum internals. SPRAY COOLING - Method of refrigerating by spraying expendable refrigerant or by spraying refrigerated water. SPRAY MANIFOLD - A pipe, or extension of a water line, that has several openings fitted with nozzles which spray water.

SPRAY-COIL UNIT - A cooling circuit that sprays water over cooling coils through inflowing air to humidify or dehumidify that air, as required. SPRAY-COOLING CIRCUIT - An open cooling-water circuit which sprays water and cools by evaporation, for example, a cooling tower, all evaporative condenser, an air washer, or a spray-coil unit. Spread: The divergence of the air stream in a horizontal or vertical plane after it leaves the outlet. STABILITY INDEX - An imperical modification of the saturation index used to predict scaling or corrosive tendencies in water systems. STAINLESS STEEL STANDARD AIR CONDITIONS - Standard air density has been set at 0.075 Ib/cu ft. This corresponds approximately to dry air at 70°F and 29.92 in Hg. In metric units, the standard air density is 1.2041 kg/m3 at 20°C and at 101.325 kPa. STANDARD CONDITIONS - The standard conditions referred to in environmental system work for air are: dry air at 70°F and at an atmospheric pressure of 29.92 inches mercury (in Hg). For water, standard conditions are 68°F at the same barometric pressure. At these standard conditions, the density of air is 0.075 pounds per cubic feet and the density of water is 62.4 pounds per cubic foot. STATE - Refers to the form of a fluid, either liquid, gas or solid. Liquids used in environmental systems are water, thermal fluids such as ethylene glycol solutions, and refrigerants in the liquid state. Gases are steam, evaporated refrigerants and the air-water vapor mixture found in the atmosphere. Some substances, including commonly used refrigerants, may exist in any of three states. A simple example is water, which may be solid (ice), liquid (water), or gas (steam or water vapor). STATIC HEAD - The pressure due to the weight of a fluid above the point of measurement. STATIC SUCTION HEAD - The positive vertical height in feet from the pump centerline to the top of the level of the liquid source.

STATIC SUCTION LIFT - The distance in feet between the pump centerline and the source of liquid below the pump centerline. STEAM - Water in vapor state. STEAM DRUM - A pressure chamber located at the upper extremity of a boiler circulatory system, in which the steam is generated in the boiler and separated from the water. STEAM JET REFRIGERATION - Refrigerating system which uses a steam venturi to create high vacuum (low pressure) on a water container causing water to evaporate at low temperature. STEAM PURITY - Refers to all matter but water in the steam. STEAM QUALITY - The percentage by weight of vapor in a steam and water mixture. STEAM-ABSORPTION CONDENSER - That part of a steam-absorption machine in which the water refrigerant is condensed by cooling-tower water and returned to the evaporator or chiller. STEAM-ABSORPTION MACHINE - A refrigeration or air-conditioning machine which uses, as a refrigerant, water evaporated by absorption in a brine regenerated by steam and condensed by cooling-tower water. STICTION (STATIC FRICTION) - Resistance of start of motion. STOICHIOMETRIC - The ratio of chemical substances reacting in the water that correspond to their combining weights in the theoretical chemical reaction. Stratified Air: Unmixed air in a duct that is in thermal layers that have temperature variations of more than five degrees. STRESS RAPTURE - A general type of damage referring to carbon steel tubing, when heated above 450°C. Material will plastically deform (creep) and then rapture. STUFFING BOX - That portion of the pump which houses the packing or mechanical seal, The stuffing box is usually referred to as the dry portion of the pump, and is located in back of the impeller and around the shaft.

SUBCOOLING - The difference between the temperature of a pure condensable fluid below saturation and the temperature at the liquid saturated state, at the same pressure. SUBCOOLING - The process of cooling a liquid to a temperature below its saturation temperature for any given saturation pressure. SUBLIMATION - A change of state directly from solid to gas without appearance of liquid. SUBLIMATION - Condition where a substance changes from a solid to a gas without becoming a liquid. SUCTION HEAD - The positive pressure on the pump inlet when the source of liquid supply is above the pump centerline. SUCTION LIFT - The combination of static suction lift and friction head in the suction piping when the source of liquid is below the pump centerline. SUCTION LINE - Tube or pipe used to carry refrigerant gas from evaporator to compressor. SUCTION PRESSURE - Pressure in low-pressure side of a refrigerating system. SUCTION PRESSURE CONTROL VALVE - Device located in the suction line which maintains constant pressure in evaporator during running portion of cycle. SUCTION PRESSURE CONTROL VALVE - Device located in the suction line which maintains constant pressure in evaporator during running portion of cycle. SUCTION SERVICE VALVE - Two-way manually operated valve located at the inlet to compressor. It controls suction gas flow and is used to service unit. SUCTION SIDE - Low-pressure side of the system extending from the refrigerant control through the evaporator to the inlet valve of the compressor. SULFATE - A compound, ion, or salt of sulfur and oxygen, such as sodium sulfate (Na2S04).

SULFITE DECOMPOSITION - Sodium sulfite, which is used as an oxygen scavenger, may decomposes with higher temperatures and concentration. The decomposition results in forming sulfur dioxide and thus leading to an acidic anhydride causing corrosion. SULFONIC - A specific acidic group (SO3H) on which depends the exchange activity of certain cation adsorbents. SULFUR DIOXIDE (SO2) - An old refrigerant. SUN EFFECT - Solar energy transmitted into space through windows and building materials. SUPERHEAT - The heat added to a fluid above its saturation point. SUPERHEATED STEAM - Steam heated above its saturation temperature. SUPERHEATED VAPOR - A vapor which is not about to condense. SUPERHEATER - Heat exchanger arranged to take heat from liquid going to evaporator and using it to superheat vapor leaving evaporator. SUPERHEATING - The process of adding heat to a vapor in order to raise its temperature above saturation temperature. It is impossible to superheat a saturated vapor as long as it is in contact with the liquid from which it is being generated; hence the vapor must be led away from the liquid before it can be superheated. SUPERSATURATED SOLUTION - A solution of a salt or mineral with a concentration beyond the normal saturation point. SURFACE BLOWDOWN - Removal of water, foam, etc. from the surface at the water level in a boiler. SURFACE HEATING - The exterior surface of a heating unit. Extended heating surface (or extended surface), consisting of fins, pins, or ribs which receive heat by conduction from the prime surface. Prime surface: heating surface having the heating medium on one side and air (or extended surface) on the other. SURFACE-SPRAY UNIT - A spray-coil unit.

SURFACTANT - A compound that affects interfacial tension between two liquids. It usually reduces surface tension. SURFACTANTS - A wetting agent used to prevent fouling, mainly in water cooling systems. SURGE - The sudden displacement or movement of water in a closed vessel or drum. SURGE SURPRESSOR - A device that reduces harmonic distortion in line voltage circuits by clipping off transient voltages which are fed through the power lines from operating equipment. SURGE TANK - Container connected to the low-pressure side of a refrigerating system which increases gas volume and reduces rate of pressure change. SUSPENDED SOLIDS - Un-dissolved solids in boiler water. SWAMP COOLER - Evaporative type cooler in which air is drawn through porous mats soaked with water. SWELLING - The expansion of an ion-exchange which occurs when the reactive groups on the resin are converted from one form to another. SYNERGISM - The combined action of several chemicals which produce an effect greater than the additive effects of each. SYSTEM - A series of ducts, conduits, elbows, branch piping, etc. designed to guide the flow of air, gas or vapor to and from one or more locations. A fan provides the necessary energy to overcome the resistance to flow of the system and causes air or gas flow through the system. Some components of a typical system are louvers, grilles, diffusers, filters, heating and cooling coils, air pollution control devices, burner assemblies, volume flow control dampers, mixing boxes, sound attenuators, the ductwork and related fittings. SYSTEM, CENTRAL FAN - A mechanical, indirect system of heating, ventilating, or air conditioning, in which the air is treated or handled by equipment located outside the rooms served, usually at a central location, and conveyed to and from the rooms by means of a fan and a system of distributing ducts.

SYSTEM, CLOSED - A heating or refrigerating piping system in which circulating water or brine is completely enclosed, under pressure above atmospheric, and shut off from the atmosphere except for an expansion tank. SYSTEM, DUCT - A series of ducts, conduits, elbows, branch piping, etc. designed to guide the flow of air, gas or vapor to and from one or more locations. A fan provides the necessary energy to overcome the resistance to flow of the system and causes air or gas to flow through the system. Some components of a typical system are louvers, grilles, diffusers, filters, heating and cooling coils energy recovery de vices, burner assemblies, volume dampers, mixing boxes, sound attenuators, the ductwork and related fittings. SYSTEM, FLOODED - A system in which only part of the refrigerant passing over the heat transfer surface is evaporated, and the portion not evaporated is separated from the vapor and recirculated. SYSTEM, UNITARY - A complete, factory-assembled and factory-tested refrigerating system comprising one or more assemblies which may be shipped as one unit or separately but which are designed to be used together. SYSTEMS CURVE - A graphic presentation of the pressure vs. volume flow rate characteristics of a particular system.

TAlL PIPE - Outlet pipe from the evaporator. TANDEM COMPOUND TURBINE - turbines are large turbines consisting of two or more turbines in series coupled together as one shaft and applied to one generator TANNINS - A chemical used as an inhibitor in relation with caustic embrittlement. TEMPERATURE - Degree of hotness or coldness as measured by a thermometer. TEMPERATURE CONTROL - Temperature-operated thermostatic device which automatically opens or closes a circuit. TEMPERATURE CRITICAL - The saturation temperature corresponding to the critical state of the substance at which the properties of the liquid and vapor are identical. Temperature, Absolute Zero: The zero point on the absolute temperature scale, 459.69 degrees below the zero of the Fahrenheit scale, 273.16 degrees be low the zero of the Celsius scale. TEMPERATURE, DEWPOINT - The temperature at which the condensation of water vapor in a space begins for a given state of humidity and pressure as the temperature of the vapor is reduced. The temperature corresponding to saturation (100 percent relative humidity) for a given absolute humidity at constant pressure. TEMPERATURE, DRYBULB - The temperature of a gas or mixture of gases indicated by an accurate thermometer after correction for radiation. TEMPERATURE, EFFECTIVE - An arbitrary index which combines into a single value the effect of temperature, humidity, and air movement on the sensation of warmth or cold felt by the human body. The numerical value is that of the temperature of still, saturated air which would induce an identical sensation. TEMPERATURE, SATURATION - The temperature at which no further moisture can be added to the air water vapor mixture. Equals dew point temperature.

TEMPERATURE, WET BULB - Thermodynamic wet bulb temperature is the temperature at which liquid or solid water, by evaporating into air, can bring the air to saturation adiabatically at the same temperature. Wet bulb temperature (without qualification) is the temperature indicated by a wet bulb psychrometer constructed and used according to specifications. TEMPERATURE-HUMIDITY INDEX - Actual temperature and humidity of air sample compared to air at standard conditions. TENSILE STRENGTH - In tensile testing, the ratio of maximum load to original cross-sectional area. Also called ultimate strength. TENSILE STRESS - A stress that causes two parts of an elastic body, on either side of a typical stress plane, to pull apart. TENSION - The force or load that produces elongation. TERMINAL VELOCITY - The maximum air stream velocity at the end of the throw. THE FIRST LAW - (1 ) When work is expanded in generating heat, the quantity of heat produced is proportional to the work expended; and, conversely, when heat is employed in the performance of work, the quantity of heat which disappears is proportional to the work done (Joule); (2) If a system is caused to change from an initial state to a final state by adiabatic means only, the work done is the same for all adiabatic paths connecting the two states (Zemansky); (3) In any power cycle or refrigeration cycle, the net heat absorbed by the working substance is exactly equal to the net work done. The Second Law: (1) It is impossible for a self acting machine, unaided by any external agency, to convey heat from a body of lower temperature to one of higher temperature (Clausius); (2) It is impossible to derive mechanical work from heat taken from a body unless there is available a body of lower temperature into which the residue not so Therm - Measurement used by gas utilities for billin3 purposes. 1 Therm = 100 cubic feet of gas = 100,000 Btu. THERM - Quantity of heat equal to 100000 Btu.

THERMAL CONDUCTIVITY - The rate at which heat is transferred through an object. THERMAL CONDUCTIVITY - The rate of heat flow, under steady conditions, through unit area, per unit temperature gradient in the direction perpendicular to the area. It is given in the SI nits s watts per meter Kelvin (W/m • K). THERMAL EFFICIENCY - Ratio of shaft work out of a system to the heat energy into the system. THERMAL EFFICIENCY OF A GAS TURBINE - Is the energy output of the gas turbine divided by the energy input of the gas turbine. THERMAL ELECTROMOTIVE FORCE - The electromotive force generated in a circuit containing two dissimilar metals when one junction is at temperature different from that of the other. (see also thermocouple). THERMAL EQUILIBRIUM - When two bodies originally at different temperatures, have attained the same temperature THERMAL EXPANSION - The change in length of a material with change in temperature. Thermal Expansion Valve: The metering device or flow control which regulates the amount of liquid refrigerant which is allowed to enter the evaporator. THERMAL SHOCK - The development of a steep temperature gradient and accompanying high stress within a material or structure. THERMAL TREATMENT - Refers to the treatment of water with heat to drive off the dissolved gases and soften certain minerals for easy removal. THERMISTOR - A two-terminal semiconductor device whose resistance is temperature sensitive. THERMOBANK - A bank for storing heat. THERMOCOUPLE - Device for measuring temperature utilizing the fact that an electromotive force is generated whenever two junctions of two dissimilar metals in an electric circuit are at different temperature levels.

THERMOCOUPLE - Device which generates electricity, using the principle that if two unlike metals are welded together and junction is heated, voltage will develop across the open ends. THERMOCOUPLE - Device which generates electricity, using the principle that if two unlike metals are welded together and junction is heated, voltage will develop across the open ends. THERMOCOUPLE THERMOMETER - Electrical instrument using thermocouple as source of electrical flow, connected to millimeter calibrated in temperature degrees. THERMODISK DEFROST CONTROL - Electrical switch with bimetal disk controlled by temperature changes. THERMODYNAMIC CYCLE THERMODYNAMIC PROPERTIES - Basic qualities used in defining the condition of a substance, such as temperature, pressure, volume, enthalpy, entropy. THERMODYNAMICS - Part of science which deals with the relationships between heat and mechanical action. THERMOELECTRIC REFRIGERATION - Where refrigeration is produced by the passage of electric current through two dissimilar materials. THERMOELECTRICITY - In physics, electricity generated by the application of heat to the junction of two dissimilar materials. If two wires of different materials are joined at their ends and one end is maintained at a higher temperature than the other, a voltage difference will arise, and an electric current will exist between the hot and the cold junctions. THERMOMETER - Device for measuring temperatures. THERMOMODULE - Number of thermocouples used in parallel to achieve low temperatures. THERMOPILE - Number of thermocouples used in series to create a higher voltage. THERMOSTAT - Device, which senses ambient temperature, conditions and, in turn, acts to control a circuit.

THERMOSTATIC CONTROL - Device which operates system or part of system based on temperature change. THERMOSTATIC VALVE - Valve controlled by temperature change response elements. THERMOSTATIC WATER VALVE - Valve used to control flow of water through system, actuated (made to work) by temperature difference. Used in units such as water-cooled compressor and/or condenser. THREE-WAY VALVE - Multi-orifice (opening) flow control valve with three fluid flow openings. THRESHOLD TREATMENT - Chemical treatment, used to prevent scale formation, which acts to hold hardness in solution at the threshold of precipitation. THROTTLE GOVERNING - With throttle governing a single large control valve controls the load from 0% to 100%When steam is throttled, the superheat increases and the turbine exhaust steam is drier, reducing the turbine blade erosion, but with the drier steam entering the condenser, the condenser losses increase. Throttling of steam through a valve is an isenthalpic ( constant enthalpy ) process and no heat is lost. The so-called throttling losses occur in the condenser. THROTTLING - An irreversible adiabatic steady flow process in which the fluid is caused to flow through an obstruction in a pipe with a resulting drop in pressure. THROTTLING RANGE - The amount of change in the variable being controlled to make the controlled device more through the full length of its stroke. THRUST COLLAR POSITION INDICATOR - The axial position of the rotor is very important and an axial position indicator is often applied to the thrust bearing. It may be a large dial micrometer with alarm setting for an axial movement of 0.4 millimeter and shutdown at 0.8 millimeter, or An oil pressure gauge connected to an oil leak-off device may also be used as an axial position indicator. The oil is supplied at say 500 kPa, flows through an orifice and leaks off through a nozzle. The pressure between the orifice and nozzle depends on the distance between the nozzle and shaft thrust collar; the larger the distance the lower the

pressure. The pressure gauge can be calibrated in millimeter clearance and may have alarm and shutdown settings TIMER-THERMOSTAT - Thermostat control which includes a clock mechanism. Unit automatically controls room temperature and changes temperature range depending on time of day. TIP SEALED BLADES TITRATION - A chemical process used in analyzing feed water. TON REFRIGERATION UNIT - Unit which removes same amount of heat in 24 hours as melting of 1 ton of ice. TON'S OF REFRIGERATION - The capacity of a refrigeration system that can freeze 1 ton (1000 kg) of liquid water at 0°C into ice at 0°C in 24 hour is said to be 1 tone. TOOL STEEL - Any steel used o make tools for cutting, forming, or otherwise shaping a material into a final part. TOPPING TURBINE - Have been used when old boilers are replaced with new high pressure boilers. The turbine is a backpressure turbine exhausting to the old boiler header still supplying steam to the old lower pressure turbines. TOTAL DYNAMIC HEAD - Dynamic discharge head (static discharge head, plus friction head, plus velocity head) plus dynamic suction lift, or dynamic discharge head minus dynamic suction head. TOTAL HARDNESS - See Hardness. TOTAL HEAT - Sum of both the sensible and latent heat. TOTAL HEAT (ENTHALPY) - Total heat is the sum of the sensible heat and latent heat in an exchange process. In many cases, the addition or subtraction of latent and sensible heat at terminal coils appears simultaneously. Total heat also is called enthalpy, both of which can be defined as the quantity of heat energy contained in that substance. TOTAL SOLIDS - Are the sum of the dissolved and suspended solids. TOWER FILL - The interior structure of a cooling tower over which the water flows.

TRACE CONSTITUENTS - Materials present at a concentration less than 0.01 mg/L. TRANSMITTANCE, THERMAL (U FACTOR) - The time rate of heat flow per unit area under steady conditions from the fluid on the warm side of a barrier to the fluid on the cold side, per unit temperature difference between the two fluids. TRANSDUCER - The means by which the controller converts the signal from the sensing device into the means necessary to have the appropriate effect on the controlled device. For example, a change in air pressure in the pneumatic transmission piping. TRANSFORMER - The system power supplying transformer is an inductive stationary device which transfers electrical energy from one circuit to another. The transformer has two windings, primary and secondary. A changing voltage applied to one of these, usually the primary, induces a current to flow in the other winding. A coupling transformer transfers energy at the same voltage; a step-down transformer transfers energy at a lower voltage, and a step-up transformer transfers energy at a higher voltage. TRANSIENT CONSTITUENTS - Are those constituents which change in concentration or activity by changes in the aquatic environment. The change my be due to oxidation potentials, biological activities, etc.. TRANSISTOR - An active semiconductor device capable of providing power amplification and having three or more terminals. TREATMENT - A process whereby impurities are removed from water; also a substance added to water to improve its physical or chemical properties. TRIBOLOGY - The science concerned with the design, friction, lubrication and wear of contacting surfaces that move relative to each other (as in bearings, cams, or gears). TUBE SHEET - The portion of a heat exchanger or boiler in to which the tubes are rolled or secured. TUBERCLE - A protective crust of corrosion products (rust) which builds up over a pit caused by the loss of metal due to corrosion.

TUBERCULATION - A corrosion process that produces hard knob-like mounds of corrosive products on metal surfaces, increasing friction and reducing flow in a water distribution system. TUBE-WITHIN-A-TUBE - Water-cooled condensing unit in which a small tube is placed inside large unit. Refrigerant passes through outer tube, water through the inner tube. TURBIDITY - The measure of suspended matter in, a water sample which contributes to the reflection of light or cloudiness. TURBIDITY UNIT - The unit of measure of suspended matter in water. It is the measure of light compared against light reflected by a reference standard as defined by the standard methods of water analysis in, APHA. TURBINE METER - A device used to measure water consumption in industrial plants. TURBINE ROTOR - The rotating assembly enclosed within the turbine casing TURNER GAUGE - A device used to measure the actual scale-thickness in boiler tubes. TWO-TEMPERATURE VALVE - Pressure-opened valve used in suction line on multiple refrigerator installations, which maintains evaporators in a system at different temperatures. TWO-WAY VALVE - Valve with one inlet port and one outlet port.

ULTIMATE STRENGTH - The maximum stress (tensile, compressive or shear) a material can sustain without fracture. It is determined by dividing maximum load by the original cross-sectional area of the specimen. ULTRA FILTRATION - A process that forces water through a filtering membrane by means of pressure gradients in order to obtain ultra pure water. UNDER DEPOSIT ATTACK - Corrosion under or around a localized deposit on a metal surface (a form of crevice corrosion). UNITARY SYSTEM - A room unit which performs part or all of the air conditioning functions. It may or may not be used with a central fan system. UNLOADER - A device in or on the compressor for equalizing high-side and low-side pressures for a brief time during starting and for controlling compressor capacity by rendering one or more cylinders ineffective. UP FLOW - The operation of an ion-exchange unit in which solutions are passed in at the bottom and out at the top of the container. UP FLOW FILTER - A unit containing a single filter medium, usually with graded sand. UP FLOW FURNACE - A furnace in which the heated air flows upward as it leaves the furnace. UPSTREAM - The inlet side of an instrument, a pump, valve, etc.. UTILITY TRANSFORMER - Primary and secondary coils of wire which reduce (step down) the utility supply volt age for use within a facility. U-TUBE MANOMETER - A U-shaped section of plastic or glass tubing that is partially filled with water or mercury. They are used to measure the lower pressure ranges of gases.

VACUUM - Pressure lower than atmospheric pressure. VACUUM BREAKER - A device to prevent a suction in a water pipe. VACUUM PUMP - Special high efficiency device used for creating high vacuums for testing or drying purposes. VALVE, MODULATING - A valve which can be positioned anywhere between fully on and fully off to proportion the rate of flow in response to a modulating controller (see modulating control). VALVE, NEEDLE - A form of globe valve that contains a sharp pointed, needle like plug that is driven into the and out of a cone shaped seat to accurately control a relatively small rate of flow of a fluid. VALVE, POP - A spring loaded safety valve that opens automatically when pressure exceeds the limits for which the valve is set. It is used a safety device on pressurized vessels and other equipment to prevent damage from excessive pressure, also called relief valve or a safety valve. VALVE, POPPET - A device that controls the rate of flow of fluid in a line or opens or shuts of the flow of fluid completely. When open, the sealing surface of the valve is moved away from a seat. When closed, the sealing surface contacts the seat to shut of the flow. Poppet valves are used extensively as pneumatic controls and as intake and exhaust valves in most internal combustion engines. VALVE, PRESSURE RELIEF - A valve designed to minimize the possibility of explosion when air temperature surrounding a refrigeration system may rise to a point where the pressure of the refrigerant gas to increase to a danger point. VALVE, RELIEF - Also called pressure relief valve. VALVE, TWO-POSITION - A valve which is either fully on or fully off with no positions between. Also called an "on-off valve". VANE - That portion of an impeller which throws the water toward the volute case. VAPOR - A gas, particularly one near to equilibrium with the liquid phase of the substance and which does not follow the gas laws.

Usually used instead of gas for a refrigerant, and, in general, for any gas below the critical temperature. VAPOR BARRIER - A moisture-impervious layer applied to the surfaces enclosing a humid space to prevent moisture travel to a point where it may condense due to lower temperature. VAPOR LOCK - A condition where liquid flow is impeded by vapor trapped in a liquid line. VAPOR PHASE VAPOR PHASE INHIBITORS - A system using an organic nitrite compound, a powder which vaporizes slowly to protect ferrous metal from contact with oxygen. VAPOR PRESSURE - Vapor pressure denotes the lowest absolute pressure that a given liquid at a given temperature will remain liquid before evaporating into its gaseous form or state. VAPOR, SATURATED - Vapor in equilibrium with its liquid; i.e., when the numbers per unit time of molecules passing in two directions through the surface dividing the two phases are equal. VAPOR, SUPERHEATED - Vapor at a temperature which is higher than the saturation temperature (i.e., boiling point) at the existing pressure. VAPOR, WATER - Water used commonly in air conditioning parlance to refer to steam in the atmosphere. VAPOROUS CARRYOVER - Referring to impurities carried over with the steam and then forming a deposit on turbine bladings. This type of carryover is difficult to prevent. VELOCITY - A vector quantity which denotes, at once, the time rate and the direction of a linear motion. VELOCITY COMPOUNDING VELOCITY HEAD - The vertical distance a liquid must fall to acquire the velocity with which it flows through the piping system. For a given quantity of flow, the velocity head will vary indirectly as the pipe diameter varies.

VELOCITY, TERMINAL - The highest sustained air stream velocity existing in the mixed air path at the end of the throw. VENT - An opening in a vessel or other enclosed space for the removal of gas or vapor. VENTILATION - The process of supplying or removing air by natural or mechanical means, to or from a space; such air may or may not have been conditioned. VENTURI TUBE METER - A flow meter used to determine the rate of flow and employing a venturi tube as the primary element for creating differential pressure in flowing gases or liquids. VISCOSITY - That property of semi-fluids, fluids, and gases by virtue of which they resist an instantaneous change of shape or arrangement of parts. It is the cause of fluid friction whenever adjacent layers of fluid move with relation to each other. VISCOSITY INDEX - A commonly used measure of the change in viscosity of a fluid with temperature. The higher the viscosity index, the smaller the relative change in viscosity with temperature. VITAL HEAT - The heat generated by fruits and vegetables in storage; caused by ripening. VOLATILE SOLIDS - Those solids in water or other liquids that are lost on ignition of dry solids at 550°F. VOLATILE TREATMENT - Based on the use of hydrazine and neutralizing amines or ammonia. Leaves no solids in the boiler. VOLATILITY - Volatility, surface tension and capillary action of a fluid are incidental to environmental systems. Volatility is the rapidity with which liquids evaporates extremely rapidly and therefore is highly volatile. VOLT - The unit of potential difference or electromotive force in the meter-kilogram-second system, equal to the potential difference between two points for which 1 coulomb of electricity will do 1 joule of work in going from one point to another.

VOLTAGE (E) - The electromotive force in an electrical circuit. The difference in potential between two unlike charges in an electrical circuit is its voltage measured in "volts" (V). VOLTAGE DROP - The voltage drop around a circuit including wiring and loads must equal the supply volt age. VOLTAIC CELL - A storage device that converts chemical to electrical energy. VOLUME, SPECIFIC - The volume of a substance per unit mass; the reciprocal of density. VOLUTE - The spiral-shaped casing surrounding a pump impeller that collects the liquid discharged by the impeller.

WALK-IN-COOLER - A large commercial refrigerated space often found in supermarkets or places for whole sale distribution. WASTE WATER - The used water and solids from industrial processes that flow to a treatment plant. WATER - A tasteless, odorless, colorless liquid in its pure state. WATER ABSORPTION - The amount of weight gain (%) experienced in a polymer after immersion in water for a specific length of time under controlled environment. WATER HAMMER - Banging of pipes caused by the shock of closing valves (faucets). WATER LUBRICANT - Water used as a lubricant; for example, in a mechanical seal on a centrifugal water pump. WATER SEALED GLAND WATER SOFTENER - A device or system used to remove calcium and magnesium hardness minerals from a water supply. WATER TUBE - A boiler tube through which the fluid under pressure flows. The products of combustion surround the tube. WATER VAPOR - In air conditioning, the water in the atmosphere. WATER, BRAKISH - (1) Water having less salt than sea water, but undrinkable. (2) Water having salinity values ranging from about 0.5 to 17 parts per thousand. WATER, POTABLE - Water that is safe to drink. WATER, SOUR - Waste waters containing fetid materials, usually sulfur compounds. WATER-ICE REFRIGERATION SYSTEM - Heat is absorbed as ice melts and thus producing a cooling effect. WATER LEG - That space that is full of boiler water between two parallel plates. It usually forms one or more sides of internally fired boilers.

WATER WALL - A row of water tubes lining a furnace or combustion chamber, exposed to the radiant heat of the fire. WATT (W) - A measure of electric power equal to a current flow of one ampere under one volt of pressure; or one joule per second in SI units. WEIGHT TO POWER RATIO - It is the weight of the machine producing work. For example - the gas turbine is capable of producing more horse power per given mass of its machinery, then the same amount of horse power produced by a machine having many times that mass. WET BULB - Device used in measurement of relative humidity. Evaporation of moisture lowers temperature of wet bulb compared to dry bulb temperature in same area. WET BULB TEMPERATURE (WB) - The temperature registered by a thermometer whose bulb is covered by a saturated wick and exposed to a current of rapidly moving air. The wet bulb temperature also represents the dew point temperature of the air, where the moisture of the air condenses on a cold surface. WET STANDBY - Boiler is filled completely with water or maintained at normal operating level with a positive nitrogen pressure of 35 to 70 kPa. WET-BULB DEPRESSION - The difference between the dry-bulb temperature and the wet bulb temperature. Willans Line - The Willians line is used to show steam rates at different loads on the turbine. Often, a willans line for a specific turbine is not available, and one only has has incomplete information about an installed steam turbine; namely the rated power and (perhaps a guesstimate) the isentropic efficiency or specific steam consumption at full load. But what you need and don't have is the steam consumption at the turbine operating load. WIND AGE DRIFT - That water lost from an open re-circulating-water system by means of wind blown through the spray area that carries water out of the system. This is not the same as loss by evaporation, since such a loss can occur even without evaporation. WOBBLE PLATE-SWASH PLATE - Type of compressor designed to compress gas, with piston motion parallel to crankshaft.

WORKING FLUID - is the substance which does the work in a heat engine. The air is one of the working fluids used with gas turbines. Freon's are the working fluids used with some refrigeration systems. Water is the working fluid used with steam boilers.

ZEOLITE - A natural mineral (hydrous silicates) that has the capacity to absorb hardness, calcium, and magnesium ions from water. ZEOLITE SOFTENING - Refers to the process, where zeolite chemicals are capable to exchange ions with the hardness causing impurities of the water. ZETA POTENTIAL - The difference in voltage between the surface of the diffuse layer surrounding a colloidal particle and the bulk liquid beyond. ZONING - The practice of dividing a building into small sections for heating and cooling control. Each section is selected so that one thermostat can be used to determine its requirements.

A ablation (glacial) All processes, which include melting, evaporation (sublimation), wind erosion, and calving (breaking off of ice masses), that remove snow or ice from a glacier or snowfield. The term also refers to the amount of snow or ice removed by these processes. abscission Shedding by a plant of its parts, such as leaves, flowers, fruits, or seeds. The process is regulated by the plant hormone abscisic acid. absorption coefficient A measure of the amount of radiant energy, incident normal to a planar surface, that is absorbed per unit distance or unit mass of a substance. acclimation (acclimatization) Change that occurs in an organism to allow it to tolerate a new environment. accumulation (glacial) All processes, which include snowfall, condensation, avalanching, snow transport by wind, and freezing of liquid water, that add snow or ice to a glacier, floating ice, or snow cover. The term also includes the amount of snow or other solid precipitation added to a glacier or snowfield by these processes. acidity profile The acid concentration in ice core layers as a function of depth as determined from electrical measurements. The magnitudes of some volcanic eruptions in the Northern Hemisphere have been estimated from the acidity of annual layers in ice cores taken in Greenland. This methodology is sometimes referred to as acidity signal or acidity record.

adaptation The adjustment of an organism or population to a new or altered environment through genetic changes brought about by natural selection. adiabatic process A thermodynamic change of state of a system such that no heat or mass is transferred across the boundaries of the system. In an adiabatic process, expansion always results in cooling, and compression in warming. adiabatic warming See adiabatic process. advection The predominately horizontal large-scale movement of air that causes changes in temperature or other physical properties. In oceanography, advection is the horizontal or vertical flow of sea water as a current. aerosol Particulate material, other than water or ice, in the atmosphere ranging in size from approximately 10x-3 to larger than 10x2 ?m in radius. Aerosols are important in the atmosphere as nuclei for the condensation of water droplets and ice crystals, as participants in various chemical cycles, and as absorbers and scatterers of solar radiation, thereby influencing the radiation budget of the earth-atmosphere system, which in turn influences the climate on the surface of the Earth. agglomeration In meteorology, the process by which precipitation particles grow larger by collision or contact with cloud particles or other precipitation particles. Agung Active volcano 10,380 ft (3,141 m) high in Bali, Indonesia. Last eruption was in 1964. airborne fraction

The portion of CO2 released from all energy consumption and land use activities that remains in the atmosphere as opposed to the amounts absorbed by plants and oceans. How the world's total carbon is partitioned among the oceanic, terrestrial, and atmospheric pools is determined by complex biogeochemical and climatological interactions. airborne particulates Total suspended matter found in the atmosphere as solid pieces or liquid droplets. Airborne particulates include windblown dust, emissions from industrial processes, smoke from the burning of wood and coal, and the exhaust of motor vehicles. airmass A widespread body of in the atmosphere that gains certain meteorological or polluted characteristics while set in one location. The characteristics can change as it moves away. albedo The fraction of the total solar radiation incident on a body that is reflected by it. Alfisols An order of soils with a medium-to-high base supply, horizons of clay accumulation, and gray-brown surface horizons. algae Simple rootless plants that grow in sunlit waters in relative proportion to the amounts of nutrients available. They are food for fish and small aquatic animals. algal blooms Sudden spurts of algal growth that can indicate potentially hazardous changes in local water chemistry. alkalinity A pressure- and temperature-independent property of seawater that determines in part the carbon content of seawater. Carbonate alkalinity is the sum of the concentration of bicarbonate plus two times the concentration of the

carbonate ions. Total alkalinity is the amount of acid required to bring seawater to a pH at which all dis- solved inorganic carbon becomes freely exchangeable. The alkalinity of the oceans is determined with potentiometric or normal titration techniques that detect and measure the presence of bicarbonate, carbonate, and borate ions. altithermal period A period of high temperature, particularly the one from 8000 to 4000 B.P. (before the present era), which was apparently warmer in summers, as compared with the present, and with the precipitation zones shifted poleward. Also called the hypsithermal period. anadromous Fish that spend their adult lives in the sea but swim upriver to freshwater spawning grounds to reproduce. analog (climate) A large-scale weather pattern of the past that is similar to a current situation in its essential characteristics. Antarctic Ice Sheet See ice sheet. anthropogenic Man made. Usually used in the context of emissions that are produced as the result of human activities. anticyclone (high-pressure area) An atmospheric high-pressure closed circulation with clockwise rotation in the Northern Hemisphere, counterclockwise in the Southern Hemisphere, and undefined at the Equator. aragonite A mineral species of calcium carbonate (CaCO3) with a crystal structure different from that of vaterite and calcite, which are the other two forms of CaCO3. It is precipitated from ocean surface waters mainly by organisms (e.g., coral) that use it to make their shells and skeletons. Arctic haze

A persistent winter diffuse layer in the Arctic atmosphere whose origin may be related to long-range transport of midlatitude continental man-made pollutants. atmosphere (An) A standard unit of pressure representing the pressure exerted by a 29.92-in. column of mercury at sea level at 45 degrees latitude and equal to 1000 g/cm2. atmosphere (The) The envelope of air surrounding the Earth and bound to it by the Earth's gravitational attraction. Studies of the chemical properties, dynamic motions, and physical processes of this system constitute the field of meteorology. atmospheric turbulence A state of the flow of air in which apparently random irregularities occur in the air's instantaneous velocities, often producing major deformations of the flow. atmospheric window The spectral region between 8.5 and 11.0 microns where the atmosphere is essentially transparent to longwave radiation. autotrophic An organism that produces food from inorganic substances.

B baroclinic model A model of atmospheric circulation that, in contrast with barotropic models, does not constrain constant-pressure surfaces to coincide with constant-density surfaces. basal sliding (basal slip) The movement or speed of movement of a glacier on its bed. bathymetry The science of measuring ocean depths to determine the topography of the sea floor. benthic organism (benthos) A form of aquatic plant or animal life that is found on or near the bottom of a stream, lake, or ocean. benthic region The bottom layer of a body of water. biogeochemical cycle The chemical interactions among the atmosphere, biosphere, hydrosphere, and lithosphere. biological productivity The amount of organic matter, carbon, or energy content that is accumulated during a given time period. biomass The total dry organic matter or stored energy content of living organisms that is present at a specific time in a defined unit (community, ecosystem, crop, etc.) of the Earth's surface. biosphere The portion of Earth and its atmosphere that can support life. The part (reservoir) of the global carbon cycle that includes living organisms (plants and animals) and lifederived organic matter (litter, detritus). The terrestrial biosphere includes the living biota (plants and animals) and the litter and soil organic matter on land, and the marine biosphere includes the biota and detritus in the oceans.

biota The animal and plant (fauna and flora) life of a given area. bitumen Dark, naturally occurring solid or semisolid substances composed mainly of a mixture of hydrocarbons with little oxygen, nitrogen, or sulfur. buffer factor (Revelle factor) The ratio of the instantaneous fractional change in the partial pressure of CO2 (pCO2) exerted by seawater to the fractional change in total CO2 dissolved in the ocean waters. The buffer factor relates the partial pressure of CO2 in the ocean to the total ocean CO2 concentration at constant temperature, alkalinity and salinity. The Revelle factor is a useful parameter for examining the distribution of CO2 between the atmosphere and the ocean, and measures in part the amount of CO2 that can be dissolved in the mixed surface layer.

C C3 plants Plants (e.g., soybean, wheat, and cotton) whose carbonfixation products have three carbon atoms per molecule. Compared with C4 plants, C3 plants show a greater increase in photosynthesis with a doubling of CO2 concentration and less decrease in stomatal conductance, which results in an increase in leaf-level water-use efficiency. C4 plants Plants (e.g., maize and sorghum) whose carbon fixation products have four carbon atoms per molecule. Compared with C3 plants, C4 plants show little photosynthetic response to increased CO2 concentrations above 340 ppm but show a decrease in stomatal conductance, which results in an increase in photosynthetic water-use efficiency. calcrete A surficial gravel and sand conglomerate cemented by calcium carbonate. caliche Also called hardpan; an opaque, reddish-brown-to-white calcareous material, which occurs in layers near the surface of stony soils in arid and semiarid areas. Calvin cycle The incorporation of CO2 into glucose by enzymatic reactions. CAM plants (crassulacean acid metabolism) Plants (e.g, cactus and other succulents) that, unlike the C3 and C4 plants, temporarily separate the processes of carbon dioxide uptake and fixation when grown under arid conditions. They take up gaseous carbon dioxide at night when the stomata are open and water loss is minimal. During the day when the stomata are closed, the stored CO2 is released and chemically processed. When CAM plants are not under water stress, they then follow C3 photosynthesis.

canopy The branches and leaves of woody plants that are formed some distance above the ground. carbon-based resources The recoverable fossil fuel (coal, gas, crude oils, oil shale, and tar sands) and biomass that can be used in fuel production and consumption. carbon budget The balance of the exchanges (incomes and losses) of carbon between the carbon reservoirs or between one specific loop (e.g., atmosphere - biosphere) of the carbon cycle. An examination of the carbon budget of a pool or reservoir can provide information about whether the pool or reservoir is functioning as a source or sink for CO2. carbon cycle All parts (reservoirs) and fluxes of carbon; usually thought of as a series of the four main reservoirs of carbon interconnected by pathways of exchange. The four reservoirs, regions of the Earth in which carbon behaves in a systematic manner, are the atmosphere, terrestrial biosphere (usually includes fresh water systems), oceans, and sediments (includes fossil fuels). Each of these global reservoirs may be subdivided into smaller pools ranging in size from individual communities or ecosystems to the total of all living organisms (biota). Carbon exchanges from reservoir to reservoir by various chemical, physical, geological, and biological processes. carbon density The amount of carbon per unit area for a given ecosystem or vegetation type, based on climatic conditions, topography, vegetative-cover type and amount, soils, and maturity of the vegetative stands. carbon dioxide fertilization Enhancement of plant growth or of the net primary production by CO2 enrichment that could occur in natural or

agricultural systems as a result of an increase in the atmospheric concentration of CO2. carbon dioxide reference gas A mixture of a known quantity of CO2-in air or CO2-in-N2 used to calibrate carbon dioxide analyzers. carbon flux The rate of exchange of carbon between pools (reservoirs). carbon isotope ratio Ratio of carbon-12 to either of the other, less common, carbon isotopes, carbon- 13 or carbon-14. carbon pool The reservoir containing carbon as a principal element in the geochemical cycle. carbon sink A pool (reservoir) that absorbs or takes up released carbon from another part of the carbon cycle. For example, if the net exchange between the biosphere and the atmosphere is toward the atmosphere, the biosphere is the source, and the atmosphere is the sink. carbon source A pool (reservoir) that releases carbon to another part of the carbon cycle. catanadromous Fish that swim downstream to spawn. Chernozem (Tchernozem) A major group of dark-colored zonal soils with a rich and deep humus horizon occurring in temperate-to-cool, subhumid climates. chlorofluorocarbons A family of inert nontoxic and easily liquified chemicals used in refrigeration, air conditioning, packaging, and insulation or as solvents or aerosol propellants. Because they are not destroyed in the lower atmosphere, they drift into the upper atmosphere where their chlorine components destroy ozone. chloroplast

An organelle in the cells of green plants. It contains chlorophyll and functions in photosynthesis and protein synthesis. clear cutting A forest-management technique that involves harvesting all the trees in one area at one time. climate The statistical collection and representation of the weather conditions for a specified area during a specified time interval, usually decades, together with a description of the state of the external system or boundary conditions. The properties that characterize the climate are thermal (temperatures of the surface air, water, land, and ice), kinetic (wind and ocean currents, together with associated vertical motions and the motions of air masses, aqueous humidity, cloudiness and cloud water content, groundwater, lake lands, and water content of snow on land and sea ice), nd static (pressure and density of the atmosphere and ocean, composition of the dry ir, salinity of the oceans, and the geometric boundaries and physical constants of the system). These properties are interconnected by the various physical processes such as precipitation, evaporation, infrared radiation, convection, advection, and turbulence. climate change The long-term fluctuations in temperature, precipitation, wind, and all other aspects of the Earth's climate. External processes, such as solar-irradiance variations, variations of the Earth's orbital parameters (eccentricity, precession, and inclination), lithosphere motions, and volcanic activity, are factors in climatic variation. Internal variations of the climate system also produce fluctuations of sufficient magnitude and variability to explain observed climate change through the feedback processes interrelating the components of the climate system. climate sensitivity

The magnitude of a climatic response to a perturbing influence. In mathematical modeling of the climate, the difference between simulations as a function of change in a given parameter. climate signal A statistically significant difference between the control and disturbed (see climate sensitivity) simulations of a climate model. climate system The five physical components (atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere) that are responsible for the climate and its variations. climate variation The change in one or more climatic variables over a specified time. climatic analog A past climate situation in which changes similar to the present occurred. Used in making climatic projections. climatic anomaly The deviation of a particular climatic variable from the mean or normal over a specified time. climatic optimum The period in history from about 5000 to about 2500 B.C. during which surface air temperatures were warmer than at present in nearly all regions of the world. In the Arctic region, the temperature rose many degrees, and in temperate regions, the increase was 1.0 degrees - 1.7 degrees C. In this period, glaciers and ice sheets receded greatly, and the meltwater raised sea level by about 3 meters. cloud A visible mass of condensed water vapor particles or ice suspended above the Earth's surface. Clouds may be classified on their visible appearance, height, or form. cloud albedo

Reflectivity that varies from less than 10 to more than 90% of the insolation and depends on drop sizes, liquid water content, water vapor content, thickness of the cloud, and the sun's zenith angle. The smaller the drops and the greater the liquid water content, the greater the cloud albedo, if all other factors are the same. cloud feedback The coupling between cloudiness and surface air temperature in which a change in surface temperature could lead to a change in clouds, which could then amplify or diminish the initial temperature perturbation. For example, an increase in surface air temperature could increase the evaporation; this in turn might increase the extent of cloud cover. Increased cloud cover would reduce the solar radiation reaching the Earth's surface, thereby lowering the surface temperature. This is an example of negative feedback and does not include the effects of longwave radiation or the advection in the oceans and the atmosphere, which must also be considered in the overall relationship of the climate system. coastal zone Lands and waters adjacent to the coast that exert an influence on the uses of the sea and its ecology or whose uses and ecology are affected by the sea. composting The natural biological decomposition of organic material in the presence of air to form a humus-like material. continental crust The layer of the Earth that lies under continents and the continental shelves. It ranges in thickness from 35 to 60 km. Its upper layer has a density of 2.7 g/cm3 and is composed of rocks that are rich in silica and alumina. continental plate A thick continental crust. continental shelves

Those parts of the continent that are covered by water. They are several to more than 322 km wide and about 122 m deep. At the edges of the shelves, the continental slopes drop rapidly from 100 to 200 m to 3000 to 3700 m. continental slopes See continental shelves. convection Atmospheric or oceanic motions that are predominately vertical and that result in vertical transport and mixing of atmospheric or oceanic properties. Because the most striking meteorological features result if atmospheric convective motion occurs in conjunction with the rising current of air (i.e., updrafts), convection is sometimes used to imply only upward vertical motion. convective adjustment A numerical procedure applied in many atmospheric models to approximate the vertical nonradiative heat transport. This procedure adjusts the lapse rate whenever necessary so that some prescribed critical lapse rate is never exceeded. convergence The quasi-horizontal flow of a fluid toward a common destination from different directions. When waters of different origins come together at a point or along a line (convergence line), the denser water from one side sinks under the lighter water from other side. The ocean convergence lines are the polar, subtropical, tropical, and equatorial. Also see divergence. Coriolis effect The tendency for an object moving above the Earth to turn to the right in the Northern Hemisphere and to the left in the Southern Hemisphere relative to the Earth's surface. The effect arises because the Earth rotates and is not, therefore, an inertial reference frame. cotyledon

A leaf or leaves of the embryos of seed plants. They can function in food storage and can become photosynthetic when the seed germinates. crop water-use efficiency A measure at the ecosystem level of how well plants use available water in growth. The grams of dry weight gained by plants during the growing season per unit land area are divided by the millimeters of water lost (including evaporation directly from the soil). cryosphere The portion of the climate system consisting of the world's ice masses and snow deposits, which includes the continental ice sheets, mountain glaciers, sea ice, surface snow cover, and lake and river ice. Changes in snow cover on the land surfaces are by and large seasonal and closely tied to the mechanics of atmospheric circulation. The glaciers and ice sheets are closely related to the global hydrologic cycle and to variations of sea level and change in volume and extent over periods ranging from hundreds to millions of years.

D decomposers Heterotrophic organisms that break down dead protoplasm and use some of the products and release others for use by consumer organisms. decomposition The breakdown of matter by bacteria and fungi. It changes the chemical makeup and physical appearance of materials. deep water That part of the ocean below the main thermocline. deforestation The removal of forest stands by cutting and burning to provide land for agricultural purposes, residential or industrial building sites, roads, etc. or by harvesting the trees for building materials or fuel. Oxidation of organic matter releases CO2 to the atmosphere, and regional and global impacts may result. dendrochronology The dating of past events and variations in the environment and the climate by studying the annual growth rings of trees. The approximate age of a temperate forest tree can be determined by counting the annual growth rings in the lower part of the trunk. The width of these annual rings is indicative of the climatic conditions during the period of growth; wide annual rings signify favorable growing conditions, absence of diseases and pests, and favorable climatic conditions, while narrow rings indicate unfavorable growing conditions or climate. dendroclimatology The use of tree growth rings as proxy climate indicators. Tree rings record responses to a wider range of climatic variables over a larger part of the Earth than any other type of annually dated proxy record. desertification

The progressive destruction or degradation of vegetative cover especially in arid or semiarid regions bordering existing deserts. Overgrazing of rangelands, large-scale cutting of forests and woodlands, drought, and burning of extensive areas all serve to destroy or degrade the land cover. The climatic impacts of this destruction include increased albedo leading to decreased precipitation, which in turn leads to less vegetative cover; increased atmospheric dust loading could lead to decreased monsoon rainfall and greater wind erosion and/or atmospheric pollution. differentiation The process by which single cells grow into particular forms of specialized tissue (e.g., root, stem, or leaf). divergence A horizontal flow of water, in different directions, from a common center or zone; it is often associated with upwelling. Also see convergence. downwelling The process of accumulation and sinking of warm surface waters along a coastline. A change of air flow of the atmosphere can result in the sinking or downwelling of warm surface water. The resulting reduced nutrient supply near the surface affects the ocean productivity and meteorological conditions of the coastal regions in the downwelling area. dust veil index A quantitative method developed by H. H. Lamb for comparing the magnitude of volcanic eruptions. The formulae use observations either of the depletion of the solar beam, temperature lowering in middle latitudes, or the quantity of solid matter dispersed as dust. The reference dust veil index is 1000, assigned to the Krakatoa 1883 eruption, and the index is calculated using all three methods, where the information is available, for statistical comparison purposes. Abbreviated D.V.I.

E ecosystem The interacting system of a biological community and its nonliving environmental surroundings. eddy A circular movement of water or air that is formed where currents pass obstructions or between two adjacent currents that are flowing counter to each other. El Chicon Active volcano 7300 ft (2225 m) high in Mexico. The last eruption was in 1983. El Nino An irregular variation of ocean current that from January to March flows off the west coast of South America, carrying warm, low-salinity, nutrient-poor water to the south. It does not usually extend farther than a few degrees south of the equator, but occasionally it does penetrate beyond 12 degrees S, displacing the relatively cold Peru Current. The effects of this phenomenon are generally short-lived, and fishing is only slightly disrupted. Occasionally (in 1891, 1925, 1941, 1957 - 58, 1965, 1972 - 73, 1976, and 1982 - 83), the effects are major and prolonged. Under these conditions, sea surface temperatures rise along the coast of Peru and in the equatorial eastern Pacific Ocean and may remain high for more than a year, having disastrous effects on marine life and fishing. Excessive rainfall and flooding occur in the normally dry coastal area of western tropical South America during these events. Some oceanographers and meteorologists consider only the major, prolonged events as El Nino phenomena rather than the annually occurring weaker and short-lived ones. The name was originally applied to the latter events because of their occurrence at Christmas time. emissions

Materials (gases, particles, vapors, chemical compounds, etc.) that come out of smokestacks, chimneys, and tailpipes. emissivity The ratio of the radiation emitted by a surface to that emitted by a black body at the same temperature. energy balance models An analytical technique to study the solar radiation incident on the Earth in which explicit calculations of atmospheric motions are omitted. In the zero- dimensional models, only the incoming and outgoing radiation is considered. The outgoing infrared radiation is a linear function of global mean surface air temperature, and the reflected solar radiation is dependent on the surface albedo. The albedo is a step function of the global meansurface air temperatures, and equilibrium temperatures are computed for a range of values of the solar constant. The one-dimensional models have surface air temperature as a function of latitude. At each latitude, a balance between incoming and outgoing radiation and horizontal transport of heat is computed. (Abbreviated as EBM.) environment The sum of all external conditions affecting the life, development, and survival of an organism. epidemiology The study of diseases as they affect populations, including the distribution of disease or other health-related states and events in human populations, the factors (e.g., age, sex, occupation, and economic status) that influence this distribution, and the application of this study to control health problems. equilibrium line The level on a glacier where accumulation equals ablation and the net balance equals zero. estuary

Regions of interaction between rivers and near-shore ocean waters, where tidal action and river flow create a mixing of fresh and salt water. euphotic zone The layer of a body of water that receives sufficient sunlight for photosynthesis. The depth of this layer, which is about 80 m, is determined by the water's extinction coefficient, the cloudiness, and the sunlight's angle of incidence. evapotranspiration Discharge of water from the Earth's surface to the atmosphere by evaporation from bodies of water, or other surfaces, and by transpiration from plants.

F feedback mechanisms A sequence of interactions in which the final interaction influences the original one. Also see positive feedback and negative feedback. fen A type of wetland that accumulates peat deposits; they are less acidic than bogs, deriving most of their water from groundwater rich in calcium and magnesium. firn Material that is transitional between snow and glacier ice. It is formed from snow after passing through one summer melt season and becomes glacier ice after its permeability to liquid water falls to zero. first detection Identification of a precursor signal, detectable above the noise of natural climatic variability, of a significant change in a climate parameter and attribution of this change to an increase in atmospheric carbon dioxide concentration. The signal may be estimated by numeric modeling of the climate, and the noise can be estimated using instrumental data. For any modeled signal that is estimated, the corresponding noise can be estimated from observational data, and a signal-tonoise ratio can be calculated to provide a quantitative measure of detectability. flaring The burning of waste gases through a flare stack or other device before releasing them to the air. flow law In glaciology, a constitutive relation for the analysis of threedimensional deformation states of ice subjected to stress. fog Liquid particles less than 40 microns in diameter that are formed by condensation of vapor in air.

food chain A sequence of organisms, each of which uses the next lower member of the sequence as a food source. fossil fuel Any hydrocarbon deposit that can be burned for heat or power, such as petroleum, coal, and natural gas. fungi Molds, mildews, yeasts, mushrooms, and puffballs, a group of organisms that lack chlorophyll and therefore are not photosynthetic. They are usually nonmobile, filamentous, and multicellular.

G general circulation models Hydrodynamic models of the atmosphere on a grid or spectral resolution that determine the surface pressure and the vertical distributions of velocity, temperature, density, and water vapor as functions of time from the mass conservation and hydrostatic laws, the first law of thermodynamics, Newton's second law of motion, the equation of state, and the conservation law for water vapor. Abbreviated as GCM. Atmospheric general circulation models are abbreviated AGCM, while oceanic general circulation models are abbreviated OGCM. geomorphology The study of present-day landforms, including their classification, description, nature, origin, development, and relationships to underlying structures. Also the his- tory of geologic changes as recorded by these surface features. The term is sometimes restricted to features produced only by erosion and deposition. geosphere The solid mass (lithosphere) of the Earth as distinct from the atmosphere and hydrosphere or all three of these layers combined. geostrophic flow A type of movement where the Coriolis force balances exactly the horizontal pressure force. glacial maximum The position or time of the greatest advance of a glacier (e.g., the greatest equatorward advance of Pleistocene glaciation). glacial rebound The isostatic adjustment of previously glaciated areas after glacial retreat (e.g., the uplift of Scandinavia after the most recent glaciation). glacier

A mass of land ice that is formed by the cumulative recrystallization of firn. A glacier flows slowly (at present or in the past) from an accumulation area to an ablation area. Some well-known glaciers are: the Zermatt, Stechelberg, Grindelwald, Trient, Les Diablerets, and Rhone in Switzerland; the Nigards, Gaupne, Fanarak, Lom, and Bover in Norway; the Wright, Taylor, and Wilson Piedmont glaciers in Antarctica; the Bossons Glacier in France; the Emmons and Nisqually glaciers on Mt. Ranier, Washington; Grinnell glacier in Glacier National Park, Montana; the Dinwoody glacier in the Wind River Mountains and the Teton glacier in Teton National Park, both in Wyoming; and many glaciers in the Canadian Rockies. glacier flow (ice flow). The slow downward or outward movement of ice in a glacier caused by gravity. greenhouse effect A popular term used to describe the roles of water vapor, carbon dioxide, and other trace gases in keeping the Earth's surface warmer than it would be otherwise. These " radiatively active " gases are relatively transparent to incoming shortwave radiation, but are relatively opaque to outgoing longwave radiation. The latter radiation, which would otherwise escape to space, is trapped by these gases within the lower levels of the atmosphere. The subsequent reradiation of some of the energy back to the surface maintains surface temperatures higher than they would be if the gases were absent. There is concern that increasing concentrations of greenhouse gases, including carbon dioxide, methane, and manmade chlorofluorocarbons, may enhance the greenhouse effect and cause global warming. greenhouse gases Those gases, such as water vapor, carbon dioxide, tropospheric ozone, nitrous oxide, and methane, that are transparent to solar radiation but opaque to longwave

radiation. Their action is similar to that of glass in a greenhouse. Also see greenhouse effect and trace gas. Greenland Ice Sheet See ice sheet. grenz A soil horizon, which is frequently marked by a bed of clay, that results from a temporary halt in the accumulation of vegetal material. gross primary production The total amount or weight of organic matter created by photosynthesis over a defined time period (total product of photosynthesis). Abbreviated GPP. ground cover Plants grown to keep soil from eroding. grounding line The boundary between the area where an ice shelf or a glacier is floating on water and where it is in contact with the shore or underlying earth (grounded). groundwater The supply of fresh water found beneath the surface of the Earth (usually in aquifers) that often supplies wells and springs. growth water-use efficiency A measure at the individual plant level of how well plants use available water in growth. The units of dry matter synthesized are divided by the units of water lost. Gulf Stream meander A transient winding bend in the Gulf Stream. These bends intensify as the Gulf Stream merges into the North Atlantic and can break up into detached eddies at about 40 degrees S. gyres Major circular flow patterns in the oceans. The wind- driven eastward- and westward-flowing equatorial currents are blocked by the continents and rotate slowly in a clockwise direction in the North Atlantic and Pacific Oceans and in a

counter- clockwise direction in the South Atlantic, South Pacific, and Indian Oceans.

H Hadley cell A direct thermally-driven and zonally symmetric large- scale atmospheric circulation first proposed by George Hadley in 1735 as an explanation for the trade winds. It carries momentum, sensible heat, and potential heat from the tropics to the mid-latitudes (30 degrees). The poleward transport aloft is complemented by subsidence in the subtropical high pressure ridge and a surface return flow. The variability of this cell and the Walker cell is hypothesized to be a major factor in short-term climatic change. halocline In the oceans, a well-defined vertical gradient of salinity. heat flux (thermal flux) The amount of heat that is transferred across a surface of unit area in a unit of time. heat island effect A dome of elevated temperatures over an urban area caused by the heat absorbed by structures and pavement. herbivore An animal that feeds on plants. heterotrophs Organisms that break down and use organic matter. histosol Wet organic soils, such as peats and mucks. Holdridge life zone A climate category defined by three weighted climatic indexes, namely, mean annual heat, precipitation, and atmospheric moisture. Holocene The most recent epoch of the Quaternary period , covering approximately the last 10,000 years. humus Decomposed organic material.

hydrologic budget A quantitative accounting of all water volumes and their changes with time for a basin or area. hydrologic cycle The process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologic cycle is responsible for 25 to 30 percent of the mid-latitudes' heat transport from the equatorial to polar regions. hydrology The science dealing with the properties, distribution, and circulation of water. hydrosphere The aqueous envelope of the Earth, including the oceans, freshwater lakes, rivers, saline lakes and inland seas, soil moisture and vadose water, groundwaters, and atmospheric vapor. hydrostatic equation In the vector equation of motion, the form assumed by the vertical component when all Coriolis, earth-curvature, frictional, and vertical-acceleration terms are con- sidered negligible compared with those involving the vertical pressure force and the force of gravity. The error in applying the hydrostatic equation to the atmosphere for cyclonic-scale motions is less than 0.01%. In extreme situations, the strong vertical accelerations in thunderstorms and mountain waves can be 1% of gravity. hypsithermal period The period about 4000 to 8000 years ago when the Earth was apparently several degrees warmer than it is now. More rainfall occurred in most of the subtropical desert regions and less in the central midwest United States and Scandinavia. It is also called the altithermal period and can serve as a past

climate analog for predicting the regional pattern of climate change should the mean Earth surface temperature increase from an increase in atmospheric carbon dioxide concentration.

I ice age A glacial epoch or time of extensive glacial activity. Also, as Ice Age, which refers to the latest glacial epoch, the Pleistocene Epoch. ice and snow albedo The reflectivity of ice and snow-covered surfaces. The albedo of freshly fallen snow may be as much as 90%, while older snow may have values of 75% or less. The larger the areal extent of snow and ice cover, the higher the albedo value. The surface albedo will also increase as a function of the depth of snow cover up to 13 cm and be unaffected by increased snow cover after reaching that depth. ice and snow-albedo-temperature feedback Interactions that can be described as a theoretical concept of a feedback mechanism in which the interacting elements are the areal extent of polar ice and snow cover, the albedo of the polar region (dependent on areal extent of ice and snow), absorption of solar radiation (dependent on the albedo), temperature (dependent on the absorption of solar radiation) and the area of ice and snow cover (dependent on temperature). Less snowfall would mean more absorption of solar radiation, therefore a surface warming would occur. Climate modeling studies indicate an amplification effect (i.e., positive feedback) of the ice and snow-albedo feedback on increased surface air temperatures caused by increases in the atmospheric concentration of carbon dioxide. ice cover During the present time, the extent, especially the thickness, of glacier ice on a land surface. Also the same as ice concentration, which is the ratio of an area of sea ice to the total area of sea surface within some large geographic area. ice flow See glacier flow.

ice front The floating vertical cliff that forms the seaward face or edge of a glacier or an ice shelf that enters water. It can vary from 2 to 50 m in height. ice sheet (continental glacier) A glacier of considerable thickness and more than 50,000 sq km in area. It forms a continuous cover of ice and snow over a land surface. An ice sheet is not confined by the underlying topography but spreads outward in all directions. During the Pleistocene Epoch, ice sheets covered large parts of North America and northern Europe but they are now confined to polar regions (e.g., Greenland and Antarctica). ice shelf A sheet of very thick ice with a level or gently undulating surface. It is attached to the land on one side, but most of it is floating. On the seaward side, it is bounded by a steep cliff (ice front) 2 to 50 m or more above sea level. Ice shelves have formed along polar coasts (e.g., Antarctica and Greenland); they are very wide with some extending several hundreds of kilometers toward the sea from the coastline. They increase in size from annual snow accumulation and seaward extension of land glaciers. They decrease in size from warming, melting, and calving. infiltration (soil) Movement of water from the ground surface into the soil. infrared radiation Electromagnetic radiation lying in the wavelength interval from 0.7 micrometers to 1000 micrometersm. Its lower limit is bounded by visible radiation, and its upper limit by microwave radiation. Most of the energy emitted by the Earth and its atmosphere is at infrared wavelength. Infrared radiation is generated almost entirely by large-scale intramolecular processes. The tri-atomic gases, such as water vapor, carbon dioxide, and ozone, absorb infrared radiation and play important roles in the propagation of infra- red

radiation in the atmosphere. Abbreviated IR; also called "longwave radiation". insolation The solar radiation incident on a unit horizontal surface at the top of the atmosphere. It is sometimes referred to as solar irradiance. The latitudinal variation of insolation supplies the energy for the general circulation of the atmosphere. Insolation depends on the angle of incidence of the solar beam and on the solar constant. instantaneous transpiration efficiency A measure at the physiologic level of how well plants use available water in photosynthesis. The assimilation rate is divided by the transpiration rate; the moles of CO2 taken up are divided by the moles of water lost through transpiration in a unit of time. inversion An anomaly in the normal positive lapse rate; usually refers to a thermal inversion, in which temperature increases rather than decreases with height. irradiance The total radiant flux received on a unit area of a given real or imaginary surface. Also called the radiant flux density. isopynic A line on a chart that connects all points of equal or constant density. isostatic adjustment (isostatic compensation) The process whereby lateral transport at the Earth's surface from erosion or deposition is compensated for by movements in a subcrustal layer to maintain equilibrium among units of varying masses and densities. isotherm A line on a chart that connects all points of equal or constant temperature. isotope

One of two or more atoms that have the same atomic number (i.e., the same number of protons in their nuclei) but have different mass numbers.

K Krakatoa (Krakatau) Active volcano 2667 ft (813 m) high in West Indonesia. It forms an island between Java and Sumatra. Its eruption in 1883, which was one of the most violent in modern times, scattered debris and darkened skies over vast areas. Additional eruptions occurred in late 1927 and in the l960s.

L lapse rate The rapidity with which temperature decreases with altitude. The normal lapse rate is defined to be 3.6 degrees F per 1000 feet change in altitude. The dry adiabatic lapse rate is about 5.5 degrees F per 1000 feet, and the wet adiabatic lapse rate varies between 2 and 5 degrees F per 1000 feet. latent heat Energy transferred from the earth's surface to the atmosphere through the evaporation and condensation processes. Le Chatelier's principle When an external force is applied to an equilibrium system, the system adjusts to minimize the effect of the force. life zone A climatically-defined class that can be associated with regions of soil and biota with a high uniformity in species composition and environmental adaptation. See Holdridge life zone. lithosphere The component of the Earth's surface comprising the rock, soil, and sediments. It is a relatively passive component of the climate system, and its physical character- istics are treated as fixed elements in the determination of climate. litter Undecomposed plant residues on the soil surface. Little Ice Age A cold period that lasted from about A.D. 1550 to about A.D. 1850 in Europe, North America, and Asia. This period was marked by rapid expansion of mountain glaciers, especially in the Alps, Norway, Ireland, and Alaska. There were three maxima, beginning about 1650, about 1770, and 1850, each separated by slight warming intervals. loess

A buff-colored, wind-blown deposit of fine silt, which is frequently exposed in bluffs with steep faces. The thickness can range from 6 to 30 m. The loess of the USA and Europe is thought to be the fine materials first transported and deposited by the waters of melting ice sheets during the glacial period. It was later blown consider- able distances with, in some cases, deposition in lakes. The origin of Asiatic loess, however, is apparently wind-blown dust from central Asian deserts. longwave radiation The radiation emitted in the spectral wavelength greater than 4 micrometers corresponding to the radiation emitted from the Earth and atmosphere. It is sometimes referred to as terrestrial radiation or infrared radiation, although somewhat imprecisely.

M marsh A type of wetland that does not accumulate appreciable peat deposits and is dominated by herbacious vegetation. Marshes may be fresh- or saltwater, tidal or nontidal. mass balance The application of the principle of the conservation of matter. For example, the mass of a glacier is not destroyed or created; the mass of a glacier and all its constitutive components remains the same despite alterations in their physical states. The mass balance of a glacier is calculated with the input/output relationships of ice, firn, and snow, usually measured in water equivalent. Output includes all ablative processes of surface melting, basal melting, evaporation, wind deflation, calving, and internal melting. Input includes direct precipitation, avalanching, and the growth of superimposed ice. Mauna Loa An intermittently active volcano 13,680 ft (4,170 m) high in Hawaii. Last eruption was in 1984. Also see Mauna Loa record. Mauna Loa record The record of measurements of atmospheric carbon dioxide concentrations taken at the Mauna Loa Observatory, Mauna Loa, Hawaii, since March 1958. The Mauna Loa record is the longest reliable daily record of atmospheric carbon dioxide measurements in the world. Maunder minimum The period from 1654 to 1714 when it was believed that there were no sunspots. It is now thought that there were some sunspots during that time but less than the numbers counted after 1800. mean sea level

The average height of the sea surface, based upon hourly observation of the tide height on the open coast or in adjacent waters that have free access to the sea. In the United States, it is defined as the average height of the sea surface for all stages of the tide over a nineteen year period. Mean sea level, commonly abbreviated as MSL and referred to simply as sea level, serves as the reference surface for all altitudes in upper atmospheric studies. mesic environment A habitat with a moderate amount of water. mesoscale eddies (mode eddies) In the ocean, dense and irregularly-oval high- and lowpressure centers about 400 km in diameter. The intensities of currents in these centers are about 10 times greater than the local means. Milankovitch theory An astronomical theory formulated by the Yugoslav mathematician Milutin Milankovitch that associates climate change with fluctuations in the seasonal and geographic distribution of insolation determined by periodic variations of the Earth's eccentricity and obliquity and the longitude of the perihelion. mist Liquid particles 40 to 500 microns in diameter that are formed by condensation of vapor in air. modeling An investigative technique that uses a mathematical or physical representation of a system or theory that accounts for all or some of its known properties. Models are often used to test the effects of changes of system components on the overall performance of the system. monsoon A name for seasonal winds, first applied to the winds over the Arabian Sea that blow for six months from the northeast and for six months from the southwest. The term has been

extended to similar winds in other parts of the world (i.e., the prevailing west to northwest winds of summer in Europe have been called the European monsoon). The primary cause for these seasonal winds is the much greater annual variation of temperature over large land areas compared with neighboring ocean surfaces, causing an excess of pressure over the continents in winter and a deficit in summer, but other factors, such as topography of the land, also have an effect. The monsoons are strongest in the southern and eastern sides of Asia, but also occur along the coasts of tropical regions wherever the planetary circulation is not strong enough to inhibit them. The monsoon climate can be described as a long winter-spring dry season, which includes a cold season followed by a short hot season just preceding the rains; a summer and early autumn rainy season, which is generally very wet but may vary greatly from year to year; and a secondary warming immediately after the rainy season.

N natural selection The process of survival of the fittest by which organisms that adapt to their environment survive while those that do not adapt disappear. negative feedback An interaction that reduces or dampens the response of the system in which it is incorporated. net primary production The part of the gross primary production that remains stored in the producer organism (primarily green plants) after deducting the amount used during the process of respiration. Abbreviated NPP. nutrient Any substance assimilated by living things that promotes growth.

O ocean mixing Processes that involve rates of advection, upwelling/ downwelling, and eddy diffusion and that determine how rapidly excess atmospheric carbon dioxide can be taken up by the oceans. opacity The degree of obscuration of light; for example, a glass window has almost 0% opacity, whereas a concrete wall has 100% opacity. optical thickness (optical depth) In calculating the transfer of radiant energy, the mass of an absorbing or emitting material lying in a vertical column of unit cross-sectional area and extending between two specified levels. Also, the degree to which a cloud prevents light from passing through it; the optical thickness then depends on the physical constitution (crystals, drops, and/or droplets), the form, the concentration, and the vertical extent of the cloud. ozone A molecule made up of three atoms of oxygen. In the statosphere, it occurs naturally and it provides a protective layer shielding the Earth from ultraviolet radiation and subsequent harmful health effects on humans and the environment. In the troposphere, it is a chemical oxidant and major component of photochemical smog.

P paleosol An ancient soil or soil horizon that formed on the surface during the geologic past. paludification The expansion of a bog caused by the gradual rising of the water table as accumulation of peat impedes water drainage. palynology The science of reconstructing the past flora and past climate from pollen data obtained from lake and bog sediments. The fossil pollen record is a function of the regional flora and vegetation at a given time and location. particulate matter Very small pieces of solid or liquid matter, such as particles of soot, dust, aerosols, fumes, or mists. past climate analogs The reconstructing of past climates at a given locality from modern climatic conditions in a different elevation or latitudinal zone to infer past climatic conditions. pCO2 The partial pressure of CO2 in the atmosphere and the ocean. In the atmosphere, the partial pressure of CO2 is defined as the pressure the CO2 would exert if all other gases were removed. The sum of the partial pressure of all the atmospheric gases will equal the atmospheric pressure. The partial pressure of CO2 in the atmosphere is determined by the atmospheric CO2 concentration and atmospheric temperature. In the ocean, the pCO2 is determined by the amount of dissolved CO2 and H2CO3. It varies with alkalinity, latitude, depth, and temperature. Biological processes in the ocean also exert an influence on the pCO2 in the ocean. percolation

The movement of water downward and radially through the subsurface soil layers, usually continuing downward to the groundwater. permafrost Perennially frozen ground that occurs wherever the temperature remains below 0 degrees C for several years. phenology The study of periodic biological phenomena with relation to climate, particularly seasonal changes. These phenomena can be used to interpret local seasons and the climatic zones. photochemical smog Air pollution caused by chemical reactions among various substances and pollutants in the atmosphere. photoelectric Of or relating to the electrical effects of light, including the emission of electrons, the generation of a voltage, or a change in resistance. photosynthesis The manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll with sunlight as the energy source. Oxygen and water vapor are released in the process. Photosynthesis is dependent on favorable temperature and moisture conditions as well as on the atmospheric carbon dioxide concentration. Increased levels of carbon dioxide can increase net photosynthesis in many plants. phytoplankton That portion of the plankton community comprised of tiny plants (e.g., algae and diatoms). planetary albedo The fraction (approximately 30%) of incident solar radiation that is reflected by the earth-atmosphere system and returned to space, mostly by backscatter from clouds in the atmosphere. planetary boundary layer

The transition region between the turbulent surface layer and the normally nonturbulent free atmosphere. This region is about 1 km in thickness and is characterized by a welldeveloped mixing generated by frictional drag as the air masses move over the Earth's surface. This layer contains approximately 10% of the mass of the atmosphere. Also called the atmospheric boundary layer or frictional layer. plankton Passively floating or weakly motile aquatic plants ( phytoplankton) and animals (zooplankton ). Pleistocene The earlier of the two epochs of the Quaternary period, starting 2 to 3 million years before the present and ending about 10,000 years ago. It was a time of glacial activity. positive feedback An interaction that amplifies the response of the system in which it is incorporated. precipitation Any or all forms of liquid or solid water particles that fall from the atmosphere and reach the Earth's surface. It includes drizzle, rain, snow, snow pellets, snow grains, ice crystals, ice pellets, and hail. The ratio of precipitation to evaporation is the most important factor in the distribution of vegetation zones. Precipitation is also defined as a measure of the quantity, expressed in centimeters or milliliters of liquid water depth, of the water substance that has fallen at a given location in a specified amount of time. primary productivity See gross primary production and net primary production. primary succession The natural development of vegetation and soil on a site that had not previously borne vegetation (e.g., a sand dune or lava flow), which vegetation will be replaced by other, successive plant communities.

primitive equations The Eulerian equations of fluid motion in which the primary dependent variables are the velocity components of the fluid. In meteorology, they can be specialized to apply directly to the cylonic-scale motions. proxy climate indicators Dateable evidence of a biological or geological phenomenon whose condition, at least in part, is attributable to climatic conditions at the time of its formation. Proxy data are any material that provides an indirect measure of climate and include documentary evidence of crop yields, harvest dates, glacier movements, tree rings, varves, glaciers and snow lines, insect remains, pollen remains, marine microfauna, isotope measurements: 18O, in ice sheets, 18O, 2H, and 13C in tree rings; CaCO3 in sediments; and speleothems. There are three main problems in using proxy data: (1) dating, (2) lag and response time, and (3) meteorological interpretation. Tree rings, pollen deposits from varved lakes, and ice cores are the most promising proxy data sources for reconstructing the climate of the last five millennia because the dating are precise on an annual basis while other proxy data sources may only be precise to +/- 100 years. pycnocline In the ocean, a region where the water density increases rapidly with depth. pyrgeometer An instrument that measures radiation from the earth's surface into space.

Q Quaternary period The latest period of geologic time, covering the most- recent 2,000,000 years of the Earth's history. It is divided into two epochs: the Pleistocene - 2 million years ago to approximately 10,000 years ago - and the Holocene - the period from approximately 10,000 years ago to the present. The Quaternary period is the artificial division of time separating prehuman and human periods. It contains five ice ages and four interglacial ages, and temperature indicators seem to show sharp and abrupt changes by several degrees.

R radiant flux density The total flow of radiation received on a unit area of a given real or imaginary surface. Also called the irradiance. radiation balance The difference between the absorbed solar radiation and the net infrared radiation. Experimental data show that radiation from the earth's natural surfaces is rather close to the radiation from a black body at the corresponding temperature; the ratio of the observed values of radiation to black body radiation is generally 0.90 - 1.0. radiative-convective models Thermodynamic models that determine the equilibrium temperature distribution for an atmospheric column and the underlying surface, subject to prescribed solar radiation at the top of the atmosphere and prescribed atmospheric composition and surface albedo. Submodels for the transfer of solar and terrestrial radiation, the heat exchange between the earth's surface and atmosphere, the vertical redistribution of heat within the atmosphere, the atmospheric water vapor content and clouds are included in these one-dimensional models. Abbreviated as RCM. radiatively active gases Gases that absorb incoming solar radiation or outgoing infrared radiation, thus affecting the vertical temperature profile of the atmosphere. Most frequently being cited as being radiatively active gases are water vapor, CO2, methane, nitrous oxide, chlorofluorocarbons, and ozone. radiosonde A balloon-borne instrument for the simultaneous measurement and transmission of meteorological data up to a height of approximately 30,000 meters (100,000 feet). The height of each pressure level of the observation is computed from data received via radio signals.

recharge The process by which water is added to a reservoir or zone of saturation, often by runoff or percolation from the soil surface. reflectivity The ratio of the energy carried by a wave that is reflected from a surface to the energy of a wave incident on the surface. relative sea level The height of the boundary between sea and air as measured in relationship to a fixed reference point on land. reservoir Any natural or artificial holding area used to store, regulate, or control a substance. residence time The size of any specific reservoir or pool of mass (e.g., carbon) divided by the total flux of mass into or out of that pool. respiration A biochemical process by which living organisms take up oxygen from the environment and consume organic matter, releasing both carbon dioxide and heat. In plants, the organic matter in photosynthate produced during daylight hours. Revelle factor The ratio of the instantaneous fractional change in the partial pressure of CO2 (pCO2) exerted by seawater to the fractional change in total CO2 dissolved in the ocean waters. The buffer factor relates the partial pressure of CO2 in the ocean to the total ocean CO2 concentration at constant temperature, alkalinity and salinity. The Revelle factor is a useful parameter for examining the distribution of CO2 between the atmosphere and the ocean, and measures in part the amount of CO2 that can be dissolved in the mixed surface layer. rocketsonde

A rocket-borne instrument for measurement and transmission of upper-air meteorological data in the lower 76,000 meters (250,000 feet) of the atmosphere, especially that portion inaccessible to radiosonde techniques. runoff That part of precipitation, snowmelt, or irrigation water that flows from the land to streams or other surface waters.

S salinity The degree of salt in water. salt water intrusion The invasion of fresh, surface, or groundwater by salt water. seasonal variation The change in a set of meteorological parameters averaged over three months. Seasonal variation is the largest climatic variation, and temperature is the most fre- quently observed meteorological parameter. Often, monthly averaged data are grouped into seasons, according to the prescribed definition. sea surface temperature The temperature of the layer of seawater (approximately 0.5 m deep) nearest the atmosphere. sea surface temperature anomalies Temperature of emitted energy from the sea surface. SST anomaly = (SST - SST mean). secular carbon dioxide trend The fairly uniform and accelerating increase of carbon dioxide concentration in the atmosphere, as illustrated by the Mauna Loa record. The secular trend reflects the increase in global atmospheric carbon dioxide concentrations produced by combustion of fossil fuels, kilning of limestone, and possibly a net biospheric release of carbon dioxide resulting from deforestation. sensible heat The excess radiative energy that has passed from the Earth's surface to the atmosphere through advection, conduction, and convection processes. shortwave radiation The radiation received from the sun and emitted in the spectral wavelengths less than 4 ?m. It is also called solar radiation. signal-to-noise ratio

A quantitative measure of the statistical detectability of a signal, expressed as a ratio of the magnitude of the signal relative to the variability. For first detection of a CO2induced climate change, the model signal is the mean change or anomaly in some climatic variable, usually surface air temperature, attributed by a numerical model to increased concentrations of carbon dioxide. Observed noise is the standard deviation or natural variability computed from observations of that variable and adjusted for sample size, autocorrelation, and time averaging. silviculture Management of forest land for timber. smog Air pollution associated with oxidants. smoke Particles suspended in air after incomplete combustion of materials. soil carbon A major component of the terrestrial biosphere pool in the carbon cycle. Organic soil carbon estimates, rather than total soil carbon, are generally quoted. The amount of carbon in the soil is a function of historical vegetative cover and productivity, which in turn is dependent upon climatic variables. solar constant The rate at which solar energy is received just outside the Earth's atmosphere on a surface that is normal to the incident radiation and at the mean distance of the Earth from the sun. The current value is 0.140 watt/cm2. solar cycle The periodic change in sunspot numbers. It is the interval between successive minima and is about 11.1 years. Southern Oscillation A large-scale atmospheric and hydrospheric fluctuation centered in the equatorial Pacific Ocean. It exhibits a nearly

annual pressure anomaly, alternatively high over the Indian Ocean and high over the South Pacific. Its period is slightly variable, averaging 2.33 years. The variation in pressure is accompanied by variations in wind strengths, ocean currents, sea-surface temperatures, and precipitation in the surrounding areas. El Nino occurrences are associated with the phenomenon. Southern Oscillation Index An indicator based on the pressure gradient between the quasi-stationary low pressure region and the center of a subtropical high pressure cell. A positive index corresponds to an anomalously high pressure difference between the two centers of action. statistical-dynamical models Computer programs that calculate simplified climate models based on versions of the conservation equations that have been averaged over longitude, with the effects of the synoptic eddies parameterized statistically in the meridional plane. steric height The mean dynamic depth (or height) of the ocean for the month minus the annual mean dynamic depth for the same isobaric reference level. stoma, plant stomata A minute pore in the epidermis of plant leaves or stems. Stoma, which are bordered by guard cells that regulate the size of the opening, function in gas exchange between the plant and the external environment. The stomatal apparatus or stomate consists of the stoma plus guard cells. stratification Separating into layers. stratosphere The region of the upper atmosphere extending from the tropopause (8 to 15 km altitude) to about 50 km. The thermal structure is determined by its radiation balance and is generally very stable with low humidity.

Suess effect The relative change in the 14C/C or 13C/C ratio of any carbon pool or reservoir caused by the addition of fossil- fuel CO2 to the atmosphere. Fossil fuels are devoid of 14C because of the radioactive decay of 14C to 14N during long underground storage and are depleted in 13C because of isotopic fractionation eons ago during photosynthesis by the plants that were the precursors of the fossil fuels. Carbon dioxide produced by the combustion of fossil fuels is thus virtually free of 14C and depleted in 13C. The term Suess effect originally referred to the dilution of the 14C/C ratio in atmospheric CO2 by the admixture of fossil-fuel produced CO2, but the definition has been extended to both the 14C and 13C ratios in any pool or reservoir of the carbon cycle resulting from human disturbances. sunspot A relatively dark, sharply defined region on the solar disk, marked by an umbra approximately 2000K cooler than the effective photospheric temperature, surrounded by a less dark but also sharply bounded penumbra. The average spot diameter is about 3700 km, but can range up to 245,000 km. Most sunspots are found in groups of two or more, but they can occur singly. Sunspots are cyclic, with a period of approximately 11 years. The quantitative description of sunspot activity is called the Wolf sunspot number, denoted R. The Wolf sunspot number is also referred to as Wolfer sunspot number, Zurich relative sunspot number, or relative sunspot number. surface air temperature The temperature of the air near the surface of the Earth, usually determined by a thermometer in an instrument shelter about 2 m above the ground. The true daily mean, obtained from a thermograph, is approximated by the mean of 24 hourly readings and may differ by 1.0 degrees C from the

average based on minimum and maximum readings. The global average surface air temperature is 15 degrees C. surface albedo The fraction of solar radiation incident on the Earth's surface that is reflected by it. Reflectivity varies with ground cover, and during the winter months it varies greatly with the amount of snow cover (depth and areal extent). Roughness of terrain, moisture content, solar angle, and angular and spectral distribution of ground- level irradiations are other factors affecting surface albedo. surface water All water naturally open to the atmosphere. swamp A type of wetland that is dominated by woody vegetation and does not accumulate appreciable peat deposits; it may be fresh- or saltwater, and tidal or nontidal.

T tephra Any rock material produced by a volcano. terrestrial radiation The total infrared radiation emitted by the Earth and its atmosphere in the temperature range of approximately 200300K. Because the Earth is nearly a perfect radiator, the radiation from its surface varies as the fourth power of the surface's absolute temperature. Terrestrial radiation provides a major part of the potential energy changes necessary to drive the atmospheric wind system and is responsible for maintaining the surface air temperature within limits for livability. thermocline A transition layer of water in the ocean, with a steeper vertical temperature gradient than that found in the layers of ocean above and below. The permanent ther- mocline separates the warm mixed surface layer of the ocean from the cold deep ocean water, and is found between 100- and 1000m depths. The thermocline first appears at the 55 - 60 degree N and S latitudes, where it forms a horizontal separation between temperate and polar waters. The thermocline reaches its maximum depth at mid-latitudes and is shallowest at the equator and at its northern and southern limits. The thermocline is stably stratified, and transfer of water and carbon dioxide across this zone occurs very slowly. Thus, the thermocline acts as a barrier to the downward mixing of carbon dioxide. thermohaline Refers to the combined effects of temperature and salinity that contribute to density variations in the oceans. tidal marsh

Low, flat marshlands traversed by channels and tidal hollows and subject to tidal innundation; normally, the only vegetation present are salt-tolerant bushes and grasses. trace gas A minor constituent of the atmosphere. The most important trace gases contributing to the greenhouse effect are water vapor, carbon dioxide, ozone, methane, ammonia, nitric acid, nitrous oxide, ethylene, sulfur dioxide, nitric oxide, dichlorofluoromethane or Freon 12, trichlorofluoromethane or Freon 11, methyl chloride, carbon monoxide, and carbon tetrachloride. transient tracers Chemical elements (often radioactive) or compounds that have finite lifetimes. Atmospheric testing of nuclear weapons from the mid-1950s to the early 1960s released large quantities of radionuclides to the atmosphere. Atmosphereocean exchange processes have transferred some of these elements to the oceans. Studying the behavior and distribution of these specific isotopes and other chemical tracers in the ocean will provide information on: residence times of the water and its dissolved components in gyres, basins, etc.; the mode and rate of formation and the subsequent spreading rates of specific water types, such as the polar water of the Norwegian and Greenland Seas; deepocean circulation and ocean- mixing processes, such as advection and upwelling; and the flux of anthropogenic carbon dioxide into the ocean through its correlation with several different transient tracers. transpiration The process in plants by which water is taken up by the roots and released as water vapor by the leaves. The term can also be applied to the quantity of water thus dissipated. tree rings Annual growth increments of trees that indicate, among other factors, the climatic conditions that enhance or limit growth.

Tree ring widths and indexes have been used to search for solar-terrestrial relationships and climatic cycles and to reconstruct past climates. See also dendroclimatology and dendrochronology. trophic level A segment of the food chain in which all organisms obtain food and energy in, basically, the same manner (e.g., photosynthesis, herbivory, or carnivory) and in which all organisms are the same number of links from the photosynthetic segment. tropopause The boundary between the troposphere and the stratosphere (about 8 km in polar regions and about 15 km in tropical regions), usually characterized by an abrupt change of lapse rate. The regions above the troposphere have increased atmospheric stability than those below. The tropopause marks the vertical limit of most clouds and storms. troposphere The inner layer of the atmosphere below about 15 km, within which there is normally a steady decrease of temperature with increasing altitude. Nearly all clouds form and weather conditions manifest themselves within this region, and its thermal structure is caused primarily by the heating of the Earth's surface by solar radiation, followed by heat transfer by turbulent mixing and convection. tundra A type of ecosystem dominated by lichens, mosses, grasses, and woody plants. It is found at high latitudes (arctic tundra) and high altitudes (alpine tundra). Arctic tundra is underlain by permafrost and usually very wet. turnover rate The fraction of the total amount of mass (e.g., carbon) in a given pool or reservoir that is released from or that enters the pool in a given length of time. The turnover rate of carbon is often expressed as GtC/year.

U upwelling The vertical motion of water in the ocean by which subsurface water of lower temperature and greater density moves toward the surface of the ocean. Upwelling occurs most commonly among the western coastlines of continents, but may occur anywhere in the ocean. Upwelling results when winds blowing nearly parallel to a continental coastline transport the light surface water away from the coast. Subsurface water of greater density and lower temperature replaces the surface water, and exerts a considerable influence on the weather of coastal regions. Carbon dioxide is transferred to the atmosphere in regions of upwelling. This is especially important in the Pacific equatorial regions, where 1 - 2 GtC/year may be released to the atmosphere. Upwelling also results in increased ocean productivity by transporting nutrient-rich waters to the surface layer of the ocean.

V vapor The gaseous phase of substances that are liquid or solid at atmospheric pressure (e.g., steam). varve A layer of sediment deposited in lakes during one year. Each layer consists of two parts, which are deposited at different seasons and which differ in color and texture; thus, the layers can be counted and measured. In a complete series, the number of layers gives the date on which the ground was vacated by the retreating ice.

W Walker cell A zonal circulation of the atmosphere confined to equatorial regions and driven principally by the oceanic temperature gradient. In the Pacific, air flows westward from the colder, eastern area to the warm, western ocean, where it acquires warmth and moisture and subsequently rises. A return flow aloft and subsidence over the eastern ocean complete the cell. water stress effect The closing of the stomata by a plant in response to excessive water loss through transpiration or in response to drought conditions. The stomatal closing reduces CO2 uptake as well as water loss, thus decreasing the photosynthetic rate. However, under conditions of elevated CO2 concentration, the CO2 gradient between the atmosphere and the leaf is higher than under ambient conditions, and CO2 can pass through partially closed stomates at a rate similar to that under conditions of lower CO2 and open stomates. The humidity gradient remains the same at higher CO2, and transpiration is impeded. The net result is improved wateruse efficiency by some plants. water table The level of groundwater. water-use efficiency A measure of the amount of water used by plants per unit of plant material produced. The term can be applied at the leaf, whole-plant, and ecosystem levels. At the leaf level, it is more precisely referred to as the instantaneous transpiration efficiency, the CO2 assimilation rate (photosynthesis) divided by the transpiration rate (the moles of CO2 taken up divided by the moles of water lost through transpiration in a unit of time per unit leaf area). At the whole-plant level, it is more precisely referred to as the growth water-use efficiency, the units of dry matter

synthesized divided by the units of water lost. At the ecosystem level, it is more precisely referred to as the crop water-use efficiency, the grams of dry weight gained by plants during the growing season per unit land area divided by the millimeters of water lost (including evaporation directly from the soil). water vapor Water present in the atmosphere in gaseous form; the source of all forms of condensation and precipitation. Water vapor, clouds, and carbon dioxide are the main atmospheric components in the exchange of terrestrial radiation in the troposphere, serving as a regulator of planetary temperatures via the greenhouse effect. Approximately 50 percent of the atmosphere's moisture lies within about 1.84 km of the earth's surface, and only a minute fraction of the total occurs above the tropopause. water vapor feedback A process in which an increase in the amount of water vapor increases the atmosphere's absorption of longwave radiation, thereby contributing to a warming of the atmosphere. Warming, in turn, may result in increased evaporation and an increase in the initial water vapor anomaly. This feedback, along with carbon dioxide, is responsible for the greenhouse effect and operates virtually continuously in the atmosphere. weather The instantaneous state of the global atmosphere-oceancryosphere system. West Antarctic Ice Sheet See ice sheet. wetlands An area that is regularly saturated by surface water or groundwater and subsequently is characterized by a prevalence of vegetation that is adapted for life in saturatedsoil conditions.

Z zonally-averaged models Statistical-dynamical or energy-balance models in which only the latitudinally averaged quantities are determined and the effects of the longitudinally varying transports are determined parametrically. Abbreviated as ZAM. zooplankton That portion of the plankton community comprised of tiny aquatic animals eaten by fish.

A/C- An abbreviation for air conditioner or air conditioning. A/C Condenser- The outside fan unit of the Air Conditioning system. It removes the heat from the freon gas and "turns" the gas back into a liquid and pumps the liquid back to the coil in the furnace. A/C Disconnect- The main electrical ON-OFF switch near the A/C Condenser. Aerator- The round screened screw-on tip of a sink spout. It mixes water and air for a smooth flow. Aggregate- A mixture of sand and stone and a major component of concrete. Air space - The area between insulation facing and interior of exterior wall coverings. Normally a 1" air gap. Allowance(s) - A sum of money set aside in the construction contract for items which have not been selected and specified in the construction contract. For example, selection of tile as a flooring may require an allowance for an underlayment material, or an electrical allowance which sets aside an amount of money to be spent on electrical fixtures. Amortization - A payment plan by which a loan is reduced through monthly payments of principal and interest. Anchor bolts- Bolts to secure a wooden sill plate to concrete , or masonry floor or wall. Annual Percentage Rate (APR)- Annual cost of credit over the life of a loan, including interest, service charges, points, loan fees, mortgage insurance, and other items. Appraisal An expert valuation of property. Apron- A trim board that is installed beneath a window sill

Architect - One who has completed a course of study in building and design, and is licensed by the state as an architect. One who draws up plans. Area wells- Corrugated metal or concrete barrier walls installed around a basement window to hold back the earth Assessment - A tax levied on a property, or a value placed on the worth of a property. Assumption - Allows a buyer to assume responsibility for an existing loan instead of getting a new loan. Astragal- A molding, attached to one of a pair of swinging double doors, against which the other door strikes. Attic access- An opening that is placed in the drywalled ceiling of a home providing access to the attic. Attic Ventilators- In houses, screened openings provided to ventilate an attic space.

Back Charge- Billings for work performed or costs incurred by one party that, in accordance with the agreement, should have been performed or incurred by the party to whom billed. Owners bill back charges to general contractors, and general contractors bill back charges to subcontractors. Examples of back charges include charges for cleanup work or to repair something damaged by another subcontractor, such as a tub chip or broken window. Backfill- The replacement of excavated earth into a trench around or against a basement /crawl space foundationwall. Backing- Frame lumber installed between the wall studs to give additional support for drywall or an interior trim related item, such as handrail brackets, cabinets, and towel bars. In this way, items are screwed and mounted into solid wood rather than weak drywall that may allow the item to break loose from the wall. Carpet backing holds the pile fabric in place. Backout- Work the framing contractor does after the mechanical subcontractors (Heating-Plumbing-Electrical) finish their phase of work at the Rough (before insulation) stage to get the home ready for a municipal frame inspection. Generally, the framing contractor repairs anything disturbed by others and completes all framing necessary to pass a Rough Frame Inspection. Ballast- A transformer that steps up the voltage in a florescent lamp. Balloon - A loan that has a series of monthly payments with the remaining balance due in a large lump sum payment at the end. Balloon framed wall- Framed walls (generally over 10' tall) that run the entire vertical length from the floor sill plate to the roof. This is done to eliminate the need for a gable end truss. Balusters- Vertical members in a railing used between a top rail and bottom rail or the stair treads. Sometimes referred to as 'pickets' or 'spindles'. Balustrade- The rail, posts and vertical balusters along the edge of a stairway or elevated walkway. Barge- Horizontal beam rafter that supports shorter rafters.

Barge board- A decorative board covering the projecting rafter (fly rafter) of the gable end. At the cornice, this member is a fascia board. Base or baseboard- A trim board placed against the wall around the room next to the floor. Basement window inserts- The window frame and glass unit that is installed in the window buck. Base shoe- Molding used next to the floor on interior base board. Sometimes called a carpet strip. Bat - A half-brick. Batt - A section of fiber-glass or rock-wool insulation measuring 15 or 23 inches wide by four to eight feet long and various thickness'. Sometimes "faced" (meaning to have a paper covering on one side) or "unfaced" (without paper). Batten- Narrow strips of wood used to cover joints or as decorative vertical members over plywood or wide boards. Bay window- Any window space projecting outward from the walls of a building, either square or polygonal in plan. Beam- A structural member transversely supporting a load. A structural member carrying building loads (weight) from one support to another. Sometimes called a "girder". Bearing partition- A partition that supports any vertical load in addition to its own weight. Bearing point- A point where a bearing or structural weight is concentrated and transferred to the foundation Bearing wall- A wall that supports any vertical load in addition to its own weight. Bearing header- (a) A beam placed perpendicular to joists and to which joists are nailed in framing for a chimney, stairway, or other opening. (b) A

wood lintel. (c) The horizontal structural member over an opening (for example over a door or window). Bedrock- A subsurface layer of earth that is suitable to support a structure. Bid- A formal offer by a contractor, in accordance with specifications for a project, to do all or a phase of the work at a certain price in accordance with the terms and conditions stated in the offer. Bid bond- A bond issued by a surety on behalf of a contractor that provides assurance to the recipient of the contractor's bid that, if the bid is accepted, the contractor will execute a contract and provide a performance bond. Under the bond, the surety is obligated to pay the recipient of the bid the difference between the contractor's bid and the bid of the next lowest responsible bidder if the bid is accepted and the contractor fails to execute a contract or to provide a performance bond. Bid security Funds or a bid bond submitted with a bid as a guarantee to the recipient of the bid that the contractor, if awarded the contract, will execute the contract in accordance with the bidding requirements of the contract documents. Bid shopping- A practice by which contractors, both before and after their bids are submitted, attempt to obtain prices from potential subcontractors and material suppliers that are lower than the contractors' original estimates on which their bids are based, or after a contract is awarded, seek to induce subcontractors to reduce the subcontract price included in the bid. Bidding requirements- The procedures and conditions for the submission of bids. The requirements are included ion documents, such as the notice to bidders, advertisements for bids, instructions to bidders, invitations to bid, and sample bid forms. Bifold door- Doors that are hinged in the middle for opening in a smaller area than standard swing doors. Often used for closet doors. Binder- A receipt for a deposit to secure the right to purchase a home at an agreed terms by a buyer and seller. Bipass doors- Doors that slide by each other and commonly used as closet doors.

Blankets- Fiber-glass or rock-wool insulation that comes in long rolls 15 or 23 inches wide. Blocked (door blocking)- Wood shims used between the door frame and the vertical structural wall framing members. Blocked (rafters)- Short "2 by 4's" used to keep rafters from twisting, and installed at the ends and at mid-span. Blocking- Small wood pieces to brace framing members or to provide a nailing base for gypsum board or paneling. Block out- To install a box or barrier within a foundation wall to prevent the concrete from entering an area. For example, foundation walls are sometimes "blocked" in order for mechanical pipes to pass through the wall, to install a crawl space door, and to depress the concrete at a garage door location. Blow insulation- Fiber insulation in loose form and used to insulate attics and existing walls where framing members are not exposed. Blue print(s) - A type of copying method often used for architectural drawings. Usually used to describe the drawing of a structure which is prepared by an architect or designer for the purpose of design and planning, estimating, securing permits and actual construction. Blue stake- Another phrase for Utility Notification. This is when a utility company (telephone, gas, electric, cable TV, sewer and water, etc) comes to the job site and locates and spray paints the ground and/or installs little flags to show where their service is located underground. Board foot- A unit of measure for lumber equal to 1 inch thick by 12 inches wide by 12 inches long. Examples: 1" x 12" x 16' = 16 board feet, 2" x 12" x 16' = 32 board feet Bond or bonding - An amount of money (usually $5,000-$10,000) which must be on deposit with a governmental agency in order to secure a contractor's license. The bond may be used to pay for the unpaid bills or disputed work of the contractor. Not to be confused with a 'performance bond'. Such bonds are rarely used in residential construction, they are an insurance policy which guarantees proper completion of a project.

Boom- A truck used to hoist heavy material up and into place. To put trusses on a home or to set a heavy beam into place. Bottom chord - The lower or bottom horizontal member of a truss. Bottom plate- The "2 by 4's or 6's" that lay on the subfloor upon which the vertical studs are installed. Also called the 'sole plate'. Brace- An inclined piece of framing lumber applied to wall or floor to strengthen the structure. Often used on walls as temporary bracing until framing has been completed. Breaker panel- The electrical box that distributes electric power entering the home to each branch circuit (each plug and switch) and composed of circuit breakers. Brick ledge- Part of the foundation wall where brick (veneer) will rest. Brick lintel- The metal angle iron that brick rests on, especially above a window, door, or other opening. Brick mold-Trim used around an exterior door jamb that siding butts to. Brick tie- A small, corrugated metal strip @ 1" X 6"- 8" long nailed to wall sheeting or studs. They are inserted into the grout mortar joint of the veneer brick, and holds the veneer wall to the sheeted wall behind it. Brick veneer- A vertical facing of brick laid against and fastened to sheathing of a framed wall or tile wall construction. Bridging- Small wood or metal members that are inserted in a diagonal position between the floor joists or rafters at mid-span for the purpose of bracing the joists/rafters & spreading the load. Buck- Often used in reference to rough frame opening members. Door bucks used in reference to metal door frame. See Window Bucks Builder's Risk Insurance- Insurance coverage on a construction project during construction, including extended coverage that may be added for the contract for the customer's protections.

Building codes- Community ordinances governing the manner in which a home may be constructed or modified. Building insurance- Insurance covering the structure of the building. Building paper- A general term for papers, felts, and similar sheet materials used in buildings without reference to their properties or uses. Generally comes in long rolls. Built-up roof- A roofing composed of three to five layers of asphalt felt laminated with coal tar, pitch, or asphalt. The top is finished with crushed slag or gravel. Generally used on flat or low-pitched roofs. Bull nose (drywall)- Rounded drywall corners. Bundle - A package of shingles. Normally, there are 3 bundles per square and 27 shingles per bundle. Butt edge- The lower edge of the shingle tabs. Butt hinge- The most common type. One leaf attaches to the door's edge, the other to its jamb. Butt joint- The junction where the ends of two timbers meet, and also where sheets of drywall meet on the 4 foot edge. To place materials end-to-end or end-to-edge without overlapping. Buy down- A subsidy (usually paid by a builder or developer) to reduce monthly payments on a mortgage. By fold door- Doors that are hinged in the middle for opening in a smaller area than standard swing doors. Often used for closet doors. By pass doors- Doors that slide by each other and commonly used as closet doors.

CO- An abbreviation for "Certificate of Occupancy". This certificate is issued by the local municipality and is required before anyone can occupy and live within the home. It is issued only after the local municipality has made all inspections and all monies and fees have been paid. Caisson- A 10" or 12" diameter hole drilled into the earth and embedded into bedrock 3 - 4 feet. The structural support for a type of foundation wall, porch, patio, monopost, or other structure. Two or more "sticks" of reinforcing bars (rebar) are inserted into and run the full length of the hole and concrete is poured into the caisson hole Cantilever- An overhang. Where one floor extends beyond and over a foundation wall. For example at a fireplace location or bay window cantilever. Normally, not extending over 2 feet. Cantilevered void- Foundation void material used in unusually expansive soils conditions. This void is "trapezoid" shaped and has vertical sides of 6" and 4" respectively. Cap- The upper member of a column, pilaster, door cornice, molding, or fireplace. Cap flashing- The portion of the flashing attached to a vertical surface to prevent water from migrating behind the base flashing. Capital- The principal part of a loan, i.e. the original amount borrowed. Capital and interest- A repayment loan and the most conventional form of home loan. The borrower pays an amount each month to cover the amount borrowed (or capital or principal) plus the interest charged on capital. Capped rate- The mortgage interest rate will not exceed a specified value during a certain period of time, but it will fluctuate up and down below that level. Casement- Frames of wood or metal enclosing part (or all) of a window sash. May be opened by means of hinges affixed to the vertical edges. Casement Window- A window with hinges on one of the vertical sides and swings open like a normal door

Casing- Wood trim molding installed around a door or window opening. Caulking- (1) A flexible material used to seal a gap between two surfaces e.g. between pieces of siding or the corners in tub walls. (2) To fill a joint with mastic or asphalt plastic cement to prevent leaks. CCA (Chromated Copper Arsenate)- A pesticide that is forced into wood under high pressure to protect it from termites, other wood boring insects, and decay caused by fungus Celotex ™- Black fibrous board that is used as exterior sheething. Ceiling joist- One of a series of parallel framing members used to support ceiling loads and supported in turn by larger beams, girders or bearing walls. Also called roof joists. Cement- The gray powder that is the "glue" in concrete. Portland cement. Also, any adhesive. Ceramic tile- A man-made or machine-made clay tile used to finish a floor or wall. Generally used in bathtub and shower enclosures and on counter tops. CFM (cubic feet per minute)- A rating that expresses the amount of air a blower or fan can move. The volume of air (measured in cubic feet) that can pass through an opening in one minute. Chair rail- Interior trim material installed about 3-4 feet up the wall, horizontally. Chalk line- A line made by snapping a taut string or cord dusted with chalk. Used for alignment purposes. Change order- A written document which modifies the plans and specifications and/or the price of the construction Contract. Chase- A framed enclosed space around a flue pipe or a channel in a wall, or through a ceiling for something to lie in or pass through. Chink- To install fiberglass insulation around all exterior door and window frames, wall corners, and small gaps in the exterior wall.

Chip Board- A manufactured wood panel made out of 1"- 2" wood chips and glue. Often used as a substitute for plywood in the exterior wall and roof sheathing. Also called OSB (Oriented Strand Board) or wafer board. Circuit- The path of electrical flow from a power source through an outlet and back to ground. Circuit Breaker- A device which looks like a switch and is usually located inside the electrical breaker panel or circuit breaker box. It is designed to (1) shut of the power to portions or all of the house and (2) to limit the amount of power flowing through a circuit (measured in amperes). 110 volt household circuits require a fuse or circuit breaker with a rating of 15 or a maximum of 20 amps. 220 volt circuits may be designed for higher amperage loads e.g. a hot water heater may be designed for a 30 amp load and would therefore need a 30 amp fuse or breaker. Class "A"- Optimum fire rating issued by Underwriter's Laboratories on roofing. The building codes in some areas require this type of roofing for fire safety. Class "C"- Minimum fire rating issued by the Underwriters' Laboratories for roofing materials. Clean out- An opening providing access to a drain line. Closed with a threaded plug. Clip ties- Sharp, cut metal wires that protrude out of a concrete foundation wall (that at one time held the foundation form panels in place). Cold air return- The ductwork (and related grills) that carries room air back to the furnace for re-heating. Collar- Preformed flange placed over a vent pipe to seal the roofing above the vent pipe opening. Also called a vent sleeve. Collar beam- Nominal 1- or 2-inch-thick members connecting opposite roof rafters. They serve to stiffen the roof structure. Column- A vertical structural compression member which supports loads.

Combustion air- The duct work installed to bring fresh, outside air to the furnace and/or hot water heater. Normally 2 separate supplies of air are brought in: One high and One low. Combustion chamber- The part of a boiler, furnace or woodstove where the burn occurs; normally lined with firebrick or molded or sprayed insulation. Compression web- A member of a truss system which connects the bottom and top chords and which provides downward support. Compressor- A mechanical device that pressurizes a gas in order to turn it into a liquid, thereby allowing heat to be removed or added. A compressor is the main component of conventional heat pumps and air conditioners. In an air conditioning system, the compressor normally sits outside and has a large fan (to remove heat). Concrete- The mixture of Portland cement, sand, gravel, and water. Used to make garage and basement floors, sidewalks, patios, foundation walls, etc. It is commonly reinforced with steel rods (rebar) or wire screening (mesh). Concrete block - A hollow concrete 'brick' often 8" x 8" x 16" in size. Concrete board - A panel made out of concrete and fiberglass usually used as a tile backing material. Condensation- Beads or drops of water (and frequently frost in extremely cold weather) that accumulate on the inside of the exterior covering of a building. Use of louvers or attic ventilators will reduce moisture condensation in attics. A vapor barrier under the gypsum lath or dry wall on exposed walls will reduce condensation. Condensing unit - The outdoor component of a cooling system. It includes a compressor and condensing coil designed to give off heat. Conditions, Convenants, and Restrictions (CC and Rs) - The standards that define how a property may be used and the protections the developer makes for the benefit of all owners in a subdivision. Conduction- The direct transfer of heat energy through a material.

Conductivity- The rate at which heat is transmitted through a material. Conduit, electrical- A pipe, usually metal, in which wire is installed. Construction Contract - A legal document which specifies the what-whenwhere-how-how much and by whom in a construction project. A good construction contract will include: 1. The contractors registration number. A statement of work quality such as 'Standard Practices of the 2. Trades' or 'according to Manufacturers Specifications'. 3. A set of Blue Prints or Plans 4. A construction timetable including starting and completion dates. 5. A set of Specifications 6. A Fixed Price for the work, or a Time and Materials formula. 7. A Payment Schedule. 8. Any Allowances. 9. A clause which outlines how any disputes will be resolved. 10. A written Warrantee. Construction drywall- A type of construction in which the interior wall finish is applied in a dry condition, generally in the form of sheet materials or wood paneling as contrasted to plaster. Construction, frame- A type of construction in which the structural components are wood or depend upon a wood frame for support. Continuity tester- A device that tells whether a circuit is capable of carrying electricity. Contractor- A company licensed to perform certain types of construction activities. In most states, the generals contractor's license and some specialty contractor's licenses don't require of compliance with bonding, workmen's compensation and similar regulations. Some of the specialty contractor licenses involve extensive training, testing and/or insurance requirements. There are various types of contractors: · General contractor - responsible for the execution, supervision and

overall coordination of a project and may also perform some of the individual construction tasks. Most general contractors are not licensed to perform all specialty trades and must hire specialty contractors for such tasks, e.g. electrical, plumbing. · Remodeling contractor - a general contractor who specializes in remodeling work. · Specialty contractor - licensed to perform a specialty task e.g. electrical, side sewer, asbestos abatement. · Sub contractor - a general or specialty contractor who works for another general contractor. Control joint- Tooled, straight grooves made on concrete floors to "control" where the concrete should crack Convection- Currents created by heating air, which then rises and pulls cooler air behind it. Also see radiation. Conventional loan A mortgage loan not insured by a government agency (such as FHA or VA) Convertibility The ability to change a loan from an adjustable rate schedule to a fixed rate schedule. Cooling load- The amount of cooling required to keep a building at a specified temperature during the summer, usually 78° F, regardless of outside temperature. Coped- Removing the top and bottom flange of the end(s) of a metal Ibeam. This is done to permit it to fit within, and bolted to, the web of another I-beam in a "T" arrangement Coped joint- Cutting and fitting woodwork to an irregular surface. Corbel- The triangular, decorative and supporting member that holds a mantel or horizontal shelf. Corner bead- A strip of formed sheet metal placed on outside corners of drywall before applying drywall 'mud'.

Corner boards- Used as trim for the external corners of a house or other frame structure against which the ends of the siding are finished. Corner braces- Diagonal braces at the corners of the framed structure designed to stiffen and strengthen the wall. Cornice- Overhang of a pitched roof , usually consisting of a fascia board, a soffit and appropriate trim moldings. Counter flashing- A metal flashing usually used on chimneys at the roofline to cover shingle flashing and used to prevent moisture entry. Counterfort- A foundation wall section that strengthens (and generally perpendicular to) a long section of foundation wall Course- A row of shingles or roll roofing running the length of the roof. Parallel layers of building materials such as bricks, or siding laid up horizontally. Cove molding- A molding with a concave face used as trim or to finish interior corners. Crawl space- A shallow space below the living quarters of a house, normally enclosed by the foundation wall and having a dirt floor. Credit rating- A report ordered by a lender from a credit agency to determine a borrower's credit habits. Cricket- A second roof built on top of the primary roof to increase the slope of the roof or valley. A saddle-shaped, peaked construction connecting a sloping roof with a chimney. Designed to encourage water drainage away from the chimney joint. Cripple- Short vertical "2 by 4's or 6's" frame lumber installed above a window or door. Cross bridging- Diagonal bracing between adjacent floor joists, placed near the center of the joist span to prevent joists from twisting. Cross Tee- Short metal "T" beam used in suspended ceiling systems to bridge the spaces between the main beams.

Crown molding- A molding used on cornice or wherever an interior angle is to be covered, especially at the roof and wall corner. Culvert- Round, corrugated drain pipe (normally 15" or 18" in diameter) that is installed beneath a driveway and parallel to and near the street. Cupping- A type of warping that causes boards to curl up at their edges. Curb- The short elevation of an exterior wall above the deck of a roof. Normally a 2 by 6 box (on the roof) on which a skylight is attached. Curb stop- Normally a cast iron pipe with a lid (@ 5" in diameter) that is placed vertically into the ground, situated near the water tap in the yard, and where a water cut-off valve to the home is located (underground). A long pole with a special end is inserted into the curb stop to turn off/on the water. Cut-in brace- Nominal 2-inch-thick members, usually 2 by 4's, cut in between each stud diagonally.

Dado- A groove cut into a board or panel intended to receive the edge of a connecting board or panel. Damper- A metal "door" placed within the fireplace chimney. Normally closed when the fireplace is not in use. Dampproofing- The black, tar like waterproofing material applied to the exterior of a foundation wall. Daylight- The end of a pipe (the terminal end) that is not attached to anything. Dead bolt- An exterior security lock installed on exterior entry doors that can be activated only with a key or thumb-turn. Unlike a latch, which has a beveled tongue, dead bolts have square ends. Dead light- The fixed, non-operable window section of a window unit. Deck, decked- To install the plywood or wafer board sheeting on the floor joists, rafters, or trusses. Dedicated circuit- An electrical circuit that serves only one appliance (ie, dishwasher) or a series of electric heaters or smoke detectors. Default- Breach of a mortgage contract (not making the required payments). De-humidistat- A control mechanism used to operate a mechanical ventilation system based upon the relative humidity in the home. Delamination- Separation of the plies in a panel due to failure of the adhesive. Usually caused by excessive moisture. Disconnect- A large (generally 20 Amp) electrical ON-OFF switch. Discount rate- A mortgage interest rate that is lower than the current rate for a certain period of time, e.g. 2.00% below variable rate for 2 years. Doorjamb, interior- The surrounding case into which and out of which a door closes and opens. It consists of two upright pieces, called side jambs, and a horizontal head jamb. These 3 jambs have the "door stop" installed on them.

Door operator- An automatic garage door opener. Door stop- The wooden style that the door slab will rest upon when it's in a closed position. Dormer- An opening in a sloping roof, the framing of which projects out to form a vertical wall suitable for windows or other openings. Double glass- Window or door in which two panes of glass are used with a sealed air space between. Also known as Insulating Glass. Double hung window- A window with two vertically sliding sashes, both of which can move up and down. Down payment- The difference between the sales price and the mortgage amount. A downpayment is usually paid at closing. Downspout- A pipe, usually of metal, for carrying rainwater down from the roof's horizontal gutters. Drain tile- A perforated, corrugated plastic pipe laid at the bottom of the foundation wall and used to drain excess water away from the foundation. It prevents ground water from seeping through the foundation wall. Sometimes called perimeter drain. Draw- The amount of progress billings on a contract that is currently available to a contractor under a contract with a fixed payment schedule. Drip- (a) A member of a cornice or other horizontal exterior finish course that has a projection beyond the other parts for throwing off water.(b) A groove in the underside of a sill or drip cap to cause water to drop off on the outer edge instead of drawing back and running down the face of the building. Drip cap- A molding or metal flashing placed on the exterior topside of a door or window frame to cause water to drip beyond the outside of the frame. Dry in- To install the black roofing felt (tar paper) on the roof.

Drywall (or Gypsum Wallboard (GWB), Sheet rock or Plasterboard)Wall board or gypsum- A manufactured panel made out of gypsum plaster and encased in a thin cardboard. Usually 1/2" thick and 4' x 8' or 4' x 12' in size. The panels are nailed or screwed onto the framing and the joints are taped and covered with a 'joint compound'. 'Green board' type drywall has a greater resistance to moisture than regular (white) plasterboard and is used in bathrooms and other "wet areas". Ducts- The heating system. Usually round or rectangular metal pipes installed for distributing warm (or cold) air from the furnace to rooms in the home. Also a tunnel made of galvanized metal or rigid fiberglass, which carries air from the heater or ventilation opening to the rooms in a building. Due-on-sale- A clause in a mortgage contract requiring the borrower to pay the entire outstanding balance upon sale or transfer of the property. Dura board, dura rock- A panel made out of concrete and fiberglass usually used as a ceramic tile backing material. Commonly used on bathtub decks. Sometimes called Wonder board DWV (drain-waste-vent)- The section of a plumbing system that carries water and sewer gases out of a home.

Earnest Money- A sum paid to the seller to show that a potential purchaser is serious about buying. Earthquake Strap- A metal strap used to secure gas hot water heaters to the framing or foundation of a house. Intended to reduce the chances of having the water heater fall over in an earthquake and causing a gas leak. Easement- A formal contract which allows a party to use another party's property for a specific purpose. e.g. A sewer easement might allow one party to run a sewer line through a neighbors property. Eaves- The horizontal exterior roof overhang. Egress- A means of exiting the home. An egress window is required in every bedroom and basement. Normally a 4' X 4' window is the minimum size required Elbow (ell)- A plumbing or electrical fitting that lets you change directions in runs of pipe or conduit. Electric lateral- The trench or area in the yard where the electric service line (from a transformer or pedestal) is located, or the work of installing the electric service to a home. Electric resistance coils- Metal wires that heat up when electric current passes through them and are used in baseboard heaters and electric water heaters. Electrical entrance package- The entry point of the electrical power including: (1) the 'strike' or location where the overhead or underground electrical lines connect to the house, (2) The meter which measures how much power is used and (3) The 'panel' or 'circuit breaker box ' (or 'fuse box') where the power can be shut off and where overload devices such a fuses or circuit breakers and located. Electrical Rough- Work performed by the Electrical Contractor after the plumber and heating contractor are complete with their phase of work. Normally all electrical wires, and outlet, switch, and fixture boxes are installed (before insulation).

Electrical Trim- Work performed by the electrical contractor when the house is nearing completion. The electrician installs all plugs, switches, light fixtures, smoke detectors, appliance "pig tails", bath ventilation fans, wires the furnace, and "makes up" the electric house panel. The electrician does all work necessary to get the home ready for and to pass the municipal electrical final inspection Elevation sheet- The page on the blue prints that depicts the house or room as if a vertical plane were passed through the structure. Equity- The "valuation" that you own in your home, i.e. the property value less the mortgage loan outstanding. Escrow - The handling of funds or documents by a third party on behalf of the buyer and/or seller. Estimate- The amount of labor, materials, and other costs that a contractor anticipates for a project as summarized in the contractor's bid proposal for the project. Escutcheon- An ornamental plate that fits around a pipe extending through a wall or floor to hide the cut out hole Estimating- The process of calculating the cost of a project. This can be a formal and exact process or a quick and imprecise process. Evaporator coil- The part of a cooling system that absorbs heat from air in your home. Also see condensing unit. Expansion joint- Fibrous material (@1/2" thick) installed in and around a concrete slab to permit it to move up and down (seasonally) along the nonmoving foundation wall. Expansive soils- Earth that swells and contracts depending on the amount of water that is present. ("Betonite" is an expansive soil). Exposed aggregate finish- A method of finishing concrete which washes the cement/sand mixture off the top layer of the aggregate - usually gravel. Often used in driveways, patios and other exterior surfaces.

Extras- Additional work requested of a contractor, not included in the original plan, which will be billed separately and will not alter the original contract amount, but increase the cost of building the home.

FHA strap- Metal straps that are used to repair a bearing wall "cut-out", and to "tie together" wall corners, splices, and bearing headers. Also, they are used to hang stairs and landings to bearing headers. Face nail- To install nails into the vertical face of a bearing header or beam. Faced concrete- To finish the front and all vertical sides of a concrete porch, step(s), or patio. Normally the "face" is broom finished. Facing brick- The brick used and exposed on the outside of a wall. Usually these have a finished texture. Fascia- Horizontal boards attached to rafter/truss ends at the eaves and along gables. Roof drain gutters are attached to the fascia. Felt- Tar paper. Installed under the roof shingles. Normally 15 lb. or 30 lb. Female- Any part, such as a nut or fitting, into which another (male) part can be inserted. Internal threads are female. Ferrule- Metal tubes used to keep roof gutters "open". Long nails (ferrule spikes) are driven through these tubes and hold the gutters in place along the fascia of the home. Field measure- To take measurements (cabinets, countertops, stairs, shower doors, etc.) in the home itself instead of using the blueprints. Finger joint- A manufacturing process of interlocking two shorter pieces of wood end to end to create a longer piece of dimensional lumber or molding. Often used in jambs and casings and are normally painted (instead of stained). Fire block- Short horizontal members sometimes nailed between studs, usually about halfway up a wall. See also 'Fire stop'. Fire brick- Brick made of refractory ceramic material which will resist high temperatures. Used in a fireplace and boiler. Fireplace chase flashing pan- A large sheet of metal that is installed around and perpendicular to the fireplace flue pipe. It's purpose is to confine and limit the spread of fire and smoke to a small area.

Fire-resistive or Fire rated- Applies to materials that are not combustible in the temperatures of ordinary fires and will withstand such fires for at least 1 hour. Drywall used in the garage and party walls are to be fire rated, 5/8", Type X. Fire retardant chemical- A chemical or preparation of chemicals used to reduce the flammability of a material or to retard the spread of flame. Fire stop- A solid, tight closure of a concealed space, placed to prevent the spread of fire and smoke through such a space. In a frame wall, this will usually consist of 2 by 4 cross blocking between studs. Work performed to slow the spread of fire and smoke in the walls and ceiling (behind the drywall). Includes stuffing wire holes in the top and bottom plates with insulation, and installing blocks of wood between the wall studs at the drop soffit line. This is integral to passing a Rough Frame inspection. See also 'Fire block'. Fishplate (gusset)- A wood or plywood piece used to fasten the ends of two members together at a butt joint with nails or bolts. Sometimes used at the junction of opposite rafters near the ridge line. Sometimes called a gang nail plate. Fish tape- A long strip of spring steel used for fishing cables and for pulling wires through conduit. Fixed price contract- A contract with a set price for the work. See Time and Materials Contract. Fixed rate- A loan where the initial payments are based on a certain interest rate for a stated period . The rate payable will not change during this period regardless of changes in the lender's standard variable rate. Fixed Rate Mortgage- A mortgage with an interest rate that remains the same over the years. Flagstone (flagging or flags)- Flat stones (1 to 4 inches thick) used for walks, steps, floors, and vertical veneer (in lieu of brick). Flakeboard- A manufactured wood panel made out of 1"- 2" wood chips and glue. Often used as a substitute for plywood in the exterior wall and roof sheathing. Also called OSB or wafer board.

Flame retention burner- An oil burner, designed to hold the flame near the nozzle surface. Generally the most efficient type for residential use. Flashing- Sheet metal or other material used in roof and wall construction to protect a building from water seepage. Flat mold- Thin wood strips installed over the butt seam of cabinet skins. Flat paint- An interior paint that contains a high proportion of pigment and dries to a flat or lusterless finish. Flatwork- Common word for concrete floors, driveways, basements, and sidewalks. Floating- The next-to-last stage in concrete work, when you smooth off the job and bring water to the surface by using a hand float or bull float. Floating wall- A non-bearing wall built on a concrete floor. It is constructed so that the bottom two horizontal plates can compress or pull apart if the concrete floor moves up or down. Normally built on basements and garage slabs. Fluorescent lighting- A fluorescent lamp is a gas-filled glass tube with a phosphur coating on the inside. Gas inside the tube is ionized by electricity which causes the phosphur coating to glow. Normally with two pins that extend from each end. Flue- Large pipe through which fumes escape from a gas water heater, furnace, or fireplace. Normally these flue pipes are double walled, galvanized sheet metal pipe and sometimes referred to as a "B Vent". Fireplace flue pipes are normally triple walled. In addition, nothing combustible shall be within one inch from the flue pipe. Flue collar- Round metal ring which fits around the heat flue pipe after the pipe passes out of the roof. Flue damper- An automatic door located in the flue that closes it off when the burner turns off; purpose is to reduce heat loss up the flue from the stillwarm furnace or boiler.

Flue lining- 2-foot lengths, fire clay or terra-cotta pipe (round or square) and usually madein all ordinary flue sizes. Used for the inner lining of chimneys with the brick or masonry work done around the outside. Flue linings in chimneys runs from one foot below the flue connection to the top of the chimney. Fly rafters- End rafters of the gable overhang supported by roof sheathing and lookouts. Footer, footing- Continuous 8" or 10" thick concrete pad installed before and supports the foundation wall or monopost. Forced air heating - A common form of heating with natural gas, propane, oil or electricity as a fuel. Air is heated in the furnace and distributed through a set of metal ducts to various areas of the house. Form- Temporary structure erected to contain concrete during placing and initial hardening. Foundation- The supporting portion of a structure below the first floor construction, or below grade, including the footings. Foundation ties- Metal wires that hold the foundation wall panels and rebar in place during the concrete pour. Foundation waterproofing- High-quality below-grade moisture protection. Used for below-grade exterior concrete and masonry wall damp-proofing to seal out moisture and prevent corrosion. Normally looks like black tar. Frame Inspection- The act of inspecting the home's structural integrity and it's complianceto local municipal codes. Framer-The carpenter contractor that installs the lumber and erects the frame, flooring system, interior walls, backing, trusses, rafters, decking, installs all beams, stairs, soffits and all work related to the wood structure of the home. The framer builds the home according to the blueprints and must comply with local building codes and regulations. Framing- Lumber used for the structural members of a building, such as studs, joists, and rafters.

Frieze- In house construction a horizontal member connecting the top of the siding with the soffit of the cornice. Frost lid- Round metal lid that is installed on a water meter pit. Frost line- The depth of frost penetration in soil and/or the depth at which the earth will freeze and swell. This depth varies in different parts of the country. Furring strips- Strips of wood, often 1 X 2 and used to shim out and provide a level fastening surface for a wall or ceiling. Fuse- A device often found in older homes designed to prevent overloads in electrical lines. This protects against fire. See also 'circuit breakers'.

GF C I, or G F I- Ground Fault Circuit Interrupter- an ultra sensitive plug designed to shut off all electric current. Used in bathrooms, kitchens, exterior waterproof outlets, garage outlets, and "wet areas". Has a small reset button on the plug. Gable- The end, upper, triangular area of a home, beneath the roof. Gang nail plate- A steel plate attached to both sides at each joint of a truss. Sometimes called a fishplate or gussett. Gate valve- A valve that lets you completely stop—but not modulate—the flow within a pipe. General Contractor A contractor who enters into a contract with the owner of a project for the construction of the project and who takes full responsibility for its completion, although the contractor may enter into subcontracts with others for the performance of specific parts or phases of the project. Gas lateral- The trench or area in the yard where the gas line service is located, or the work of installing the gas service to a home. Girder- A large or principal beam of wood or steel used to support concentrated loads at isolated points along its length. Glazing- The process of installing glass, which commonly is secured with glazier's points and glazing compound. Globe valve- A valve that lets you adjust the flow of water to any rate between fully on and fully off. Also see gate valve. Gloss enamel- A finishing paint material. Forms a hard coating with maximum smoothness of surface and dries to a sheen or luster (gloss) Glued Laminated Beam (Glulam)- A structural beam composed of wood laminations or lams. The lams are pressure bonded with adhesives to attain a typical thickness of 1 ½" . (It looks like 5 or more 2 X 4's are glued together). Grade- Ground level, or the elevation at any given point. Also the work of leveling dirt. Also the designated quality of a manufactured piece of wood.

Grade beam- A foundation wall that is poured @ level with or just below the grade of theearth. An example is the area where the 8' or 16' overhead garage door "block out" is located, or a lower (walk out basement) foundation wall is poured Graduated Payment Mortgage (GPM) - A fixed-rate, fixed-schedule loan. It starts with lower payments than a level payment loan; payments rise annually, with the entire increase being used to reduce the outstanding balance. The increase in payments may enable the borrower to pay off a 30year loan in 15 to 20 years, or less. Grain- The direction, size, arrangement, appearance, or quality of the fibers in wood. Grid- The completed assembly of main and cross tees in a suspended ceiling system before the ceiling panels are installed. Also the decorative slats (munton) installed between glass panels. Ground- Refers to electricity's habit of seeking the shortest route to earth. Neutral wires carry it there in all circuits. An additional grounding wire or the sheathing of the metal-clad cable or conduit—protects against shock if the neutral leg is interrupted. Ground fault- Ground Fault Circuit Interrupter (GFCI, GFI)- an ultra sensitive plug designed to shut off all electric current. Used in bathrooms, kitchens, exterior waterproof outlets, garage outlets, and "wet areas". Has a small reset button on the plug. Ground iron- The plumbing drain and waste lines that are installed beneath the basement floor. Cast iron was once used, but black plastic pipe (ABS) is now widely used. Groundwater- Water from an aquifer or subsurface water source. Grout- A wet mixture of cement, sand and water that flows into masonry or ceramic crevices to seal the cracks between the different pieces. Mortar made of such consistency (by adding water) that it will flow into the joints and cavities of the masonry work and fill them solid. Gusset- A flat wood, plywood, or similar type member used to provide a connection at the intersection of wood members. Most commonly used at

joints of wood trusses. They are fastened by nails, screws, bolts, or adhesives. Gutter- A shallow channel or conduit of metal or wood set below and along the (fascia) eaves of a house to catch and carry off rainwater from the roof. Gyp board- Drywall. Wall board or gypsum- A panel (normally 4' X 8', 10', 12', or 16')made with a core of Gypsum (chalk-like) rock, which covers interior walls and ceilings. Gypsum plaster- Gypsum formulated to be used with the addition of sand and water for base-coat plaster.

H Clip- Small metal clips formed like an "H" that fits at the joints of two plywood (or wafer board) sheets to stiffen the joint. Normally used on the roof sheeting. Hardware- All of the "metal" fittings that go into the home when it is near completion. For example, door knobs, towel bars, handrail brackets, closet rods, house numbers, door closers, etc. The Interior Trim Carpenter installs the "hardware". Haunch- An extension, knee like protrusion of the foundation wall that a concrete porch or patio will rest upon for support. Hazard insurance - Protection against damage caused by fire, windstorms, or other common hazards. Many lenders require borrowers to carry it in an amount at least equal to the mortgage. Header- (a) A beam placed perpendicular to joists and to which joists are nailed inframing for a chimney, stairway, or other opening. (b) A wood lintel. (c) The horizontal structural member over an opening (for example over a door or window). Hearth- The fireproof area directly in front of a fireplace. The inner or outer floor of a fireplace, usually made of brick, tile, or stone. Heating load- The amount of heating required to keep a building at a specified temperature during the winter, usually 65° F, regardless of outside temperature. Heat meter- An electrical municipal inspection of the electric meter breaker panel box. Heat pump- A mechanical device which uses compression and decompression of gas to heat and/or cool a house. Heat Rough- Work performed by the Heating Contractor after the stairs and interior walls are built. This includes installing all duct work and flue pipes. Sometimes, the furnace and fireplaces are installed at this stage of construction. Heat Trim- Work done by the Heating Contractor to get the home ready for the municipal Final Heat Inspection. This includes venting the hot water

heater, installing all vent grills, registers, air conditioning services, turning on the furnace, installing thermostats, venting ranges and hoods, and all other heat related work. Heel cut- A notch cut in the end of a rafter to permit it to fit flat on a wall and on the top, doubled, exterior wall plate. Highlights- A light spot, area, or streak on a painted surface. Hip- A roof with four sloping sides. The external angle formed by the meeting of two sloping sides of a roof. Hip roof- A roof that rises by inclined planes from all four sides of a building. Home run (electrical)- The electrical cable that carries power from the main circuit breaker panel to the first electrical box, plug, or switch in the circuit. Honey combs- The appearance concrete makes when rocks in the concrete are visible and where there are void areas in the foundation wall, especially around concrete foundation windows. Hose bib- An exterior water faucet (sill cock). Hot wire- The wire that carries electrical energy to a receptacle or other device—in contrast to a neutral, which carries electricity away again. Normally the black wire. Also see ground. Humidifier- An appliance normally attached to the furnace, or portable unit device designed to increase the humidity within a room or a house by means of the discharge of water vapor. Hurricane clip- Metal straps that are nailed and secure the roof rafters and trusses to the top horizontal wall plate. Sometimes called a Teco clip. H V A C- An abbreviation for Heat, Ventilation, and Air Conditioning

I-beam- A steel beam with a cross section resembling the letter I. It is used for long spans as basement beams or over wide wall openings, such as a double garage door, when wall and roof loads bear down on the opening. I-joist- Manufactured structural building component resembling the letter "I". Used as floor joists and rafters. I-joists include two key parts: flanges and webs. The flange of the I joist may be made of laminated veneer lumber or dimensional lumber, usually formed into a 1 ½" width. The web or center of the I-joist is commonly made of plywood or oriented strand board (OSB). Large holes can be cut in the web to accommodate duct work and plumbing waste lines. I-joists are available in lengths up to 60 feet long Incandescent lamp- A lamp employing an electrically charged metal filament that glows at white heat. A typical light bulb. Index- The interest rate or adjustment standard that determines the changes in monthly payments for an adjustable rate loan. Infiltration- The passage of air from indoors to outdoors and vice versa; term is usually associated with drafts from cracks, seams or holes in buildings. Inside corner- The point at which two walls form an internal angle, as in the corner of a room. Insulating glass- Window or door in which two panes of glass are used with a sealed air space between. Also known as Double glass. Insulation board, rigid- A structural building board made of coarse wood or cane fiber in ½- and 25/32-inch thickness. It can be obtained in various size sheets and densities. Insulation- Any material high in resistance to heat transmission that, when placed in the walls, ceiling, or floors of a structure, and will reduce the rate of heat flow. Interest - The cost paid to a lender for borrowed money. Interior finish- Material used to cover the interior framed areas of walls and ceilings

Irrigation- Lawn sprinkler system.

J Channel- Metal edging used on drywall to give the edge a better finished appearance when a wall is not "wrapped" Generally, basement stairway walls have drywall only on the stair side. J Channel is used on the vertical edge of the last drywall sheet Jack post- A type of structural support made of metal, which can be raised or lowered through a series of pins and a screw to meet the height required. Basically used as a replacement for an old supporting member in a building. See Monopost. Jack rafter- A rafter that spans the distance from the wall plate to a hip, or from a valley to a ridge. Jamb- The side and head lining of a doorway, window, or other opening. Includes studs as well as the frame and trim. Joint- The location between the touching surfaces of two members or components joined and held together by nails, glue, cement, mortar, or other means. Joint cement or Joint compound- A powder that is usually mixed with water and used for joint treatment in gypsum-wallboard finish. Often called "spackle" or drywall mud. Joint tenancy- A form of ownership in which the tenants own a property equally. If one dies, the other automatically inherits the entire property. Joint trench- When the electric company and telephone company dig one trench and "drop" both of their service lines in. Joist- Wooden 2 X 8's, 10's, or 12's that run parallel to one another and support a floor or ceiling, and supported in turn by larger beams, girders, or bearing walls. Joist hanger- A metal "U" shaped item used to support the end of a floor joist and attached with hardened nails to another bearing joist or beam. Jumpers- Water pipe installed in a water meter pit (before the water meter is installed), or electric wire that is installed in the electric house panel meter socket before the meter is installed. This is sometimes illegal.

Keeper- The metal latch plate in a door frame into which a doorknob plunger latches. Keyless- A plastic or porcelain light fixture that operates by a pull string. Generally found in the basement, crawl space , and attic areas. Keyway- A slot formed and poured on a footer or in a foundation wall when another wall will be installed at the slot location. This gives additional strength to the joint/meeting point. Kilowatt (kw)- One thousand watts. A kilowatt hour is the base unit used in measuring electrical consumption. Also see watt. King stud- The vertical "2 X's" frame lumber (left and right) of a window or door opening, and runs continuously from the bottom sole plate to the top plate. Knot- In lumber, the portion of a branch or limb of a tree that appears on the edge or face of the piece.

Laminated shingles - Shingles that have added dimensionality because of extra layers or tabs, giving a shake-like appearance. May also be called "architectural shingles" or "three-dimensional shingles." Laminating- Bonding together two or more layers of materials. Landing- A platform between flights of stairs or at the termination of a flight of stairs. Often used when stairs change direction. Normally no less than 3 ft. X 3 ft. square. Lap- To cover the surface of one shingle or roll with another. Latch- A beveled metal tongue operated by a spring-loaded knob or lever. The tongue's bevel lets you close the door and engage the locking mechanism, if any, without using a key. Contrasts with dead bolt. Lateral (electric, gas, telephone, sewer and water)- The underground trench and related services (i.e., electric, gas, telephone, sewer and water lines) that will be buried within the trench. Lath- A building material of narrow wood, metal, gypsum, or insulating board that is fastened to the frame of a building to act as a base for plaster, shingles, or tiles. Lattice- An open framework of criss-crossed wood or metal strips that form regular, patterned spaces. Ledger (for a Structural Floor)- The wooden perimeter frame lumber member that bolts onto the face of a foundation wall and supports the wood structural floor. Ledger strip- A strip of lumber nailed along the bottom of the side of a girder on which joists rest. Leech field- A method used to treat/dispose of sewage in rural areas not accessible to a municipal sewer system. Sewage is permitted to be filtered and eventually discharged into a section of the lot called a leech field. Let-in brace- Nominal 1 inch-thick boards applied into notched studs diagonally. Also, an "L" shaped, long (@ 10') metal strap that are installed

by the framer at the rough stage to give support to an exterior wall or wall corner. Level- True horizontal. Also a tool used to determine level. Level Payment Mortgage- A mortgage with identical monthly payments over the life of the loan. Lien- An encumbrance that usually makes real or personal property the security for payment of a debt or discharge of an obligation. Light- Space in a window sash for a single pane of glass. Also, a pane of glass. Limit switch- A safety control that automatically shuts off a furnace if it gets too hot. Most also control blower cycles. Lineal foot- A unit of measure for lumber equal to 1 inch thick by 12 inches wide by 12 inches long. Examples: 1" x 12" x 16' = 16 board feet, 2" x 12" x 16' = 32 board feet. Lintel- A horizontal structural member that supports the load over an opening such as a door or window. Load bearing wall- Includes all exterior walls and any interior wall that is aligned above a support beam or girder. Normally, any wall that has a double horizontal top plate. Loan- The amount to be borrowed. Loan to value ratio- The ratio of the loan amount to the property valuation and expressed as a percentage. E.g. if a borrower is seeking a loan of $200,000 on a property worth $400,000 it has a 50% loan to value rate. If the loan were $300,000, the LTV would be 75%. The higher the loan to value, the greater the lender's perceived risk. Loans above normal lending LTV ratios may require additional security. Lookout- A short wood bracket or cantilever that supports an overhang portion of a roof.

Louver- A vented opening into the home that has a series of horizontal slats and arranged to permit ventilation but to exclude rain, snow, light, insects, or other living creatures. Lumens- Unit of measure for total light output. The amount of light falling on a surface of one square foot.

Male- Any part, such as a bolt, designed to fit into another (female) part. External threads are male. Mantel- The shelf above a fireplace opening. Also used in referring to the decorative trim around a fireplace opening. Manufactured wood- A wood product such as a truss, beam, gluelam, microlam or joist which is manufactured out of smaller wood pieces and glued or mechanically fastened to form a larger piece. Often used to create a stronger member which may use less wood. See also Oriented Strand Board. Manufacturer's specifications- The written installation and/or maintenance instructions which are developed by the manufacturer of a product and which may have to be followed in order to maintain the product warrantee. Masonry- Stone, brick, concrete, hollow-tile, concrete block, or other similar building units or materials. Normally bonded together with mortar to form a wall. Mastic- A pasty material used as a cement (as for setting tile) or a protective coating (as for thermal insulation or waterproofing) Mechanics lien- A lien on real property, created by statue in many years, in favor of persons supplying labor or materials for a building or structure, for the value of labor or materials supplied by them. In some jurisdictions, a mechanics lien also exists for the value of professional services. Clear title to the property cannot be obtained until the claim for the labor, materials, or professional services is settled. Timely filing is essential to support the encumbrance, and prescribed filing dates vary by jurisdiction. Metal lath- Sheets of metal that are slit to form openings within the lath. Used as a plaster base for walls and ceilings and as reinforcing over other forms of plaster base. Microlam- A manufactured structural wood beam. It is constructed of pressure and adhesive bonded wood strands of wood. They have a higher strength rating than solid sawn lumber. Normally comes in l ½" thickness' and 9 ½", 11 ½" and 14" widths Milar (mylar)- Plastic, transparent copies of a blueprint.

Millwork- Generally all building materials made of finished wood and manufactured in millwork plants. Includes all doors, window and door frames, blinds, mantels, panelwork, stairway components (ballusters, rail, etc.), moldings, and interior trim. Does not include flooring, ceiling, or siding. Miter joint- The joint of two pieces at an angle that bisects the joining angle. For example, the miter joint at the side and head casing at a door opening is made at a 45° angle. Molding- A wood strip having an engraved, decorative surface. Monopost- Adjustable metal column used to support a beam or bearing point. Normally 11 gauge or Schedule 40 metal, and determined by the structural engineer Mortar- A mixture of cement (or lime) with sand and water used in masonry work. Mortgage- Loan secured by land. Mortgage broker - A broker who represents numerous lenders and helps consumers find affordable mortgages; the broker charges a fee only if the consumer finds a loan. Mortgage company - A company that borrows money from a bank, lends it to consumers to buy homes, then sells the loans to investors. Mortgage deed- Legal document establishing a loan on property. Mortgagee- The lender who makes the mortgage loan. Mortgage loan- A contract in which the borrower's property is pledged as collateral. It is repaid in installments. The mortgagor (buyer) promises to repay principal and interest, keep the home insured, pay all taxes and keep the property in good condition. Mortgage Origination Fee- A charge for work involved in preparing and servicing a mortgage application (usually one percent of the loan amount).

Mortise- A slot cut into a board, plank, or timber, usually edgewise, to receive the tenon (or tongue) of another board, plank, or timber to form a joint. Mudsill- Bottom horizontal member of an exterior wall frame which rests on top a foundation, sometimes called sill plate. Also sole plate, bottom member of interior wall frame. Mullion- A vertical divider in the frame between windows, doors, or other openings. Muntin- A small member which divides the glass or openings of sash or doors. Muriatic acid- Commonly used as a brick cleaner after masonry work is completed. Mushroom- The unacceptable occurrence when the top of a caisson concrete pier spreads out and hardens to become wider than the foundation wall thickness.

Nail inspection- An inspection made by a municipal building inspector after the drywall material is hung with nails and screws (and before taping). Natural finish- A transparent finish which does not seriously alter the original color or grain of the natural wood. Natural finishes are usually provided by sealers, oils, varnishes, water repellent preservatives, and other similar materials. NEC (National Electrical Code)- A set of rules governing safe wiring methods. Local codes—which are backed by law—may differ from the NEC in some ways. Neutral wire- Usually color-coded white, this carries electricity from an outlet back to the service panel. Also see hot wire and ground. Newel post- The large starting post to which the end of a stair guard railing or balustrade is fastened. Nonbearing wall- A wall supporting no load other than its own weight. Nosing- The projecting edge of a molding or drip or the front edge of a stair tread. Notch- A crosswise groove at the end of a board. Note- A formal document showing the existence of a debt and stating the terms of repayment. Nozzle- The part of a heating system that sprays the fuel of fuel-air mixture into the combustion chamber.

O C- On Center- The measurement of spacing for studs, rafters, and joists in a building from the center of one member to the center of the next. Oakum- Loose hemp or jute fiber that's impregnated with tar or pitch and used to caulk large seams or for packing plumbing pipe joints Open hole inspection- When an engineer (or municipal inspector) inspects the open excavation and examines the earth to determine the type of foundation (caisson, footer, wall on ground, etc.) that should be installed in the hole. Oriented Strand Board or OSB- A manufactured 4' X 8' wood panel made out of 1"- 2" wood chips and glue. Often used as a substitute for plywood. Outrigger- An extension of a rafter beyond the wall line. Usually a smaller member nailed to a larger rafter to form a cornice or roof overhang. Outside corner- The point at which two walls form an external angle, one you usually can walk around. Overhang- Outward projecting eave-soffit area of a roof; the part of the roof that hangs out or over the outside wall. See also Cornice.

Padding- A material installed under carpet to add foot comfort, isolate sound, and to prolong carpet life. Pad out, pack out- To shim out or add strips of wood to a wall or ceiling in order that the finished ceiling/wall will appear correct. Paint- A combination of pigments with suitable thinners or oils to provide decorative and protective coatings. Can be oil based or latex water based. Pallets- Wooden platforms used for storing and shipping material. Forklifts and hand trucks are used to move these wooden platforms around. Panel- A thin flat piece of wood, plywood, or similar material, framed by stiles and rails as in a door (or cabinet door), or fitted into grooves of thicker material with molded edges for decorative wall treatment. Paper, building- A general term for papers, felts, and similar sheet materials used in buildings without reference to their properties or uses. Generally comes in long rolls. Parapet- A wall placed at the edge of a roof to prevent people from falling off. Parting stop or strip- A small wood piece used in the side and head jambs of double hung windows to separate the upper sash from the lower sash. Particle board- Plywood substitute made of course sawdust that is mixed with resin and pressed into sheets. Used for closet shelving, floor underlayment, stair treads, etc. Partition- A wall that subdivides spaces within any story of a building or room. Paver, paving- Materials—commonly masonry—laid down to make a firm, even surface. Payment schedule- A pre-agreed upon schedule of payments to a contractor usually based upon the amount of work completed. Such a schedule may include a deposit prior to the start of work. There may also be a temporary 'retainer' (5-10% of the total cost of the job) at the end of the contract for correcting any small items which have not been completed or repaired.

Pedestal- A metal box installed at various locations along utility easements that contain electrical, telephone, or cable television switches and connections. Penalty clause - A provision in a contract that provides for a reduction in the amount otherwise payable under a contract to a contractor as a penalty for failure to meet deadlines or for failure of the project to meet contract specifications. Penny- As applied to nails, it originally indicated the price per hundred. The term now series as a measure of nail length and is abbreviated by the letter "d". Normally, 16d (16 "penny") nails are used for framing Percolation test or perc. test- Tests that a soil engineer performs on earth to determine the feasibility of installing a leech field type sewer system on a lot. A test to determine if the soil on a proposed building lot is capable of absorbing the liquid affluent from a septic system. Performance bond- An amount of money (usually 10% of the total price of a job) that a contractor must put on deposit with a governmental agency as an insurance policy that guarantees the contractors' proper and timely completion of a project or job. Perimeter drain- 3" or 4" perforated plastic pipe that goes around the perimeter (either inside or outside) of a foundation wall (before backfill) and collects and diverts ground water away from the foundation. Generally, it is "daylighted" into a sump pit inside the home, and a sump pump is sometimes inserted into the pit to discharge any accumulation of water. Permeability- A measure of the ease with which water penetrates a material. Permit - A governmental municipal authorization to perform a building process as in: · Zoning\Use permit - Authorization to use a property for a specific use e.g. a garage, a single family residence etc. · Demolition permit - Authorization to tear down and remove an existing structure.

· Grading permit - Authorization to change the contour of the land. · Septic permit - A health department authorization to build or modify a septic system. · Building permit - Authorization to build or modify a structure. · Electrical permit - A separate permit required for most electrical work. · Plumbing permit - A separate permit required for new plumbing and larger modifications of existing plumbing systems. Pigtails, electrical- The electric cord that the electrician provides and installs on an appliance such as a garbage disposal, dishwasher, or range hood. Pier- A column of masonry, usually rectangular in horizontal cross section, used to support other structural members. Also see Caisson. Pigment- A powdered solid used in paint or enamel to give it a color. Pilot hole- A small-diameter, pre-drilled hole that guides a nail or screw. Pilot light- A small, continuous flame (in a hot water heater, boiler, or furnace) that ignites gas or oil burners when needed. Pitch- The incline slope of a roof or the ratio of the total rise to the total width of a house, i.e., a 6-foot rise and 24-foot width is a one-fourth pitch roof. Roof slope is expressed in the inches of rise, per foot of horizontal run. PITI - Principal, interest, taxes and insurance (the four major components of monthly housing payments). Plan view- Drawing of a structure with the view from overhead, looking down. Plate- Normally a 2 X 4 or 2 X 6 that lays horizontally within a framed structure, such as: 

Sill plate- A horizontal member anchored to a concrete or masonry wall.



Sole plate- Bottom horizontal member of a frame wall.



Top plate- Top horizontal member of a frame wall supporting ceiling joists, rafters, or other members.

Plenum- The main hot-air supply duct leading from a furnace. Plot plan- An overhead view plan that shows the location of the home on the lot. Includes all easements, property lines, set backs, and legal descriptions of the home. Provided by the surveyor. Plough, plow- To cut a lengthwise groove in a board or plank. An exterior handrail normally has a ploughed groove for hand gripping purposes Plumb- Exactly vertical and perpendicular. Plumb bob- A lead weight attached to a string. It is the tool used in determining plumb. Plumbing boots- Metal saddles used to strengthen a bearing wall/vertical stud(s) where a plumbing drain line has been cut through and installed. Plumbing ground- The plumbing drain and waste lines that are installed beneath a basement floor. Plumbing jacks- Sleeves that fit around drain and waste vent pipes at, and are nailed to, the roof sheeting. Plumbing rough- Work performed by the plumbing contractor after the Rough Heat is installed. This work includes installing all plastic ABS drain and waste lines, copper water lines, bath tubs, shower pans, and gas piping to furnaces and fireplaces. Lead solder should not be used on copper piping. Plumbing stack- A plumbing vent pipe that penetrates the roof. Plumbing trim- Work performed by the plumbing contractor to get the home ready for a final plumbing inspection. Includes installing all toilets (water closets), hot water heaters, sinks, connecting all gas pipe to appliances, disposal, dishwasher, and all plumbing items. Plumbing waste line- Plastic pipe used to collect and drain sewage waste.

Ply- A term to denote the number of layers of roofing felt, veneer in plywood, or layers in built-up materials, in any finished piece of such material. Plywood- A panel (normally 4' X 8') of wood made of three or more layers of veneer, compressed and joined with glue, and usually laid with the grain of adjoining plies at right angles to give the sheet strength. Point load- A point where a bearing/structural weight is concentrated and transferred to the foundation. Portland cement- Cement made by heating clay and crushed limestone into a brick and then grinding to a pulverized powder state. Post- A vertical framing member usually designed to carry a beam. Often a 4" x 4", a 6" x 6", or a metal pipe with a flat plate on top and bottom. Post-and-beam- A basic building method that uses just a few hefty posts and beams to support an entire structure. Contrasts with stud framing. Power vent- A vent that includes a fan to speed up air flow. Often installed on roofs. Premium- Amount payable on a loan. Preservative-. Any pesticide substance that, for a reasonable length of time, will prevent the action of wood-destroying fungi, insect borers, and similar destructive agents when the wood has been properly coated or impregnated with it. Normally an arsenic derivative. Chromated Copper Arsenate (CCA) is an example. Pressure Relief Valve (PRV)- A device mounted on a hot water heater or boiler which is designed to release any high steam pressure in the tank to prevent tank explosions. Pressure-treated wood- Lumber that has been saturated with a preservative. Primer- The first, base coat of paint when a paint job consists of two or more coats. A first coating formulated to seal raw surfaces and holding succeeding finish coats.

Principal- The original amount of the loan, the capital. Property survey- A survey to determine the boundaries of your property. The cost depends on the complexity of the survey. P trap- Curved, "U" section of drain pipe that holds a water seal to prevent sewer gasses from entering the home through a fixtures water drain. Pump mix- Special concrete that will be used in a concrete pump. Generally, the mix has smaller rock aggregate than regular mix. Punch list- A list of discrepancies that need to be corrected by the contractor. Punch out- To inspect and make a discrepancy list. Putty- A type of dough used in sealing glass in the sash, filling small holes and crevices in wood, and for similar purposes. PVC or CPVC - Poly Vinyl Chloride-A type of white or light gray plastic pipe sometimes used for water supply lines and waste pipe.

Quarry tile- A man-made or machine-made clay tile used to finish a floor or wall. Generally 6" X 6" X 1/4" thick . Quarter round- A small trim molding that has the cross section of a quarter circle.

Rabbet- A rectangular longitudinal groove cut in the corner edge of a board or plank. Radiant heating- A method of heating, usually consisting of a forced hot water system with pipes placed in the floor, wall, or ceiling. Also electrically heated panels. Radiation- Energy transmitted from a heat source to the air around it. Radiators actually depend more on convection than radiation. Radon- A naturally-occurring, heavier than air, radioactive gas common in many parts of the country. Radon gas exposure is associated with lung cancer. Mitigation measures may involve crawl space and basement venting and various forms of vapor barriers. Radon system- A ventilation system beneath the floor of a basement and/or structural wood floor and designed to fan exhaust radon gas to the outside of the home Rafter- Lumber used to support the roof sheeting and roof loads. Generally, 2 X 10's and 2 X 12's are used. The rafters of a flat roof are sometimes called roof joists. Rafter, hip- A rafter that forms the intersection of an external roof angle. Rafter, valley- A rafter that forms the intersection of an internal roof angle. The valley rafter is normally made of double 2-inch-thick members. Rail- Cross members of panel doors or of a sash. Also, a wall or open balustrade placed at the edge of a staircase, walkway bridge, or elevated surface to prevent people from falling off. Any relatively lightweight horizontal element, especially those found in fences (split rail). Railroad tie- Black, tar and preservative impregnated, 6" X 8" and 6'-8' long wooden timber that was used to hold railroad track in place. Normally used as a member of a retaining wall. Rake- Slope or slanted. Rake fascia- The vertical face of the sloping end of a roof eave.

Rake siding- The practice of installing lap siding diagonally Ranch- A single story, one level home. Ready mixed concrete- Concrete mixed at a plant or in trucks en route to a job and delivered ready for placement. Rebar, reinforcing bar-Ribbed steel bars installed in foundation concrete walls, footers, and poured in place concrete structures designed to strengthen concrete. Comes in various thickness' and strength grade. Receptacle- An electrical outlet. A typical household will have many 120 volt receptacles for plugging in lams and appliances and 240 volt receptacles for the range, clothes dryer, air conditioners, etc. Recording fee - A charge for recording the transfer of a property, paid to a city, county, or other appropriate branch of government. Redline, red lined prints- Blueprints that reflect changes and that are marked with red pencil. Reducer- A fitting with different size openings at either end and used to go from a larger to a smaller pipe. Reflective insulation- Sheet material with one or both faces covered with aluminum foil. Refrigerant- A substance that remains a gas at low temperatures and pressure and can be used to transfer heat. Freon is an example and is used in air conditioning systems. Register- A grill placed over a heating duct or cold air return. Reglaze- To replace a broken window. Relief valve- A device designed to open if it detects excess temperature or pressure. Remote- Remote electrical, gas, or water meter digital readouts that are installed near the front of the home in order for utility companies to easily read the home owners usage of the service.

Retaining wall- A structure that holds back a slope and prevents erosion. Retentions- Amounts withheld from progress billings until final and satisfactory project completion. R factor or value- A measure of a materials resistance to the passage of heat. New homewalls are usually insulated with 4" of batt insulation with an R value of R-13, and a ceiling insulation of R-30. Ribbon (girt)- Normally a 1 X 4 board let into the studs horizontally to support the ceiling or second-floor joists. Ridge- The horizontal line at the junction of the top edges of two sloping roof surfaces. Ridge board- The board placed on the ridge of the roof onto which the upper ends of other rafters are fastened. Ridge shingles- Shingles used to cover the ridge board. Rim joist- A joist that runs around the perimeter of the floor joists and home. Rise- The vertical distance from the eaves line to the ridge. Also the vertical distance from stair tread to stair tread (and not to exceed 7 ½"). Riser- Each of the vertical boards closing the spaces between the treads of stairways. Riser and panel- The exterior vertical pipe (riser) and metal electric box (panel) the electrician provides and installs at the "Rough Electric" stage. Road base- A aggregate mixture of sand and stone. Rock 1, 2, 3- When referring to drywall, this means to install drywall to the walls and ceilings (with nails and screws), and before taping is performed. Roll, rolling- To install the floor joists or trusses in their correct place. (To "roll the floor" means to install the floor joists). Romex- A name brand of nonmetallic sheathed electrical cable that is used for indoor wiring.

Roll roofing- Asphalt roofing products manufactured in roll form. 36-inch wide rolls with and 108 square feet of material. Weights are generally 45 to 90 pounds per roll. Romex- A name brand of nonmetallic sheathed electrical cable that is used for indoor wiring. Roof jack- Sleeves that fit around the black plumbing waste vent pipes at, and are nailed to, the roof sheeting. Roof joist- The rafters of a flat roof. Lumber used to support the roof sheeting and roof loads. Generally, 2 X 10's and 2 X 12's are used. Roof sheathing or sheeting- The wood panels or sheet material fastened to the roof rafters or trusses on which the shingle or other roof covering is laid. Roof valley- The "V" created where two sloping roofs meet. Rough opening- The horizontal and vertical measurement of a window or door opening before drywall or siding is installed. Rough sill- The framing member at the bottom of a rough opening for a window. It is attached to the cripple studs below the rough opening. Roughing-in- The initial stage of a plumbing, electrical, heating, carpentry, and/or other project, when all components that won't be seen after the second finishing phase are assembled. See also Heat Rough, Plumbing Rough, and Electrical Rough. Run, roof - The horizontal distance from the eaves to a point directly under the ridge. One half the span. Run, stair- the horizontal distance of a stair tread from the nose to the riser. R Value- A measure of insulation. A measure of a materials resistance to the passage of heat. The higher the R value, the more insulating "power" it has. For example, typical new home's walls are usually insulated with 4" of batt insulation with an R value of R-13, and a ceiling insulation of R30.

Saddle- A small second roof built behind the back side of a fireplace chimney to divert water around the chimney. Also, the plate at the bottom of some—usually exterior—door openings. Sometimes called a threshold. Sack mix- The amount of Portland cement in a cubic yard of concrete mix. Generally, 5 or 6 sack is required in a foundation wall. Sales contract - A contract between a buyer and seller which should explain: (1) What the purchase includes, (2) What guarantees there are, (3) When the buyer can move in, (4) What the closing costs are, and (5) What recourse the parties have if the contract is not fulfilled or if the buyer cannot get a mortgage commitment at the agreed upon time. Sand float finish- Lime that is mixed with sand, resulting in a textured finish on a wall. Sanitary sewer- A sewer system designed for the collection of waste water from the bathroom, kitchen and laundry drains, and is usually not designed to handle storm water. Sash- A single light frame containing one or more lights of glass. The frame that holds the glass in a window, often the movable part of the window. Sash balance- A device, usually operated by a spring and designed to hold a single hung window vent up and in place Saturated felt- A felt which is impregnated with tar or asphalt. Schedule (window, door, mirror)- A table on the blueprints that list the sizes, quantities and locations of the windows, doors and mirrors. Scrap out- The removal of all drywall material and debris after the home is "hung out" (installed) with drywall. Scratch coat- The first coat of plaster, which is scratched to form a bond for a second coat. Screed, concrete- To level off concrete to the correct elevation during a concrete pour.

Screed, plaster- A small strip of wood, usually the thickness of the plaster coat, used as a guide for plastering. Scribing- Cutting and fitting woodwork to an irregular surface. Scupper- (1) An opening for drainage in a wall, curb or parapet. (2) The drain in a downspout or flat roof, usually connected to the downspout. Sealer- A finishing material, either clear or pigmented, that is usually applied directly over raw wood for the purpose of sealing the wood surface. Seasoning- Drying and removing moisture from green wood in order to improve its usability. Self-sealing shingles- Shingles containing factory-applied strips or spots of self-sealing adhesive. Semigloss paint or enamel- A paint or enamel made so that its coating, when dry, has some luster but is not very glossy. Bathrooms and kitchens are normally painted semi-gloss Septic system- An on site waste water treatment system. It usually has a septic tank which promotes the biological digestion of the waste, and a drain field which is designed to let the left over liquid soak into the ground. Septic systems and permits are usually sized by the number of bedrooms in a house. Service entrance panel- Main power cabinet where electricity enters a home wiring system. Service equipment- Main control gear at the service entrance, such as circuit breakers, switches, and fuses. Service lateral- Underground power supply line. Setback Thermostat- A thermostat with a clock which can be programmed to come on or go off at various temperatures and at different times of the day/week. Usually used as the heating or cooling system thermostat. Settlement- Shifts in a structure, usually caused by freeze-thaw cycles underground.

Sewage ejector- A pump used to 'lift' waste water to a gravity sanitary sewer line. Usually used in basements and other locations which are situated bellow the level of the side sewer. Sewer lateral- The portion of the sanitary sewer which connects the interior waste water lines to the main sewer lines. The side sewer is usually buried in several feet of soil and runs from the house to the sewer line. It is usually 'owned' by the sewer utility, must be maintained by the owner and may only be serviced by utility approved contractors. Sometimes called side sewer. Sewer stub- The junction at the municipal sewer system where the home's sewer line is connected. Sewer tap- The physical connection point where the home's sewer line connects to the main municipal sewer line. Shake- A wood roofing material, normally cedar or redwood. Produced by splitting a block of the wood along the grain line. Modern shakes are sometimes machine sawn on one side. See shingle. Shear block- Plywood that is face nailed to short (2 X 4's or 2 X 6's) wall studs (above a door or window, for example). This is done to prevent the wall from sliding and collapsing. Sheathing, sheeting- The structural wood panel covering, usually OSB or plywood, used over studs, floor joists or rafters/trusses of a structure. Shed roof- A roof containing only one sloping plane. Sheet metal work- All components of a house employing sheet metal, such as flashing, gutters, and downspouts. Sheet metal duct work- The heating system. Usually round or rectangular metal pipes and sheet metal (for Return Air) and installed for distributing warm (or cold) air from the furnace to rooms in the home. Sheet rock- Drywall-Wall board or gypsum- A manufactured panel made out of gypsum plaster and encased in a thin cardboard. Usually 1/2" thick and 4' x 8' or 4' x 12' in size. The 'joint compound'. 'Green board' type drywall has a greater resistance to moisture than regular (white) plasterboard and is used in bathrooms and other "wet areas".

Shim- A small piece of scrap lumber or shingle, usually wedge shaped, which when forced behind a furring strip or framing member forces it into position. Also used when installing doors and placed between the door jamb legs and 2 X 4 door trimmers. Metal shims are wafer 1 1/2" X 2" sheet metal of various thickness' used to fill gaps in wood framing members, especially at bearing point locations. Shingles- Roof covering of asphalt. asbestos, wood, tile, slate, or other material cut to stock lengths, widths, and thickness'. Shingles, siding- Various kinds of shingles, used over sheathing for exterior wall covering of a structure. Short circuit- A situation that occurs when hot and neutral wires come in contact with each other. Fuses and circuit breakers protect against fire that could result from a short. Shutter- Usually lightweight louvered decorative frames in the form of doors located on the sides of a window. Some shutters are made to close over the window for protection. Side sewer- The portion of the sanitary sewer which connects the interior waste water lines to the main sewer lines. The side sewer is usually buried in several feet of soil and runs from the house to the sewer line. It is usually 'owned' by the sewer utility, must be maintained by the owner and may only be serviced by utility approved contractors. Sometimes called sewer lateral. Siding- The finished exterior covering of the outside walls of a frame building. Siding, (lap siding)- Slightly wedge-shaped boards used as horizontal siding in a lapped pattern over the exterior sheathing. Varies in butt thickness from ½ to ¾ inch and in widths up to 12". Sill- (1) The 2 X 4 or 2 X 6 wood plate framing member that lays flat against and bolted to the foundation wall (with anchor bolts) and upon which the floor joists are installed. Normally the sill plate is treated lumber. (2) The member forming the lower side of an opening, as a door sill or window sill. Sill cock- An exterior water faucet (hose bib).

Sill plate (mudsill)- Bottom horizontal member of an exterior wall frame which rests on top a foundation, sometimes called mudsill. Also sole plate, bottom member of an interior wall frame. Sill seal- Fiberglass or foam insulation installed between the foundation wall and sill (wood) plate. Designed to seal any cracks or gaps. Single hung window- A window with one vertically sliding sash or window vent. Skylight- A more or less horizontal window located on the roof of a building. Slab, concrete- Concrete pavement, i.e. driveways, garages, and basement floors. Slab, door- A rectangular door without hinges or frame. Slab on grade- A type of foundation with a concrete floor which is placed directly on the soil. The edge of the slab is usually thicker and acts as the footing for the walls. Slag- Concrete cement that sometimes covers the vertical face of the foundation void material. Sleeper- Usually, a wood member embedded in concrete, as in a floor, that serves to support and to fasten the subfloor or flooring. Sleeve(s)- Pipe installed under the concrete driveway or sidewalk, and that will be used later to run sprinkler pipe or low voltage wire. Slope- The incline angle of a roof surface, given as a ratio of the rise (in inches) to the run (in feet). See also pitch. Slump- The "wetness" of concrete. A 3 inch slump is dryer and stiffer than a 5 inch slump. Soffit- The area below the eaves and overhangs. The underside where the roof overhangs the walls. Usually the underside of an overhanging cornice.

Soil pipe- A large pipe that carries liquid and solid wastes to a sewer or septic tank. Soil stack- A plumbing vent pipe that penetrates the roof. Sole plate- The bottom, horizontal framing member of a wall that's attached to the floor sheeting and vertical wall studs. Solid bridging- A solid member placed between adjacent floor joists near the center of the span to prevent joists or rafters from twisting. Sonotube- Round, large cardboard tubes designed to hold wet concrete in place until it hardens. Sound attenuation- Sound proofing a wall or subfloor, generally with fiberglass insulation. Space heat- Heat supplied to the living space, for example, to a room or the living area of a building. Spacing- The distance between individual members or shingles in building construction. Span- The clear distance that a framing member carries a load without support between structural supports. The horizontal distance from eaves to eaves. Spec home- A house built before it is sold. The builder speculates that he can sell it at a profit. Specifications or Specs- A narrative list of materials, methods, model numbers, colors, allowances, and other details which supplement the information contained in the blue prints. Written elaboration in specific detail about construction materials and methods. Written to supplement working drawings. Splash block- Portable concrete (or vinyl) channel generally placed beneath an exterior sill cock (water faucet) or downspout in order to receive roof drainage from downspouts and to divert it away from the building.

Square- A unit of measure-100 square feet-usually applied to roofing and siding material. Also, a situation that exists when two elements are at right angles to each other. Also a tool for checking this. Square-tab shingles- Shingles on which tabs are all the same size and exposure. Squeegie- Fine pea gravel used to grade a floor (normally before concrete is placed). Stack (trusses)- To position trusses on the walls in their correct location. Standard practices of the trade(s)- One of the more common basic and minimum construction standards. This is another way of saying that the work should be done in the way it is normally done by the average professional in the field. Starter strip- Asphalt roofing applied at the eaves that provides protection by filling in the spaces under the cutouts and joints of the first course of shingles. Stair carriage or stringer- Supporting member for stair treads. Usually a 2 X 12 inch plank notched to receive the treads; sometimes called a "rough horse." Stair landing- A platform between flights of stairs or at the termination of a flight of stairs. Often used when stairs change direction. Normally no less than 3 ft. X 3 ft. square. Stair rise- The vertical distance from stair tread to stair tread (and not to exceed 7 ½"). Static vent- A vent that does not include a fan. STC (Sound Transmission Class)- The measure of sound stopping of ordinary noise. Steel inspection- A municipal and/or engineers inspection of the concrete foundation wall, conducted before concrete is poured into the foundation panels. Done to insure that the rebar (reinforcing bar), rebar nets, void

material, beam pocket plates, and basement window bucks are installed and wrapped with rebar and complies with the foundation plan. Step flashing- Flashing application method used where a vertical surface meets a sloping roof plane. 6" X 6" galvanized metal bent at a 90 degree angle, and installed beneath siding and over the top of shingles. Each piece overlaps the one beneath it the entire length of the sloping roof (step by step). Stick built- A house built without prefabricated parts. Also called conventional building. Stile- An upright framing member in a panel door. Stool- The flat molding fitted over the window sill between jambs and contacting the bottom rail of the lower sash. Also another name for toilet. Stop box- Normally a cast iron pipe with a lid (@ 5" in diameter) that is placed vertically into the ground, situated near the water tap in the yard, and where a water cut-off valve to the home is located (underground). A long pole with a special end is inserted into the curb stop to turn off/on the water. Stop Order- A formal, written notification to a contractor to discontinue some or all work on a project for reasons such as safety violations, defective materials or workmanship, or cancellation of the contract. Stops- Moldings along the inner edges of a door or window frame. Also valves used to shut off water to a fixture. Stop valve- A device installed in a water supply line, usually near a fixture, that permits an individual to shut off the water supply to one fixture without interrupting service to the rest of the system. Storm sash or storm window-. An extra window usually placed outside of an existing one, as additional protection against cold weather. Storm sewer- A sewer system designed to collect storm water and is separated from the waste water system. Story- That part of a building between any floor or between the floor and roof.

Strike- The plate on a door frame that engages a latch or dead bolt. String, stringer- A timber or other support for cross members in floors or ceilings. In stairs, the supporting member for stair treads. Usually a 2 X 12 inch plank notched to receive the treads Strip flooring- Wood flooring consisting of narrow, matched strips. Structural floor- A framed lumber floor that is installed as a basement floor instead of concrete. This is done on very expansive soils. Stub, stubbed- To push through. Stucco- Refers to an outside plaster finish made with Portland cement as its base. Stud- A vertical wood framing member, also referred to as a wall stud, attached to the horizontal sole plate below and the top plate above. Normally 2 X 4's or 2 X 6's, 8' long (sometimes 92 5/8"). One of a series of wood or metal vertical structural members placed as supporting elements in walls and partitions. Stud framing- A building method that distributes structural loads to each of a series of relatively lightweight studs. Contrasts with post-and-beam. Stud shoe- A metal, structural bracket that reinforces a vertical stud. Used on an outside bearing wall where holes are drilled to accommodate a plumbing waste line. Subfloor- The framing components of a floor to include the sill plate, floor joists, and deck sheeting over which a finish floor is to be laid. Sump- Pit or large plastic bucket/barrel inside the home designed to collect ground water from a perimeter drain system. Sump pump- A submersible pump in a sump pit that pumps any excess ground water to the outside of the home. Suspended ceiling- A ceiling system supported by hanging it from the overhead structural framing.

Sway brace- Metal straps or wood blocks installed diagonally on the inside of a wall from bottom to top plate, to prevent the wall from twisting, racking, or falling over "domino" fashion. Switch- A device that completes or disconnects an electrical circuit.

T & G, tongue and groove- A joint made by a tongue (a rib on one edge of a board) that fits into a corresponding groove in the edge of another board to make a tight flush joint. Typically, the subfloor plywood is T & G. Tab - The exposed portion of strip shingles defined by cutouts. Tail beam- A relatively short beam or joist supported in a wall on one end and by a header at the other. Take off- The material necessary to complete a job. Taping- The process of covering drywall joints with paper tape and joint compound. T bar- Ribbed, "T" shaped bars with a flat metal plate at the bottom that are driven into the earth. Normally used chain link fence poles, and to mark locations of a water meter pit. Teco- Metal straps that are nailed and secure the roof rafters and trusses to the top horizontal wall plate. Sometimes called a hurricane clip. Tee- A "T" shaped plumbing fitting. Tempered- Strengthened. Tempered glass will not shatter nor create shards, but will "pelletize" like an automobile window. Required in tub and shower enclosures and locations, entry door glass and sidelight glass, and in a windows when the window sill is less than 16" to the floor. Termites- Wood eating insects that superficially resemble ants in size and general appearance, and live in colonies. Termite shield- A shield, usually of galvanized metal, placed in or on a foundation wall or around pipes to prevent the passage of termites. Terra cotta- A ceramic material molded into masonry units. Thermoply ™- Exterior laminated sheathing nailed to the exterior side of the exterior walls. Normally ¼ " thick, 4 X 8 or 4 x 10 sheets with an aluminumized surface.

Thermostat- A device which relegates the temperature of a room or building by switching heating or cooling equipment on or off. Three-dimensional shingles- Laminated shingles. Shingles that have added dimensionality because of extra layers or tabs, giving a shake-like appearance. May also be called "architectural shingles". Threshold- The bottom metal or wood plate of an exterior door frame. Generally they are adjustable to keep a tight fit with the door slab. Time and materials contract- A construction contract which specifies a price for different elements of the work such as cost per hour of labor, overhead, profit, etc. A contract which may not have a maximum price, or may state a 'price not to exceed'. Tinner- Another name for the heating contractor. Tip up- The downspout extension that directs water (from the home's gutter system) away from the home. They typically swing up when mowing the lawn, etc. Title- Evidence (usually in the form of a certificate or deed) of a person's legal right to ownership of a property. TJI or TJ- Manufactured structural building component resembling the letter "I". Used as floor joists and rafters. I-joists include two key parts: flanges and webs. The flange or from of the I joist may be made of laminated veneer lumber or dimensional lumber, usually formed into a 1 ½" width. The web or center of the I-joist is commonly made of plywood or oriented strand board (OSB). Large holes can be cut in the web to accommodate duct work and plumbing waste lines. I-joists are available in lengths up to 60'' long. Toenailing- To drive a nail in at a slant. Method used to secure floor joists to the plate. Top chord- The upper or top member of a truss. Top plate- Top horizontal member of a frame wall supporting ceiling joists, rafters, or other members.

Transmitter (garage door)- The small, push button device that causes the garage door to open or close. Trap- A plumbing fitting that holds water to prevent air, gas, and vermin from backing up into a fixture. Tread- The walking surface board in a stairway on which the foot is placed. Treated lumber- A wood product which has been impregnated with chemical pesticides such as CCA (Chromated Copper Arsenate) to reduce damage from wood rot or insects. Often used for the portions of a structure which are likely to be in contact with soil and water. Wood may also be treated with a fire retardant. Trim (plumbing, heating, electrical)- The work that the "mechanical" contractors perform to finish their respective aspects of work, and when the home is nearing completion and occupancy. Trim- Interior- The finish materials in a building, such as moldings applied around openings (window trim, door trim) or at the floor and ceiling of rooms (baseboard, cornice, and other moldings). Also, the physical work of installing interior doors and interior woodwork, to include all handrails, guardrails, stair way balustrades, mantles, light boxes, base, door casings, cabinets, countertops, shelves, window sills and aprons, etc. Exterior- The finish materials on the exterior a building, such as moldings applied around openings (window trim, door trim), siding, windows, exterior doors, attic vents, crawl space vents, shutters, etc. Also, the physical work of installing these materials Trimmer- The vertical stud that supports a header at a door, window, or other opening. Truss- An engineered and manufactured roof support member with "zigzag" framing members. Does the same job as a rafter but is designed to have a longer span than a rafter. Tub trap- Curved, "U" shaped section of a bath tub drain pipe that holds a water seal to prevent sewer gasses from entering the home through tubs water drain.

Turnkey- A term used when the subcontractor provides all materials (and labor) for a job. Turpentine- A petroleum, volatile oil used as a thinner in paints and as a solvent in varnishes

UL (Underwriters' Laboratories)- An independent testing agency that checks electrical devices and other components for possible safety hazards. Undercoat- A coating applied prior to the finishing or top coats of a paint job. It may be the first of two or the second of three coats. Sometimes called the Prime coat. Underground plumbing- The plumbing drain and waste lines that are installed beneath a basement floor. Underlayment- A ¼" material placed over the subfloor plywood sheeting and under finish coverings, such as vinyl flooring, to provide a smooth, even surface. Also a secondary roofing layer that is waterproof or water-resistant, installed on the roof deck and beneath shingles or other roof-finishing layer. Union- A plumbing fitting that joins pipes end-to-end so they can be dismantled. Utility easement- The area of the earth that has electric, gas, or telephone lines. These areas may be owned by the homeowner, but the utility company has the legal right to enter the area as necessary to repair or service the lines.

Valley- The "V" shaped area of a roof where two sloping roofs meet. Water drains off the roof at the valleys. Valley flashing- Sheet metal that lays in the "V" area of a roof valley. Valuation- An inspection carried out for the benefit of the mortgage lender to ascertain if a property is a good security for a loan. Valuation fee- Th fee paid by the prospective borrower for the lender's inspection of the property. Normally paid upon loan application. Vapor barrier- A building product installed on exterior walls and ceilings under the drywall and on the warm side of the insulation. It is used to retard the movement of water vapor into walls and prevent condensation within them. Normally, polyethylene plastic sheeting is used. Variable rate- An interest rate that will vary over the term of the loan. Veneer- Extremely thin sheets of wood. Also a thin slice of wood or brick or stone covering a framed wall. Vent- A pipe or duct which allows the flow of air and gasses to the outside. Also, another word for the moving glass part of a window sash, i.e. window vent. Vermiculite- A mineral used as bulk insulation and also as aggregate in insulating and acoustical plaster and in insulating concrete floors. Veterans Administration (VA)- A federal agency that insures mortgage loans with very liberal down payment requirements for honorably discharged veterans and their surviving spouses. Visqueen- A 4 mil or 6 mil plastic sheeting. Void- Cardboard rectangular boxes that are installed between the earth (between caissons) and the concrete foundation wall. Used when expansive soils are present. Voltage- A measure of electrical potential. Most homes are wired with 110 and 220 volt lines. The 110 volt power is used for lighting and most of the other circuits. The 220 volt power is usually used for the kitchen range, hot

water heater and dryer.

Wafer board - A manufactured wood panel made out of 1"- 2" wood chips and glue. Often used as a substitute for plywood in the exterior wall and roof sheathing. Walk-Through- A final inspection of a home before "Closing" to look for and document problems that need to be corrected. Wall out- When a painter pray paints the interior of a home. Warping- Any distortion in a material. Warranty- In construction there are two general types of warranties. One is provided by the manufacturer of a product such as roofing material or an appliance. The second is a warranty for the labor. For example, a roofing contract may include a 20 year material warranty and a 5 year labor warranty. Many new homebuilders provide a one year warranty. Any major issue found during the first year should be communicated to the builder immediately. Small items can be saved up and presented to the builder for correction periodically through the first year after closing. Waste pipe and vent- Plumbing plastic pipe that carries waste water to the municipal sewage system. Water board- Water resistant drywall to be used in tub and shower locations. Normally green or blue colored Water closet- Another name for toilet. Water meter pit (or vault)- The box /cast iron bonnet and concrete rings that contains the water meter. Water-repellent preservative- A liquid applied to wood to give the wood water repellant properties Water table- The location of the underground water, and the vertical distance from the surface of the earth to this underground water. Water tap- The connection point where the home water line connects to the main municipal water system. W C- An abbreviation for water closet (toilet).

Weatherization- Work on a building exterior in order to reduce energy consumption for heating or cooling. Work involving adding insulation, installing storm windows and doors, caulking cracks and putting on weatherstripping. Weatherstrip- Narrow sections of thin metal or other material installed to prevent the infiltration of air and moisture around windows and doors. Weep holes- Small holes in storm window frames that allow moisture to escape. Whole house fan- A fan designed to move air through and out of a home and normally installed in the ceiling. Wind bracing- Metal straps or wood blocks installed diagonally on the inside of a wall from bottom to top plate, to prevent the wall from twisting, racking, or falling over "domino" fashion. Window buck- Square or rectangular box that is installed within a concrete foundation or block wall. A window will eventually be installed in this "buck" during the siding stage of construction Window frame- The stationary part of a window unit; window sash fits into the window frame. Window sash- The operating or movable part of a window; the sash is made of window panes and their border. Wire nut- A plastic device used to connect bare wires together. Wonderboard ™- A panel made out of concrete and fiberglass usually used as a ceramic tile backing material. Commonly used on bathtub decks. Wrapped drywall- Areas that get complete drywall covering, as in the doorway openings of bifold and bipass closet doors.

Y- A "Y" shaped plumbing fitting. Yard of concrete- One cubic yard of concrete is 3' X 3' X 3' in volume, or 27 cubic feet. One cubic yard of concrete will pour 80 square feet of 3 ½" sidewalk or basement/garage floor. Yoke- The location where a home's water meter is sometimes installed between two copper pipes, and located in the water meter pit in the yard.

Z-bar flashing- Bent, galvanized metal flashing that's installed above a horizontal trim board of an exterior window, door, or brick run. It prevents water from getting behind the trim/brick and into the home. Zone- The section of a building that is served by one heating or cooling loop because it has noticeably distinct heating or cooling needs. Also, the section of property that will be watered from a lawn sprinkler system. Zone valve- A device, usually placed near the heater or cooler, which controls the flow of water or steam to parts of the building; it is controlled by a zone thermostat. Zoning- A governmental process and specification which limits the use of a property e.g. single family use, high rise residential use, industrial use, etc. Zoning laws may limit where you can locate a structure. Also see building codes.

Absolute Humidity - The ratio of the mass of water vapor to the volume occupied by a mixture of water vapor and dry air. Absorbent - A material that extracts one or more substances from a fluid (gas or liquid) medium on contact, and which changes physically and/or chemically in the process. The less volatile of the two working fluids in an absorption cooling device. Absorber - The component of a solar thermal collector that absorbs solar radiation and converts it to heat, or, as in a solar photovoltaic device, the material that readily absorbs photons to generate charge carriers (free electrons or holes). Absorption - The passing of a substance or force into the body of another substance. Absorption Chiller - A type of air cooling device that uses absorption cooling to cool interior spaces. Absorption Coefficient - In reference to a solar energy conversion devices, the degree to which a substance will absorb solar energy. In a solar photovoltaic device, the factor by which photons are absorbed as they travel a unit distance through a material. Absorption Cooling - A process in which cooling of an interior space is accomplished by the evaporation of a volatile fluid, which is then absorbed in a strong solution, then desorbed under pressure by a heat source, and then recondensed at a temperature high enough that the heat of condensation can be rejected to a exterior space. Absorption Refrigeration - A system in which a secondary fluid absorbs the refrigerant, releasing heat, then releases the refrigerant and reabsorbs the heat. Ammonia or water is used as the vapor in commercial absorption cycle systems, and water or lithium bromide is the absorber. Absorptivity - In a solar thermal system, the ratio of solar energy striking the absorber that is absorbed by the absorber to that of solar energy striking a black body (perfect absorber) at the same temperature. The absorptivity of a material is numerically equal to its emissivity.

Accumulator - A component of a heat pump that stores liquid and keeps it from flooding the compressor. The accumulator takes the strain off the compressor and improves the reliability of the system. Acid Rain - A term used to describe precipitation that has become acidic (low pH) due to the emission of sulfur oxides from fossil fuel burning power plants. Active Cooling - The use of mechanical heat pipes or pumps to transport heat by circulating heat transfer fluids. Active Power - The power (in Watts) used by a device to produce useful work. Also called input power. Active Solar Heating Systems - A solar water or space-heating system that use pumps or fans to circulate the heat-transfer fluid from the solar collectors to a storage tank subsystem. Adiabatic - Without loss or gain of heat to a system. An adiabatic change is a change in volume and pressure of a parcel of gas without an exchange of heat between the parcel and its surroundings. In reference to a steam turbine, the adiabatic efficiency is the ratio of the work done per pound of steam, to the heat energy released and theoretically capable of transformation into mechanical work during the adiabatic expansion of a unit weight of steam. Adjustable Speed Drive - An electronic device that controls the rotational speed of motor-driven equipment such as fans, pumps, and compressors. Speed control is achieved by adjusting the frequency of the voltage applied to the motor. Adobe - A building material made from clay, straw, and water, formed into blocks, and dried; used traditionally in the southwestern U.S. Aerobic Bacteria - Microorganisms that require free oxygen, or air, to live, and that which contribute to the decomposition of organic material in soil or composting systems. Air - The mixture of gases that surrounds the earth and forms its atmosphere, composed of, by volume, 21 percent oxygen, 78 percent nitrogen. Air Change - A measure of the rate at which the air in an interior space is replace by outside (or conditioned) air by ventilation and

infiltration; usually measured in cubic feet per time interval (hour), divided by the volume of air in the room. Air Collector - In solar heating systems, a type of solar collector in which air is heated in the collector. Air Conditioner - A device for conditioning air in an interior space. A Room Air Conditioner is a unit designed for installation in the wall or window of a room to deliver conditioned air without ducts. A Unitary Air Conditioner is composed of one or more assemblies that usually include an evaporator or cooling coil, a compressor and condenser combination, and possibly a heating apparatus. A Central Air Conditioner is designed to provide conditioned air from a central unit to a whole house with fans and ducts. Air Conditioning - The control of the quality, quantity, and temperature-humidity of the air in an interior space. Air Diffuser - An air distribution outlet, typically located in the ceiling, which mixes conditioned air with room air. Air Infiltration Measurement - A building energy auditing technique used to determine and/or locate air leaks in a building shell or envelope. Airlock Entry - A building architectural element (vestibule) with two airtight doors that reduces the amount of air infiltration and exfiltration when the exterior most door is opened. Air Pollution - The presence of contaminants in the air in concentrations that prevent the normal dispersive ability of the air, and that interfere with biological processes and human economics. Air Pollution Control - The use of devices to limit or prevent the release of pollution into the atmosphere. Air Quality Standards - The prescribed level of pollutants allowed in outside or indoor air as established by legislation. Air Register - The component of a combustion device that regulates the amount of air entering the combustion chamber. Air Retarder/Barrier - A material or structural element that inhibits air flow into and out of a building's envelope or shell. This is a

continuous sheet composed of polyethylene, polypropylene, or extruded polystyrene. The sheet is wrapped around the outside of a house during construction to reduce air in-and exfiltration, yet allow water to easily diffuse through it. Air-Source Heat Pump - A type of heat pump that transfers heat from outdoor air to indoor air during the heating season, and works in reverse during the cooling season. Air Space - The area between the layers of glazing (panes) of a window. Airtight Drywall Approach (ADA) - A building construction technique used to create a continuous air retarder that uses the drywall, gaskets, and caulking. Gaskets are used rather than caulking to seal the drywall at the top and bottom. Although it is an effective energy-saving technique, it was designed to keep airborne moisture from damaging insulation and building materials within the wall cavity. Air-to-Air Heat Pump - see Air-Source Heat Pump. Air-to-Water Heat Pump - A type of heat pump that transfers heat in outdoor air to water for space or water heating. Albedo - The ratio of light reflected by a surface to the light falling on it. Alcohol - A group of organic compounds composed of carbon, hydrogen, and oxygen; a series of molecules composed of a hydrocarbon plus a hydroxyl group; includes methanol, ethanol, isopropyl alcohol and others. Algae - Primitive plants, usually aquatic, capable of synthesizing their own food by photosynthesis. Alternating Current - A type of electrical current, the direction of which is reversed at regular intervals or cycles; in the U.S. the standard is 120 reversals or 60 cycles per second; typically abbreviated as AC. Alternative Fuels - A popular term for "non-conventional" transportation fuels derived from natural gas (propane, compressed natural gas, methanol, etc.) or biomass materials (ethanol, methanol).

Alternator - A generator producing alternating current by the rotation of its rotor, and which is powered by a primary mover. Ambient Air - The air external to a building or device. Ambient Temperature - The temperature of a medium, such as gas or liquid, which comes into contact with or surrounds an apparatus or building element. Ammonia - A colorless, pungent, gas (NH3) that is extremely soluble in water, may be used as a refrigerant; a fixed nitrogen form suitable as fertilizer. Amorphous Semiconductor - A non-crystalline semiconductor material that has no long-range order. Ampere - A unit of measure for an electrical current; the amount of current that flows in a circuit at an electromotive force of one Volt and at a resistance of one Ohm. Abbreviated as amp. Amp-Hours - A measure of the flow of current (in amperes) over one hour. Anaerobic Bacteria - Microorganisms that live in oxygen deprived environments. Anaerobic Digestion - The complex process by which organic matter is decomposed by anaerobic bacteria. The decomposition process produces a gaseous byproduct often called "biogas" primarily composed of methane, carbon dioxide, and hydrogen sulfide. Anaerobic Digestor - A device for optimizing the anaerobic digestion of biomass and/or animal manure, and possibly to recover biogas for energy production. Digester types include batch, complete mix, continuous flow (horizontal or plug-flow, multiple-tank, and vertical tank), and covered lagoon. Anaerobic Lagoon - A holding pond for livestock manure that is designed to anaerobically stabilize manure, and may be designed to capture biogas, with the use of an impermeable, floating cover. Anahydrous Ethanol - One hundred percent alcohol; neat ethanol.

Anemometer - An instrument for measuring the force or velocity of wind; a wind guage. Angle of Incidence - In reference to solar energy systems, the angle at which direct sunlight strikes a surface; the angle between the direction of the sun and the perpindicular to the surface. Sunlight with an incident angle of 90 degrees tends to be absorbed, while lower angles tend to be reflected. Angle of Inclination - In reference to solar energy systems, the angle that a solar collector is positioned above horizontal. Angstrom Unit - A unit of length named for A.J. Angstome, a Swedish spectoscopist, used in measuring electromagnetic radiation equal to 0.000,000,01 centimeters. Annual Fuel Utilization Efficiency (AFUE) - The measure of seasonal or annual efficiency of a residential heating furnace or boiler. It takes into account the cyclic on/off operation and associated energy losses of the heating unit as it responds to changes in the load, which in turn is affected by changes in weather and occupant controls. Annual Load Fraction - That fraction of annual energy demand supplied by a solar system. Annual Solar Savings - The annual solar savings of a solar building is the energy savings attributable to a solar feature relative to the energy requirements of a non-solar building. Anode - The positive pole or electrode of an electrolytic cell, vacuum tube, etc. (see also sacrificial anode). Anthracite (coal) - A hard, dense type of coal, that is hard to break, clean to handle, difficult to ignite, and that burns with an intense flame and with the virtual absence of smoke because it contains a high percentage of fixed carbon and a low percentage of volatile matter. Anthropogenic - Referring to alterations in the environment due to the presence or activities of humans. Antifreeze Solution - A fluid, such as methanol or ethylene glycol, added to vehicle engine coolant, or used in solar heating system heat transfer fluids, to protect the systems from freezing.

Antireflection Coating - A thin coating of a material applied to a photovoltaic cell surface that reduces the light reflection and increases light transmission. Aperature - An opening; in solar collectors, the area through which solar radiation is admitted and directed to the absorber. Apparent Day - A solar day; an interval between successive transits of the sun's center across an observer's meridian; the time thus measured is not equal to clock time. Apparent Power (kVA) - This is the voltage-ampere requirement of a device designed to convert electric energy to a non-electrical form. Appliance - A device for converting one form of energy or fuel into useful energy or work. Appliance Energy Efficiency Ratings - The ratings under which specified appliances convert energy sources into useful energy, as determined by procedures established by the U.S. Department of Energy. Appliance Standards- Standards established by the U.S. Congress for energy consuming appliances in the National Appliance Energy Conservation Act (NAECA) of 1987, and as amended in the National Appliance Energy Conservation Amendments of 1988, and the Energy Policy Act of 1992 (EPAct). NAECA established minimum standards of energy efficiency for refrigerators, refrigerator-freezers, freezers, room air conditioners, fluorescent lamp ballasts, incandescent reflector lamps, clothes dryers, clothes washers, dishwashers, kitchen ranges and ovens, pool heaters, television sets (withdrawn in 1995), and water heaters. The EPAct added standards for some fluorescent and incandescent reflector lamps, plumbing products, electric motors, and commercial water heaters and Heating, Ventilation, and Air Conditioning (HVAC) systems. It also allowed for the future development of standards for many other products. The U.S. Department of Energy (DOE) is responsible establishing the standards and the procedures that manufacturers must use to test their models. These procedures are published in the Code of Federal Regulations (10 CFR, Ch. II, Part 430), January 1, 1994 (Federal Register). Argon - A colorless, odorless inert gas sometimes used in the spaces between the panes in energy efficient windows. This gas is used because it will transfer less heat than air. Therefore, it provides

additional protection against conduction and convection of heat over conventional double paned windows. Array (Solar) - Any number of solar photovoltaic modules or solar thermal collectors or reflectors connected together to provide electrical or thermal energy. Ash - The non-combustible residue of a combusted substance composed primarily of alkali and metal oxides. ASHRAE - Abbreviation for the American Society of Heating, Refrigeration, and Air-Conditioning Engineers. ASTM - Abbreviation for the American Society for Testing and Materials, which is responsible for the issue of many standard methods used in the energy industry. Asynchronous Generator - A type of electric generator that produces alternating current that matches an existing power source. Atmospheric Pressure - The pressure of the air at sea level; one standard atmosphere at zero degrees centigrade is equal to 14.695 pounds per square inch (1.033 kilograms per square centimeter). Atrium - An interior court to which rooms open. Attic - The usually unfinished space above a ceiling and below a roof. Attic Fan - A fan mounted on an attic wall used to exhaust warm attic air to the outside. Attic Vent - A passive or mechanical device used to ventilate an attic space, primarily to reduce heat buildup and moisture condensation. Audit (Energy) - The process of determining energy consumption, by various techniques, of a building or facility. Automatic Damper - A device that cuts off the flow of hot or cold air to or from a room as controlled by a thermostat. Automatic (or Remote) Meter Reading System - A system that records the consumption of electricity, gas, water, etc, and sends the data to a central data accumulation device.

Auxillary Energy or System - Energy required to operate mechanical components of an energy system, or a source of energy or energy supply system to back-up another. Availability - Describes the reliability of power plants. It refers to the number of hours that a power plant is available to produce power divided by the total hours in a set time period, usually a year. Available Heat - The amount of heat energy that may be converted into useful energy from a fuel. Average Demand - The demand on, or the power output of, an electrical system or any of its parts over an interval of time, as determined by the total number of kilowatt-hours divided by the units of time in the interval. Average Cost - The total cost of production divided by the total quantity produced. Average Wind Speed (or Velocity) - The mean wind speed over a specified period of time. Avoided Cost - The incremental cost to an electric power producer to generate or purchase a unit of electricity or capacity or both. Axail Fans - Fans in which the direction of the flow of the air from inlet to outlet remains unchanged; includes propeller, tubaxail, and vaneaxial type fans. Axail Flow Compressor - A type of air compressor in which air is compressed in a series of stages as it flows axaily through a decreasing tubular area. Axial Flow Turbine - A turbine in which the flow of a steam or gas is essentially parallel to the rotor axis. Azimuth (Solar) - The angle between true south and the point on the horizon directly below the sun. AWG The abbreviation for American Wire Gauge; the standard for gauging the size of wires (electrical conductors). Awning

An architectural element for shading windows and wall surfaces placed on the exterior of a building; can be fixed or movable.

Backdrafting - The flow of air down a flue/chimney and into a house caused by low indoor air pressure that can occur when using several fans or fireplaces and/or if the house is very tight. Backup Energy System - A reserve appliance; for example, a standby generator for a home or commercial building. Bacteria - Single-celled organisms, free-living or parasitic, that break down the wastes and bodies of dead organisms, making their components available for reuse by other organisms. Baffle - A device, such as a steel plate, used to check, retard, or divert a flow of a material. Bagasse - The fibrous material remaining after the extraction of juice from sugarcane; often burned by sugar mills as a source of energy. Baghouse - An air pollution control device used to filter particulates from waste combustion gases; a chamber containing a bag filter. Balance of System - In a solar energy system, refers to all components other than the collector. In terms of costs, it includes design costs, land, site preparation, system installation, support structures, power conditioning, operation and maintenance costs, indirect storage, and related costs. Balance Point - An outdoor temperature, usually 20 to 45 degrees Fahrenheit, at which a heatpump's output equals the heating demand. Below the balance point, supplementary heat is needed. Baling - A means of reducing the volume of a material by compaction into a bale. Ballast - A device used to control the voltage in a fluorescent lamp. Ballast Efficacy Factor - The measure of the efficiency of fluorescent lamp ballasts. It is the relative light output divided by the power input. Ballast Factor - The ratio of light output of a fluorescent lamp operated on a ballast to the light output of a lamp operated on a standard or reference ballast. Band Gap - In a semiconductor, the energy difference between the highest valence band and the lowest conduction band.

Band Gap Energy - The amount of energy (in electron volts) required to free an outer shell electron from its orbit about the nucleus to a free state, and thus promote it from the valence to the conduction level. Barrel (petroleum) - 42 U.S. gallons (306 pounds of oil, or 5.78 million Btu). Basal Metabolism - The amount of heat given off by a person at rest in a comfortable environment; approximately 50 Btu per hour (Btu/h). Baseboard Radiator - A type of radiant heating system where the radiator is located along an exterior wall where the wall meets the floor. Baseload Capacity - The power output of a power plant that can be continuously produced. Baseload Demand - The minimum demand experienced by a power plant. Baseload Power Plant - A power plant that is normally operated to generate a base load, and that usually operates at a constant load; examples include coal fired and nuclear fueled power plants. Basement - The conditioned or unconditioned space below the main living area or primary floor of a building. Base Power - Power generated by a utility unit that operates at a very high capacity factor. Batch Process - A process for carrying out a reaction in which the reactants are fed in discrete and successive charges. Batt/Blanket - A flexible roll or strip of insulating material in widths suited to standard spacings of building structural members (studs and joists). They are made from glass or rock wool fibers. Blankets are continuous rolls. Batts are pre-cut to four or eight foot lengths. Battery - An energy storage device composed of one or more electrolyte cells. Battery Energy Storage - Energy storage using electrochemical batteries. The three main applications for battery energy storage

systems include spinning reserve at generating stations, load leveling at substations, and peak shaving on the customer side of the meter. Beadwall (TM) - A form of movable insulation that uses tiny polystyrene beads blown into the space between two window panes. Beam Radiation - Solar radiation that is not scattered by dust or water droplets. Bearing Wall - A wall that carries ceiling rafters or roof trusses. Benefits Charge -The addition of a per unit tax on sales of electricity, with the revenue generated used for or to encourage investments in energy efficiency measures and/or renewable energy projects. Bimetal - Two metals of different coefficients of expansion welded together so that the piece will bend in one direction when heated, and in the other when cooled, and can be used to open or close electrical circuits, as in thermostats. Binary Cycle - Combination of two power plant turbine cycles utilizing two different working fluids for power production. The waste heat from the first turbine cycle provides the heat energy for the operation of the second turbine, thus providing higher overall system efficiencies. Binary Cycle Geothermal Plants - Binary cycle systems can be used with liquids at temperatures less than 350 F (177 C). In these systems, the hot geothermal liquid vaporizes a secondary working fluid, which then drives a turbine. Bin Method - A method of predicting heating and/or cooling loads using instantaneous load calculation at different outdoor dry-bulb temperatures, and multiplying the result by the number of hours of occurrence of each temperature. Biochemical Oxygen Demand - The weight of oxygen taken up mainly as a result of the oxidation of the constituents of a sample of water by biological action; expressed as the number of parts per million of oxygen taken up by the sample from water originally saturated with air, usually over a period of five days at 20 degrees centigrade. A standard means of estimating the degree of contamination of water.

Bioconversion - The conversion of one form of energy into another by the action of plants or microorganisms. The conversion of biomass to ethanol, methanol, or methane. Bioenergy - The conversion of the complex carbohydrates in organic material into energy. Biogas - A combustible gas created by anaerobic decomposition of organic material, composed primarily of methane, carbon dioxide, and hydrogen sulfide. Biogasification or biomethanization - The process of decomposing biomass with anaerobic bacteria to produce biogas. Biomass - As defined by the Energy Security Act (PL 96-294) of 1980, "any organic matter which is available on a renewable basis, including agricultural crops and agricultural wastes and residues, wood and wood wastes and residues, animal wastes, municipal wastes, and aquatic plants." Biomass Energy - Energy produced by the conversion of biomass directly to heat or to a liquid or gas that can be converted to energy. Biomass Fuel - Biomass converted directly to energy or converted to liquid or gaseous fuels such as ethanol, methanol, methane, and hydrogen. Biomass Gasification - The conversion of biomass into a gas, by biogasification (see above) or thermal gasification, in which hydrogen is produced from high-temperature gasifying and low-temperature pyrolysis of biomass. Biophotolysis - The action of light on a biological system that results in the dissociation of a substrate, usually water, to produce hydrogen. Blackbody - An ideal substance that absorbs all radiation falling on it, and reflecting nothing. Blower - The device in an air conditioner that distributes the filtered air from the return duct over the cooling coil/heat exchanger. This circulated air is cooled/heated and then sent through the supply duct, past dampers, and through supply diffusers to the living/working space.

Blower Door - A device used by energy auditors to pressurize a building to locate places of air leakage and energy loss. Blown In Insulation (see also Loose Fill) - An insulation product composed of loose fibers or fiber pellets that are blown into building cavities or attics using special pneumatic equipment. Boiler - A vessel or tank where heat produced from the combustion of fuels such as natural gas, fuel oil, or coal is used to generate hot water or steam for applications ranging from building space heating to electric power production or industrial process heat. Boiler Feedwater - The water that is forced into a boiler to take the place of that which is evaporated in the generation of steam. Boiler Horsepower - A unit of rate of water evaporation equal to the evaporation per hour of 34.5 pounds of water at a temperature of 212 degrees Fahrenheit into steam at 212 degrees F. Boiler Pressure - The pressure of the steam or water in a boiler as measured; usually expressed in pounds per square inch gauge (psig). Boiler Rating - The heating capacity of a steam boiler; expressed in Btu per hour (Btu/h), or horsepower, or pounds of steam per hour. Bone (Oven) Dry - In reference to solid biomass fuels, such as wood, having zero moisture content. Bone Dry Unit - A quantity of (solid) biomass fuel equal to 2,400 pounds bone dry. Booster Pump - A pump for circulating the heat transfer fluid in a hydronic heating system. Boot - In heating and cooling system distribution ductwork, the transformation pieces connecting horizontal round leaders to vertical rectangular stacks. Boron - The chemical element commonly used as the dopant in solar photovoltaic device or cell material. Bottled Gas - A generic term for liquefied and pressurized gas, ordinarily butane, propane, or a mixture of the two, contained in a cylinder for domestic use.

Bottoming-cycle - A means to increase the thermal efficiency of a steam electric generating system by converting some waste heat from the condenser into electricity. The heat engine in a bottoming cycle would be a condensing turbine similar in principle to a steam turbine but operating with a different working fluid at a much lower temperature and pressure. Brayton Cycle - A thermodynamic cycle using constant pressure, heat addition and rejection, representing the idealized behavior of the working fluid in a gas turbine type heat engine. Brine - Water saturated or strongly impregnated with salt. British Thermal Unit (Btu) - The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit; equal to 252 calories. Building Energy Ratio - The space-conditioning load of a building. Building Envelope - The structural elements (walls, roof, floor, foundation) of a building that encloses conditioned space; the building shell. Building Heat-Loss Factor - A measure of the heating requirements of a building expressed in Btu per degree-day. Building Orientation - The relationship of a building to true south, as specified by the direction of its longest axis. Building Overall Energy Loss Coefficient-Area Product - The factor, when multiplied by the monthly degree-days, that yields the monthly space heating load. Building Overall Heat Loss Rate - The overall rate of heat loss from a building by means of transmission plus infiltration, expressed in Btu per hour, per degree temperature difference between the inside and outside. Bulb - The transparent or opaque sphere in an electric light that the electric light transmits through. Bulb Turbine - A type of hydroturbine in which the entire generator is mounted inside the water passageway as an integral unit with the

turbine. These installations can offer significant reductions in the size of the powerhouse. Bulk Density - The weight of a material per unit of volume compared to the weight of the same volume of water. Burner Capacity - The maximum heat output (in Btu per hour) released by a burner with a stable flame and satisfactory combustion. Burning Point - The temperature at which a material ignites. Bus (electrical) - An electrical conductor that serves as a common connection for two or more electrical circuits; may be in the form of rigid bars or stranded conductors or cables. Busbar - The power conduit of an electric power plant; the starting point of the electric transmission system. Busbar Cost - The cost of producing electricity up to the point of the powerplant busbar. Bypass - An alternative path. In a heating duct or pipe, an alternative path for the flow of the heat transfer fluid from one point to another, as determined by the opening or closing of control valves both in the primary line and the bypass line.

Cage - The component of an electric motor composed of solid bars (of usually copper or aluminum) arranged in a circle and connected to continuous rings at each end. This cage fits inside the stator in an induction motor in channels between laminations, thin flat discs of steel in a ring configuration. Calorie - The amount of heat required to raise the temperature of a unit of water, at or near the temperature of maximum density, one degree Celsius (or Centigrade [C]); expressed as a "small calorie" (the amount of heat required to raise the temperature of 1 gram of water one degree C), or as a "large calorie" or "kilogram calorie" (the amount of heat required to raise one kilogram [1,000 grams] of water one degree C); capitalization of the word calorie indicates a kilogramcalorie. Calorific Value - The heat liberated by the combustion of a unit quantity of a fuel under specific conditions; measured in calories. Candela - A unit of luminous intensity; the magnitude to the candela is such that the luminance of the total radiator, at the temperature of solidification of platinum, is 60 candelas per square centimeter. Candle Power - The illuminating power of a standard candle employed as a unit for determining the illuminating quality of an illuminant. Capability - The maximum load that a generating unit, power plant, or other electrical apparatus can carry under specified conditions for a given period of time, without exceeding its approved limits of temperature and stress. Capability Margin - The difference between net electrical system capability and system maximum load requirements (peak load); the margin of capability available to provide for scheduled maintenance, emergency outages, system operating requirements and unforeseen loads. Capacitance - A measure of the electrical charge of a capacitor consisting of two plates separated by an insulating material. Capacitor - An electrical device that adjusts the leading current of an applied alternating current to balance the lag of the circuit to provide a high power factor.

Capacity - The load that a power generation unit or other electrical apparatus or heating unit is rated by the manufacture to be able to meet or supply. Capacity (Condensing Unit) - The refrigerating effect in Btu/h produced by the difference in total enthalpy between a refrigerant liquid leaving the unit and the total enthalpy of the refrigerant vapor entering it. Generally measured in tons or Btu/h. Capacity (Effective, of a motor) - The maximum load that a motor is capable of supplying. Capacity (Heating, of a material) - The amount of heat energy needed to raise the temperature of a given mass of a substance by one degree Celsius. The heat required to raise the temperature of 1 kg of water by 1 degree Celsius is 4186 Joules. Capacity Factor - The ratio of the average load on (or power output of) a generating unit or system to the capacity rating of the unit or system over a specified period of time. Capital Costs - The amount of money needed to purchase equipment, buildings, tools, and other manufactured goods that can be used in production. Carbon Dioxide - A colorless, odorless noncombustible gas with the formula CO2 that is present in the atmosphere. It is formed by the combustion of carbon and carbon compounds (such as fossil fuels and biomass), by respiration, which is a slow combustion in animals and plants, and by the gradual oxidation of organic matter in the soil. Carbon Monoxide - A colorless, odorless but poisonous combustible gas with the formula CO. Carbon monoxide is produced in the incomplete combustion of carbon and carbon compounds such as fossil fuels (i.e. coal, petroleum) and their products (e.g. liquefied petroleum gas, gasoline), and biomass. Carbon Zinc Cell Battery - A cell produces electric energy by the galvanic oxidation of carbon; commonly used in household appliances. Carnot Cycle - An ideal heat engine (conceived by Sadi Carnot) in which the sequence of operations forming the working cycle consists of isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression back to its initial state.

Catalytic Converter - An air pollution control device that removes organic contaminants by oxidizing them into carbon dioxide and water through a chemical reaction using a catalysis, which is a substance that increases (or decreases) the rate of a chemical reaction without being changed itself; required in all automobiles sold in the United State, and used in some types of heating appliances. Cathedral Ceiling/Roof - A type of ceiling and roof assembly that has no attic. Cathode - The negative pole or electrode of an electrolytic cell, vacuum tube, etc., where electrons enter (current leaves) the system; the opposite of an anode. Cathode Disconnect Ballast - An electromagnetic ballast that disconnects a lamp's electrode heating circuit once is has started; often called "low frequency electronic" ballasts. Cathodic Protection - A method of preventing oxidation of the exposed metal in structures by imposing between the structure and the ground a small electrical voltage. Caulking - A material used to seal areas of potential air leakage into or out of a building envelope. Ceiling - The downward facing structural element that is directly opposite the floor. Ceiling Fan - A mechanical device used for air circulation and to provide cooling. Cell - A component of a electrochemical battery. A 'primary' cell consists of two dissimilar elements, known as 'electrodes,' immersed in a liquid or paste known as the 'electrolyte.' A direct current of 1-1.5 volts will be produced by this cell. A 'secondary' cell or accumulator is a similar design but is made useful by passing a direct current of correct strength through it in a certain direction. Each of these cells will produce 2 volts; a 12 volt car battery contains six cells. Cellulase - An enzyme complex, produced by fungi and bacteria, capable of decomposing cellulose into small fragments, primarily glucose.

Cellulose - The fundamental constituent of all vegetative tissue; the most abundant material in the world. Cellulose Insulation- A type of insulation composed of waste newspaper, cardboard, or other forms of waste paper. Central Heating System - A system where heat is supplied to areas of a building from a single appliance through a network of ducts or pipes. Central Power Plant - A large power plant that generates power for distribution to multiple customers. Central Receiver Solar Power Plants - Also known as "power towers," these use fields of two-axis tracking mirrors known as heliostats. Each heliostat is individually positioned by a computer control system to reflect the sun's rays to a tower-mounted thermal receiver. The effect of many heliostats reflecting to a common point creates the combined energy of thousands of suns, which produces high-temperature thermal energy. In the receiver, molten nitrate salts absorb the heat energy. The hot salt is then used to boil water to steam, which is sent to a conventional steam turbine-generator to produce electricity. Cetane Number - A measure of a fuel's (liquid) ease of self-ignition. Char - A byproduct of low-temperature carbonization of a solid fuel. Charcoal - A material formed from the incomplete combustion or destructive distillation (carbonization) of organic material in a kiln or retort, and having a high energy density, being nearly pure carbon. (If produced from coal, it is coke.) Used for cooking, the manufacture of gunpowder and steel (notably in Brazil), as an absorbent and decolorising agent, and in sugar refining and solvent recovery. Charge Carrier - A free and mobile conduction electron or hole in a semiconductor. Chemical Energy - The energy liberated in a chemical reaction, as in the combustion of fuels. Chemical Vapor Deposition (CVD) - A method of depositing thin semiconductor films used to make certain types of solar photovoltaic devices. With this method, a substrate is exposed to one or more

vaporized compounds, one or more of which contain desirable constituents. A chemical reaction is initiated, at or near the substrate surface, to produce the desired material that will condense on the substrate. Chiller - A device for removing heat from a gas or liquid stream for air conditioning/cooling. Chimney - A masonry or metal stack that creates a draft to bring air to a fire and to carry the gaseous byproducts of combustion safely away. Chlorofluorocarbon (CFC) - A family of chemicals composed primarily of carbon, hydrogen, chlorine, and fluorine whose principal applications are as refrigerants and industrial cleansers and whose principal drawback is the tendency to destroy the Earth's protective ozone layer. Circuit - A device, or system of devices, that allows electrical current to flow through it and allows voltage to occur across positive and negative terminals. Circuit Breaker - A device used to interrupt or break an electrical circuit when an overload condition exists; usually installed in the positive circuit; used to protect electrical equipment. Circuit Lag - As time increases from zero at the terminals of an inductor, the voltage comes to a particular value on the sine function curve ahead of the current. The voltage reaches its negative peak exactly 90 degrees before the current reaches its negative peak thus the current lags behind by 90 degrees. Circulating Fluidized Bed - A type of furnace or reactor in which the emission of sulfur compounds is lowered by the addition of crushed limestone in the fluidized bed thus obviating the need for much of the expensive stack gas clean-up equipment. The particles are collected and recirculated, after passing through a conventional bed, and cooled by boiler internals. Cleavage of Lateral Epitaxial Films for Transfer (CLEFT) - A process for making inexpensive Galium Arsenide (GaAs)photovoltaic cells in which a thin film of GaAs is grown atop a thick, single-crystal GaAs (or other suitable material) substrate and then is cleaved from

the substrate and incorporated into a cell, allowing the substrate to be reused to grow more thin-film GaAs. Clerestory - A window located high in a wall near the eaves that allows daylight into a building interior, and may be used for ventilation and solar heat gain. Climate - The prevailing or average weather conditions of a geographic region. Climate Change - A term used to describe short and long-term affects on the Earth's climate as a result of human activities such as fossil fuel combustion and vegetation clearing and burning. Close Coupled - An energy system in which the fuel production equipment is in close proximity, or connected to, the fuel using equipment. Closed Cycle - A system in which a working fluid is used over and over without introduction of new fluid, as in a hydronic heating system or mechanical refrigeration system. Closed-Loop - A type of heating system in which the heat transfer fluid circulates from the heating component to a heat exchanger that is immersed in a heat storage media, passing its heat to the storage media without physically contacting it. Closed Loop Biomass - As defined by the Comprehensive National Energy Act of 1992 (or the Energy Policy Act; EPAct): any organic matter from a plant which is planted for the exclusive purpose of being used to produce energy." This does not include wood or agricultural wastes or standing timber. Codes - Legal documents that regulate construction to protect the health, safety, and welfare of people. Codes establish minimum standards but do not guarantee efficiency or quality. Coefficient of Heat Transmission (U-Value) - A value that describes the ability of a material to conduct heat. The number of Btu that flow through 1 square foot of material, in one hour. It is the reciprocal of the R-Value (U-Value = 1/R-Value). Coefficient of Performance (COP) - A ratio of the work or useful energy output of a system versus the amount of work or energy

inputted into the system as determined by using the same energy equivalents for energy in and out. Is used as a measure of the steady state performance or energy efficiency of heating, cooling, and refrigeration appliances. The COP is equal to the Energy Efficiency Ratio (EER) divided by 3.412. The higher the COP, the more efficient the device. Coefficient of Utilization (CU) - A term used for lighting appliances; the ratio of lumens received on a flat surface to the light output, in lumens, from a lamp; used to evaluate the effectiveness of luminaries in delivering light. Coincidence Factor - The ratio of the coincident, maximum demand or two or more loads to the sum of their noncoincident maximum demand for a given period; the reciprocal of the diversity factor, and is always less than or equal to one. Coincident Demand - The demand of a consumer of electricity at the time of a power supplier's peak system demand. Cofiring - The use of two or more different fuels (e.g. wood and coal) simultaneously in the same combustion chamber of a power plant. Cogeneration - The generation of electricity or shaft power by an energy conversion system and the concurrent use of rejected thermal energy from the conversion system as an auxiliary energy source. Cogenerator - A class of energy producer that produces both heat and electricity from a single fuel. Coil - As a component of a heating or cooling appliance, rows of tubing or pipe with fins attached through which a heat transfer fluid is circulated and to deliver heat or cooling energy to a building. Cold Night Sky - The low effective temperature of the sky on a clear night. Collector - The component of a solar energy heating system that collects solar radiation, and that contains components to absorb solar radiation and transfer the heat to a heat transfer fluid (air or liquid). Collector Efficiency - The ratio of solar radiation captured and transfered to the collector (heat transfer) fluid.

Collector Fluid - The fluid, liquid (water or water/antifreeze solution) or air, used to absorb solar energy and transfer it for direct use, indirect heating of interior air or domestic water, and/or to a heat storage medium. Collector Tilt - The angle that a solar collector is positioned from horizontal. Color Rendering or Rendition - A measure of the ability of a light source to show colors, based on a color rendering index. Color Rendition (Rendering) Index (CRI) - A measure of light quality. The maximum CRI value of 100 is given to natural daylight and incandescent lighting. The closer a lamp's CRI rating is to 100, the better its ability to show true colors to the human eye. Color Temperature - A measure of the quality of a light source by expressing the color appearance correlated with a black body. Combined-Cycle Power Plant - A power plant that uses two thermodynamic cycles to achieve higher overall system efficiency; e.g.: the heat from a gas-fired combustion turbine is used to generate steam for heating or to operate a steam turbine to generate additional electricity. Combustion - The process of burning; the oxidation of a material by applying heat, which unites oxygen with a material or fuel. Combustion Air - Air that provides the necessary oxygen for complete, clean combustion and maximum heating value. Combustion Chamber - Any wholly or partially enclosed space in which combustion takes place. Combustion Gases - The gaseous byproducts of the combustion of a fuel. Combustion Power Plant - A power plant that generates power by combusting a fuel. Combustion Turbine - A turbine that generates power from the combustion of a fuel.

Commercial Building - A building with more than 50 percent of its floorspace used for commercial activities, which include stores, offices, schools, churches, libraries, museums, health care facilities, warehouses, and government buildings except those on military bases. Commercial Sector - Consists of businesses that are not engaged in transportation or manufacturing or other types of industrial activities. Standard Industrial Classification (SIC) codes for commercial establishments are 50 through 87, 89, and 91 through 97. Comfort Zone - A frequently used room or area that is maintained at a more comfortable level than the rest of the house; also known as a "warm room." Commissioning - The process by which a power plant, apparatus, or building is approved for operation based on observed or measured operation that meets design specifications. Compact Fluorescent - A smaller version of standard fluorescent lamps which can directly replace standard incandescent lights. These lights consist of a gas filled tube, and a magnetic or electronic ballast. Complete Mix Digester - A type of anaerobic digester that has a mechanical mixing system and where temperature and volume are controlled to maximize the anaerobic digestion process for biological waste treatment, methane production, and odor control. Composting - The process of degrading organic material (biomass) by microorganisms in aerobic conditions. Composting Toilet - A self-contained toilet that use the process of aerobic decomposition (composting) to break down feces into humus and odorless gases. Compound Parabaloid Collector - A form of solar concentrating collector that does not track the sun. Compressed Air Storage - The storage of compressed air in a container for use to operate a prime mover for electricity generation. Compressed Natural Gas (CNG) - Natural gas (methane) that has been compressed to a higher pressure gaseous state by a compressor; used in CNG vehicles.

Compression Chiller - A cooling device that uses mechanical energy to produce chilled water. Compressor - A device used to compress air for mechanical or electrical power production, and in air conditioners, heat pumps, and refrigerators to pressurize the refrigerant and enabling it to flow through the system. Concentrator (Solar) Collector - A solar collector that uses reflective surfaces to concentrate sunlight onto a small area, where it is absorbed and converted to heat or, in the case of solar photovoltaic (PV) devices, into electricity. Concentrators can increase the power flux of sunlight hundreds of times. The principal types of concentrating collectors include: compound parabolic, parabolic trough, fixed reflector moving receiver, fixed receiver moving reflector, fresnel lense, and central receiver. A PV concentrating module uses optical elements (fesnel lense) to increase the amount of sunlight incident onto a PV cell. Concentrating PV modules/arrays must track the sun and use only the direct sunlight because the diffuse portion cannot be focused onto the PV cells. Condensate - The liquid resulting when water vapor contacts a cool surface; also the liquid resulting when a vaporized working fluid (such as a refrigerant) is cooled or depressurized. Condensation - The process by which water in air changes from a vapor to a liquid due to a change in temperature or pressure; occurs when water vapor reaches its dew point (condensation point); also used to express the existence of liquid water on a surface. Condenser - The device in an air conditioner or heat pump in which the refrigerant condenses from a gas to a liquid when it is depressurized or cooled. Condenser Coil - The device in an air conditioner or heat pump through which the refrigerant is circulated and releases heat to the surroundings when a fan blows outside air over the coils. This will return the hot vapor that entered the coil into a hot liquid upon exiting the coil. Condensing Furnace - A type of heating appliance that extracts so much of the available heat content from a combusted fuel that the moisture in the combustion gases condenses before it leaves the furnace. Also this furnace circulates a liquid to cool the furnace's heat

exchanger. The heated liquid may either circulate through a liquid-toair heat exchanger to warm room air, or it may circulate through a coil inside a separate indirect-fired water heater. Condensing Unit - The component of a central air conditioner that is designed to remove heat absorbed by the refrigerant and transfer it outside the conditioned space. Conditioned Space - The interior space of a building that is heated or cooled. Conduction - The transfer of heat through a material by the transfer of kinetic energy from particle to particle; the flow of heat between two materials of different temperatures that are in direct physical contact. Conduction Band - An energy band in a semiconductor in which electrons can move freely in a solid, producing a net transport of charge. Conductivity (Thermal) - This is a positive constant, k, that is a property of a substance and is used in the calculation of heat transfer rates for materials. It is the amount of heat that flows through a specified area and thickness of a material over a specified period of time when there is a temperature difference of one degree between the surfaces of the material. Conductor - The material through which electricity is transmitted, such as an electrical wire, or transmission or distribution line. Conduit - A tubular material used to encase and protect one or more electrical conductors. Congressional (Energy) Committees: House Subcommittee on Energy and Environment - This committee has legislative jurisdiction and general and special oversight and investigative authority on all matters relating to energy and environmental research and development and demonstration. House Water and Power Committee - This committee has oversight over the generation and marketing of electric power from federal water projects by federally charted or Federal RPM authorities, measures and matters concerning water resources planning, compacts

relating to use and apportionment of interstate waters, water rights or power movement programs, measures and matters pertaining to irrigation and reclamation projects and other water resources development programs. Senate Committee on Energy and Natural Resources - This committee has jurisdiction on: coal production, distribution and utilization; energy policy; energy research, conservation, and development; hydroelectric power; irrigation; mineral conservation; nonmilitary development of nuclear energy; solar energy systems; and over territorial possessions, including trusteeships of the United States. Senate Subcommittee on Energy Research, Development, Production and Regulation - This committee has jurisdiction on the oversight and legislative responsibilities for: coal, nuclear, and non-nuclear energy commercialization projects; DOE National Laboratories; global climate change; new technologies research and development; commercialization of new technologies including, solar energy systems; Federal energy conservation programs; energy information; and utility policy. Connected Load - The sum of the ratings of the electricity consuming apparatus connected to a generating system. Connection Charge - An amount paid by a customer for being connected to an electricity supplier's transmission and distribution system. Conservation - To reduce or avoid the consumption of a resource or commodity. Conservation Cost Adjustment - A means of billing electric power consumers to pay for the costs of demand side management/energy conservation measures and programs. (See also Benefits Charge.) Constant Dollars - The value or purchasing power of a dollar in a specified year carried forward or backward. Constant-Speed Wind Turbines - Wind turbines that operate at a constant rotor revolutions per minute (RPM) and are optimized for energy capture at a given rotor diameter at a particular speed in the wind power curve.

Consumption Charge - The part of an energy utility's charge based on actual energy consumed by the customer; the product of the kilowatt-hour rate and the total kilowatt-hours consumed. Contact Resistance - The resistance between metallic contacts and the semiconductor. Continuous Fermentation - A steady-state fermentation process. Contrast - The difference between the brightness of an object compared to that of its immediate background. Convection - The transfer of heat by means of air currents. Conventional Fuel - The fossil fuels: coal, oil, and natural gas. Conventional Heat Pump - This type of heat pump is known as an air-to air system. Conversion Efficiency - The amount of energy produced as a percentage of the amount of energy consumed. Converter - A device for transforming the quality and quantity of electrical energy; also an inverter. Cooling Capacity - The quantity of heat that a cooling appliance is capable of removing from a room in one hour. Cooling Degree Day - A value used to estimate interior air cooling requirements (load) calculated as the number of degrees per day (over a specified period) that the daily average temperature is above 65 degrees Fahrenheit (or some other, specified base temperature). The daily average temperature is the mean of the maximum and minimum temperatures recorded for a specific location for a 24 hour period. Cooling Load - That amount of cooling energy to be supplied (or heat and humidity removed) based on the sensible and latent loads. Cooling Pond - A body of water used to cool the water that is circulated in an electric power plant. Cooling Tower - A structure used to cool power plant water; water is pumped to the top of the tubular tower and sprayed out into the

center, and is cooled by evaporation as it falls, and then is either recycled within the plant or is discharged. Coproducts - The potentially useful byproducts of ethanol fermentation process. Cord (of Wood) - A stack of wood 4 feet by 4 feet by 8 feet. Coulomb - A unit for the quantity of electricity transported in 1 second by a current of 1 ampere. Counterflow Heat Exchanger - A heat exchanger in which two fluids flow in opposite directions for transfer heat energy from one to the other. Covenants - Restrictions on the use of a property. Crawlspace - The unoccupied, and usually unfinished and unconditioned space between the floor, foundation walls, and the slab or ground of a building. Creosote - A liquid byproduct of wood combustion (or distillation) that condenses on the internal surfaces of vents and chimneys, which if not removed regularly, can corrode the surfaces and fuel a chimney fire. Critical Compression Pressure - The highest possible pressure in a fuel-air mixture before spontaneous ignition occurs. Cubic Foot (of Natural Gas) - A unit of volume equal to 1 cubic foot at a pressure base of 14.73 pounds standard per square inch absolute and a temperature base of 60 degrees Fahrenheit. Cube Law - In reference to wind energy, for any given instant, the power available in the wind is proportional to the cube of the wind velocity; when wind speed doubles, the power availability increases eight times. Current (Electrical) - The flow of electrical energy (electricity) in a conductor, measured in amperes. Current Dollars - The value or purchasing power of a dollar that has not been reduced to a common basis of constant purchasing power, but instead reflects anticipated future inflation; when used in computations the assumed inflation rate must be stated.

Customer Charge - An amount to be paid for energy periodically by a customer without regard to demand or energy consumption. Customer Class - Categories of energy consumers, as defined by consumption or demand levels, patterns, and conditions, and generally included residential, commercial, industrial, agricultural. Cut-In-Speed - The lowest wind speed at which a wind turbine begins producing useable power. Cut-Out-Speed - The highest wind speed at which a wind turbine stops producing power. Cycle - In alternating current, the current goes from zero potential or voltage to a maximum in one direction, back to zero, and then to a maximum potential or voltage in the other direction. The number of complete cycles per second determines the current frequency; in the U.S. the standard for alternating current is 60 cycles. Cycling Losses - The loss of heat as the water circulates through a water heater tank and inlet and outlet pipes. Cyclone Burner - A furnace/combustion chamber in which finely ground fuel is blown in spirals in the combustion chamber to maximize combustion efficiency. Czochralski Process - A method of growing large size, high quality semiconductor crystal by slowly lifting a seed crystal from a molten bath of the material under careful cooling conditions.

Dam - A structure for impeding and controlling the flow of water in a water course, and which increases the water elevation to create the hydraulic head. The reservoir creates, in effect, stored energy. Damper - A movable plate used to control air flow; in a wood stove or fireplace, used to control the amount and direction of air going to the fire. Darrieus (Wind) Machine - A type of vertical-axis wind machine that has long, thin blades in the shape of loops connected to the top and bottom of the axle; often called an "eggbeater windmill." Daylighting - The use of direct, diffuse, or reflected sunlight to provide supplemental lighting for building interiors. Decentralized (Energy) System - Energy systems supply individual, or small-groups, of energy loads. Declination - The angular position of the sun at solar noon with respect to the plane of the equator. Declining Block Rate - An electricity supplier rate structure in which the per unit price of electricity decreases as the amount of energy increases. Normally only available to very large consumers. Decommissioning - The process of removing a power plant, apparatus, equipment, building, or facility from operation. Decomposition - The process of breaking down organic material; reduction of the net energy level and change in physical and chemical composition of organic material. De-energize(d) - To disconnect a transmission and/or distribution line; a power line that is not carrying a current; to open a circuit. Deep Discharge - Discharging a battery to 20 percent or less of its full charge capacity. Degree Day - A unit for measuring the extent that the outdoor daily average temperature (the mean of the maximum and minimum daily dry-bulb temperatures) falls below (in the case of heating, see Heating Degree Day), or falls above (in the case of cooling, see Cooling Degree Day) an assumed base temperature, normally taken as 65 degrees Fahrenheit, unless otherwise stated. One degree day is counted for

each degree below (for heating) or above (in the case of cooling) the base, for each calendar day on which the temperature goes below or above the base. Degree Hour - The product of 1 hour, and usually the number of degrees Fahrenheit the hourly mean temperature is above a base point (usually 65 degrees Fahrenheit); used in roughly estimating or measuring the cooling load in cases where processes heat, heat from building occupants, and humidity are relatively unimportant compared to the dry-bulb temperature. Dehumidifier - A device that cools air by removing moisture from it. Demand - The rate at which electricity is delivered to or by a system, part of a system, or piece of equipment expressed in kilowatts, kilovoltamperes, or other suitable unit, at a given instant or averaged over a specified period of time. Demand Charge - A charge for the maximum rate at which energy is used during peak hours of a billing period. That part of a utility service charged for on the basis of the possible demand as distinguished from the energy actually consumed. Demand(ed) Factor - The ratio of the maximum demand on an electricity generating and distribution system to the total connected load on the system; usually expressed as a percentage. Demand Power - see Peak Power Demand-Side Management (DSM) - The process of managing the consumption of energy, generally to optimize available and planned generation resources. Demand (Tankless) Water Heater - A type of water heater that has no storage tank thus eliminating storage tank standby losses. Cold water travels through a pipe into the unit, and either a gas burner or an electric element heats the water only when needed. Dendrite - A slender threadlike spike of pure crystalline material, such as silicon. Dendritic Web Technique - A method for making sheets of polycrystalline silicon in which silicon dendrites are slowly withdrawn

from a melt of silicon whereupon a web of silicon forms between the dendrites and solidifies as it rises from the melt and cools. Department of Agriculture (USDA) - A federal government agency involved in rural development, marketing and regulatory programs, food safety, research, education and economics, food, nutrition and consumer service, farm and foreign agricultural services, and natural resources and environment programs. Department of Energy (DOE) - A federal government agency created in 1977, that is entrusted to contribute to the welfare of the United States by providing technical information, and a scientific and educational foundation for technology, policy and institutional leadership to achieve efficiency in energy use, diversity in energy sources, a more productive and competitive economy, improved environmental quality, and a secure national defense. Dependable Capacity - The load-carrying ability of an electric power plant during a specific time interval and period when related to the characteristics of the load to be/being supplied; determined by capability, operating power factor, and the portion of the load the station is to supply. Derating - The production of energy by a system or appliance at a level less than its design or nominal capacity. Deregulation - The process of changing regulatory policies and laws to increase competition among suppliers of commodities and service. The process of deregulating the electric power industry was initiated by the Energy Policy Act of 1992. (See also Restructuring) Desiccant - A material used to desiccate (dry) or dehumidify air. Dessicant Cooling - To condition/cool air by dessication. Desiccation - The process of removing moisture; involves evaporation. Design Cooling Load - The amount of conditioned air to be supplied by a cooling system; usually the maximum amount to be delivered based on a specified number of cooling degree days or design temperature.

Design Heating Load - The amount of heated air, or heating capacity, to be supplied by a heating system; usually the maximum amount to be delivered based on a specified number of heating degree days or design outside temperature. Design Life - Period of time a system or appliance (or component of) is expected to function at its nominal or design capacity without major repair. Design Temperature - The temperature that a system is designed to maintain (inside) or operate against (outside) under the most extreme conditions. Design Tip Speed Ratio - For a wind turbine, the ratio of the speed of the tip of a turbine blade for which the power coefficient is at maximum. Design Voltage - The nominal voltage for which a conductor or electrical appliance is designed; the reference voltage for identification and not necessarily the precise voltage at which it operates. Desuperheater - An energy saving device in a heat pump that, during the cooling cycle, recycles some of the waste heat from the house to heat domestic water. Dewpoint - The temperature to which air must be cooled, at constant pressure and water vapor content, in order for saturation or condensation to occur; the temperature at which the saturation pressure is the same as the existing vapor pressure; also called saturation point. Difference of Potential - The difference in electrical pressure (voltage) between any two points in an electrical system or between any point in an electrical system and the earth. Differential Thermostat - A type of automatic thermostat (used on solar heating systems) that responds to temperature differences (between collectors and the storage components) so as to regulate the functioning of appliances (to switch transfer fluid pumps on and off). Diffuse Solar Radiation - Sunlight scattered by atmospheric particles and gases so that it arrives at the earth's surface from all directions and can not be focused.

Diffusion - The movement of individual molecules through a material; permeation of water vapor through a material. Diffusion Length - The mean distance a free electron or hole moves before recombining with another hole or electron. Digester (Anaerobic) - A device in which organic material is biochemically decomposed (digested) by anaerobic bacteria to treat the material and/or to produce biogas. Dimmer - A light control device that allows light levels to be manually adjusted. A dimmer can save energy by reducing the amount of power delivered to the light while consuming very little themselves. Dip Tube - A tube inside a domestic water heater that distributes the cold water from the cold water supply line into the lower area of the water heater where heating occurs. Diode - An electronic device that allows current to flow in one direction only. Direct Access - The ability of an electric power consumer to purchase electricity from a supplier of their choice without being physically inhibited by the owner of the electric distribution and transmission system to which the consumer is connected to. (See also Open Access.) Direct Beam Radiation - Solar radiation that arrives in a straight line from the sun. Direct Current - A type of electricity transmission and distribution by which electricity flows in one direction through the conductor; usually relatively low voltage and high current; typically abbreviated as dc. Direct-Gain - The process by which sunlight directly enters a building through the windows and is absorbed and stored in massive floors or walls. Direct Vent Heater - A type of combustion heating system in which combustion air is drawn directly from outside and the products of combustion are vented directly outside. These features are beneficial in tight, energy-efficient homes because they will not depressurize a home and cause air infiltration, and backdrafting of other combustion appliances.

Direct Water Heater - A type of water heater in which heated water is stored within the tank. Hot water is released from the top of the tank when a hot water faucet is turned. This water is replaced with cold water that flows into the tank and down to just above the bottom plate under which are the burners. Discounting - A method of financial and economic analysis used to determine present and future values of investments or expenses. Discount Rate - The interest rate at which the Federal Reserve System stands ready to lend reserves to commercial banks. The rate is proposed by the 12 Federal Reserve banks and determined with the approval of the Board of Governors. Dispatching - To schedule and control the generation and delivery of electric power. Dispachability - The ability to dispatch power. Displacement Power - A source of power (electricity) that can displace power from another source so that source's power can be transmitted to more distant loads. Distributed Generation - A popular term for localized or on-site power generation. Distribution - The process of distributing electricity; usually defines that portion of an electrical utility's power lines between a utility's power pole and transformer and a customer's point of connection/meter. Distribution Feeder (see Feeder) Distribution Line - One or more circuits of a distribution system on the same line or poles or supporting structures' usually operating at a lower voltage relative to the transmission line. Distribution System - That portion of an electricity supply system used to deliver electricity from points on the transmission system to consumers. District Heating - A heating system in which steam or hot water for space heating or hot water is piped from a central boiler plant or electric power/heating plant to a cluster of buildings.

Diversity Factor - The ratio of the sum of the noncoincidental maximum demands of two or more loads to their coincidental maximum demands for the same period. DOE-2.1 - A computer software program that simulates energy consumption of commercial buildings; used for design and auditing purposes. Dome (Geodesic) - An architectural design invented by Buckminster Fuller with a regular polygonal structure based on radial symmetry. Domestic Hot Water - Water heated for residential washing, bathing, etc. Donor - In a solar photovoltaic device, an n-type dopant, such as phosphorus, that puts an additional electron into an energy level very near the conduction band; this electron is easily exited into the conduction band where it increases the electrical conductivity over than of an undoped semiconductor. Dopant - A chemical element (impurity) added in small amounts to an otherwise pure semiconductor material to modify the electrical properties of the material. An n-dopant introduces more electrons. A p-dopant creates electron vacancies (holes). Doping - The addition of dopants to a semiconductor. Double-Pane or Glazed Window - A type of window having two layers (panes or glazing) of glass separated by an air space. Each layer of glass and surrounding air space reradiates and traps some of the heat that passes through thereby increasing the windows resistance to heat loss (R-value). Double Wall Heat Exchanger - A heat exchanger in a solar water heating system that has two distinct walls between the heat transfer fluid and the domestic water, to ensure that there is no mixing of the two. Downwind Wind Turbine - A horizontal axis wind turbine in which the rotor is downwind of the tower. Draft - A column of burning combustion gases that are so hot and strong that the heat is lost up the chimney before it can be transferred to the house. A draft brings air to the fire to help keep it burning.

Draft Diverter - A door-like device located at the mouth of a fireplace chimney flue for controlling the direction and flow of the draft in the fireplace as well as the amount of oxygen that the fire receives. Draft Hood - A device built into or installed above a combustion appliance to assure the escape of combustion byproducts, to prevent backdrafting of the appliance, or to neutralize the effects of the stack action of the chimney or vent on the operation of the appliance. Drainback (Solar) Systems - A closed-loop solar heating system in which the heat transfer fluid in the collector loop drains into a tank or reservoir whenever the booster pump stops to protect the collector loop from freezing. Draindown (Solar) Systems - An open-loop solar heating system in which the heat transfer fluid from the collector loop and the piping drain into a drain whenever freezing conditions occur. Dry Bulb Temperature - The temperature of the air as measured by a standard thermometer. Dry Steam Geothermal Plants - Conventional turbine generators are used with the dry steam resources. The steam is used directly, eliminating the need for boilers and boiler fuel that characterizes other steam-power-generating technologies. This technology is limited because dry-steam hydrothermal resources are extremely rare. The Geysers, in California, is the nation's only dry steam field. Dual Duct System - An air conditioning system that has two ducts, one is heated and the other is cooled, so that air of the correct temperature is provided by mixing varying amounts of air from each duct. Dual Fuel (or Flex Fuel) Vehicle - A vehicle with an engine capable of operating on two different types of fuels. Duct(s) - The round or rectangular tube(s), generally constructed of sheet metal, fiberglass board, or a flexible plastic-and-wire composite, located within a wall, floor, and ceiling that distributes heated or cooled air in buildings. Duct Fan - An axail flow fan mounted in a section of duct to move conditioned air.

Duty Cycle - The duration and periodicity of the operation of a device. Dynamo - A machine for converting mechanical energy into electrical energy by magneto-electric induction; may be used as a motor. Dynamic Head - The pressure equivalent of the velocity of a fluid. Dynamometer - An apparatus for measuring force or power, especially the power developed by a motor. Dyne - The absolute centimeter-gram-second unit of force; that force that will impart to a free mass of one gram an acceleration of one centimeter per second per second.

Earth Berm - A mound of dirt next to exterior walls to provide wind protection and insulation. Earth Cooling Tube - A long, underground metal or plastic pipe through which air is drawn. As air travels through the pipe it gives up some of its heat to the soil, and enters the house as cooler air. Earth-Coupled Ground Source (Geothermal) Heat Pump - A type of heat pump that uses sealed horizontal or vertical pipes, buried in the ground, as heat exchangers through which a fluid is circulated to transfer heat. Earth Sheltered Houses - Houses that have earth berms around exterior walls. Earth-Ship - A registered trademark name for houses built with tires, aluminum cans, and earth. Easement - An incorporated right, liberty, privilege, or use of another entity's property, distinct from ownership, without profit or compensation; a right-of-way. Eccentric - A device for converting continuous circular motion into reciprocating rectilinear motion. Economizer - A heat exchanger for recovering heat from flue gases for heating water or air. Edge-Defined Film-Fed Growth (EFG) - A method for making sheets of polycrystalline silicon (for solar photovlotaic devices) in which molten silicon is drawn upward by capillary action through a mold. Efficacy - The amount of energy service or useful energy delivered per unit of energy input. Often used in reference to lighting systems, where the visible light output of a luminary is relative to power input; expressed in lumens per Watt; the higher the efficacy value, the higher the energy efficiency. Effective Capacity - The maximum load that a device is capable of carrying. Efficiency - Under the First Law of Thermodynamics, efficiency is the ratio of work or energy output to work or energy input, and cannot

exceed 100 percent. Efficiency under the Second Law of Thermodynamics is determined by the ratio of the theoretical minimum energy that is required to accomplish a task relative to the energy actually consumed to accomplish the task. Generally, the measured efficiency of a device, as defined by the First Law, will be higher than that defined by the Second Law. Efficiency (Appliance) Ratings - A measure of the efficiency of an appliance's energy efficiency. Elasticity of Demand - The ratio of the percentage change in the quantity of a good or service demanded to the percentage change in the price. Electrical Energy - The energy of moving electrons. Electrical Charge - A condition that results from an imbalance between the number of protons and the number of electrons in a substance. Electrical System - All the conductors and electricity using devices that are connected to a source of electromotive force (or generator). Electrical System Energy Losses - A measure of the amount of energy lost during the generation, transmission, and distribution of electricity. Electric Circuit - The path followed by electrons from a generation source, through an electrical system, and returning to the source. Electric Energy - The amount of work accomplished by electrical power, usually measured in kilowatt-hours (kWh). One kWh is 1,000 Watts and is equal to 3,413 Btu. Electric Furnace - An air heater in which air is blown over electric resistance heating coils. Electricity Generation - The process of producing electricity by transforming other forms or sources of energy into electrical energy; measured in kilowatt-hours. Electric Rate - The unit price and quantity to which it applies as specified in a rate schedule or contract.

Electric Rate Schedule - A statement of the electric rate(s), terms, and conditions for electricity sale or supply. Electric System - The physically connected generation, transmission, and distribution facilities and components operated as a unit. Electric System Loss(es) - The total amount of electric energy loss in an electric system between the generation source and points of delivery. Electric Power Plant - A facility or piece of equipment that produces electricity. Electric Power Transmission - The transmission of electricity through power lines. Electric Resistance Heating - A type of heating system where heat, resulting when electric current flows through an "element" or conductor, such as Nichrome, which has a high resistance, is radiated to a room. Electric Utility - A corporation, person, agency, authority or other legal entity that owns and/or operates facilities for the generation, transmission, distribution or sale of electricity primarily for use by the public. Electric Utility Sector - Those privately or publicly owned establishments that generate, transmit, distribute, or sell electricity. Electric Vehicles - A battery-powered electrically driven vehicle. Electrochemical Cell - A device containing two conducting electrodes, one positive and the other negative, made of dissimilar materials (usually metals) that are immersed in a chemical solution (electrolyte) that transmits positive ions from the negative to the positive electrode and thus forms an electrical charge. One or more cells constitute a battery. Electrode - A conductor that is brought in conducting contact with a ground. Electrodeposition - Electrolytic process in which a metal is deposited at the cathode from a solution of its ions.

Electrolysis - A chemical change in a substance that results from the passage of an electric current through an electrolyte. The production of commercial hydrogen by separating the elements of water, hydrogen, and oxygen, by charging the water with an electrical current. Electrolyte - A nonmetallic (liquid or solid) conductor that carries current by the movement of ions (instead of electrons) with the liberation of matter at the electrodes of an electrochemical cell. Electromagnetic Energy - Energy generated from an electromagnetic field produced by an electric current flowing through a superconducting wire kept at a specific low temperature. Electromagnetic Field (EMF) - The electrical and magnetic fields created by the presence or flow of electricity in an electrical conductor or electricity consuming appliance or motor. Electromotive Force - The amount of energy derived from an electrical source per unit quantity of electricity passing through the source. Electron - An elementary particle of an atom with a negative electrical charge and a mass of 1/1837 of a proton; electrons surround the positively charged nucleus of an atom and determine the chemical properties of an atom. Electronic Ballast - A device that uses electronic components to regulate the voltage of fluorescent lamps. Electron Volt - The amount of kinetic energy gained by an electron when accelerated through an electric potential difference of 1 Volt; equivalent to 1.603 x 10^-12; a unit of energy or work; abbreviated as eV. Electrostatic Precipitator - A device used to remove particulate matter from the waste gasses of a combustion power plant. Ellipsoidal Reflector Lamp - A lamp where the light beam is focused 2 inches ahead of the lamp reducing the amount of light trapped in the fixture. Emission(s) - A substance(s) or pollutant emitted as a result of a process.

Emission Factor - A measure of the average amount of a specified pollutant or material emitted for a specific type of fuel or process. Emissivity - The ratio of the radiant energy (heat) leaving (being emitted by) a surface to that of a black body at the same temperature and with the same area; expressed as a number between 0 and 1. Enclosure - The housing around a motor that supports the active parts and protects them. They come in different varieties (open, protected) depending on the degree of protection required. Endothermic - A heat absorbing reaction or a reaction that requires heat. End Use - The purpose for which useful energy or work is consumed. Energize(d) - To send electricity through a electricity transmission and distribution network; a conductor or power line that is carrying current. Energy - The capability of doing work; different forms of energy can be converted to other forms, but the total amount of energy remains the same. Energy Audit - A survey that shows how much energy you use in your house or apartment. It will help you find ways to use less energy. Energy Charge - That part of an electricity bill that is based on the amount of electrical energy consumed or supplied. Energy Contribution Potential - Recombination occurring in the emitter region of a photovoltaic cell. Energy Crops - Crops grown specifically for their fuel value. These include food crops such as corn and sugarcane, and nonfood crops such as poplar trees and switchgrass. Currently, two energy crops are under development: short-rotation woody crops, which are fastgrowing hardwood trees harvested in 5 to 8 years; and herbaceous energy crops, such as perennial grasses, which are harvested annually after taking 2 to 3 years to reach full productivity. Energy Efficient Mortgages - A type of home mortgage that takes into account the energy savings of a home that has cost-effective energy saving improvements that will reduce energy costs thereby

allowing the homeowner to more income to the mortgage payment. A borrower can qualify for a larger loan amount than otherwise would be possible. Energy Efficiency Ratio (EER) - The measure of the instantaneous energy efficiency of room air conditioners; the cooling capacity in Btu/hr divided by the watts of power consumed at a specific outdoor temperature (usually 95 degrees Fahrenheit). Energy Density - The ratio of available energy per pound; usually used to compare storage batteries. Energy Factor (EF) - The measure of overall efficiency for a variety of appliances. For water heaters, the energy factor is based on three factors: 1) the recovery efficiency, or how efficiently the heat from the energy source is transferred to the water; 2) standby losses, or the percentage of heat lost per hour from the stored water compared to the content of the water: and 3) cycling losses. For dishwashers, the energy factor is defined as the number of cycles per kWh of input power. For clothes washers, the energy factor is defined as the cubic foot capacity per kWh of input power per cycle. For clothes dryers, the energy factor is defined as the number of pounds of clothes dried per kWh of power consumed. Energy End-Use Sectors - Major energy consuming sectors of the economy. The Commercial Sector includes commercial buildings and private companies. The Industrial Sector includes manufacturers and processors. The Residential Sector includes private homes. The Transportation Sector includes automobiles, trucks, rail, ships, and aircraft. Energy Guide Labels - The labels placed on appliances to enable consumers to compare appliance energy efficiency and energy consumption under specified test conditions as required by the Federal Trade Commission. Energy Intensity - The relative extent that energy is required for a process. Energy Policy Act of 1992 (EPAct) - A comprehensive legislative package that mandates and encourages energy efficiency standards, alternative fuel use, and the development of renewable energy technologies. Public Law 102-486, October 24th, 1992. Also authorized the Federal Energy Regulatory Commission (FERC) to order the owners

of electric power transmission lines to transmit or "wheel" power for power generators including electric utilities, federal power marketing authorities, and exempt wholesale generators. Energy Security Act of 1980 - Legislation authorizing a U.S. biomass and alcohol fuel program, and that authorized loan guarantees and price guarantees and purchase agreements for alcohol fuel production. Energy Service Company (ESCo) - A company that specializes in undertaking energy efficiency measures under a contractual arrangement whereby the ESCo shares the value of energy savings with their customer. Energy Storage - The process of storing, or converting energy from one form to another, for later use; storage devices and systems include batteries, conventional and pumped storage hydroelectric, flywheels, compressed gas, and thermal mass. Enthalpy - A thermodynamic property of a substance, defined as the sum of its internal energy plus the pressure of the substance times its volume, divided by the mechanical equivalent of heat. The total heat content of air; the sum of the enthalpies of dry air and water vapor, per unit weight of dry air; measured in Btu per pound (or calories per kilogram). Entrained Bed Gasifier - A gasifier in which the feedstock (fuel) is suspended by the movement of gas to move it through the gasifier. Entropy - A measure of the unavailable or unusable energy in a system; energy that cannot be converted to another form. Environment - All the natural and living things around us. The earth, air, weather, plants, and animals all make up our environment. Epitaxial Growth - In reference to solar photovoltaic devices, the growth of one crystal on the surface of another crystal. The growth of the deposited crystal is oriented by the lattice structure of the original crystal. Equinox - The two times of the year when the sun crosses the equator and night and day are of equal length; usually occurs on March 21st (spring equinox) and September 23 (fall equinox).

Erg - A unit of work done by the force of one dyne acting through a distance of one centimeter. Ethanol - Ethyl alcohol (C2H5OH) - A colorless liquid that is the product of fermentation used in alcoholic beverages, industrial processes, and as a fuel additive. Also known as grain alcohol. Ethyl Tertiary Butyl Ether (ETBE) - A chemical compound produced in a reaction between ethanol and isobutylene (a petroleum-derived by-product of the refining process). ETBE has characteristics superior to other ethers: low volatility, low water solubility, high octane value, and a large reduction in carbon monoxide and hydrocarbon emissions. Eutectic - A mixture of substances that has a melting point lower than that of any mixture of the same substances in other proportions. Eutectic Salts - Salt mixtures with potential applications as solar thermal energy storage materials. Evacuated Tube Collector - A solar collector in which the absorber is contained in a sealed glass tube, thereby providing for relatively high temperature heat gain. Evaporation - The conversion of a liquid to a vapor (gas), usually by means of heat. Evaporative Cooling - The physical process by which a liquid or solid is transformed into the gaseous state. For this process a mechanical device uses the outside air's heat to evaporate water that is held by pads inside the cooler. The heat is drawn out of the air through this process and the cooled air is blown into the home by the cooler's fan. Evaporator Coil - The inner coil in a heat pump that, during the cooling mode, absorbs heat from the inside air and boils the liquid refrigerant to a vapor, which cools the house. Excitation - The power required to energize the magnetic field of a generator. Exempt Wholesale Generator - An unregulated subsidiary of an electric utility that is allowed to generate and sell wholesale power as an independent energy producer, and is exempt from the Public Utility Holding Company Act of 1935.

Exothermic - A reaction or process that produces heat; a combustion reaction. Expanded Polystyrene - A type of insulation that is molded or expanded to produce coarse, closed cells containing air. The rigid cellular structure provides thermal and acoustical insulation, strength with low weight, and coverage with few heat loss paths. Often used to insulate the interior of masonry basement walls. Expansion Tank - A tank used in a closed-loop solar heating system that provides space for the expansion of the heat transfer fluid in the pressurized collector loop. Expansion Valve - The device that reduces the pressure of liquid refrigerant thereby cooling it before it enters the evaporator coil in a heat pump. External Combustion Engine - An engine in which fuel is burned (or heat is applied) to the outside of a cylinder; a Stirling engine. Externality - The environmental, social, and economic impacts of producing a good or service that are not directly reflected in the market price of the good or service. Extruded Polystyrene - A type of insulation material with fine, closed cells, containing a mixture of air and refrigerant gas. This insulation has a high R-value, good moisture resistance, and high structural strength compared to other rigid insulation materials.

Fan - A device that moves and/or circulates air and provides ventilation for a room or a building. Fan Coil - A heat exchanger coil in which a fluid such as water is circulated and a fan blows air over the coil to distribute heat or cool air to the different rooms. Fan Velocity Pressure - The pressure corresponding to the outlet velocity of a fan; the kinetic energy per unit volume of flowing air. Farad - A unit of electrical capacitance; the capacitance of a capacitor between the plates of which there appears a difference of 1 Volt when it is charged by one coulomb of electricity. Feather - In a wind energy conversion system, to pitch the turbine blades so as to reduce their lift capacity as a method of shutting down the turbine during high wind speeds. Federal Energy Management Program (FEMP) - A program of the U.S. Department of Energy (DOE) that implements energy legislation and presidential directives. FEMP provides project financing, technical guidance and assistance, coordination and reporting, and new initiatives for the federal government. It also helps federal agencies identify the best technologies and technology demonstrations for their use. Federal Energy Regulatory Commission (FERC) - This is an independent regulatory agency within the U.S. DOE that has jurisdiction over interstate electricity sales, wholesale electric rates, natural gas pricing, oil pipeline rates, and gas pipeline certification. It also licenses and inspects private, municipal, and state hydroelectric projects and oversees related environmental matters. Federal Power Marketing Administrations (PMA) - These are separate and distinct organizational agencies within the U.S. DOE that market power at federal multipurpose water projects at lowest possible rates to consumers consistent with sound business principles. There are five PMA's: Alaska Power Administration, Bonneville Power Administration, Southeastern Power Administration, Southwestern Power Administration, Western Area Power Administration. Feeder - A power line for supplying electricity within a specified area.

Feedstock - A raw material that can be converted to one or more products. Fenestration - The arrangement, proportion, and design of windows in a building. Fermentation - The decomposition of organic material to alcohol, methane, etc., by organisms, such as yeast or bacteria, usually in the absence of oxygen. Fiberglass Insulation - A type of insulation, composed of small diameter pink, yellow, or white glass fibers, formed into blankets or batts, or used in loose-fill and blown-in applications. Filament - A coil of tungsten wire suspended in a vacuum or inert gas-filled bulb. When heated by electricity the tungsten "filament" glows. Fill Factor - The ratio of a photovoltaic cell's actual power to its power if both current and voltage were at their maxima. A key characteristic in evaluating cell performance. Filter (air) - A device that removes contaminants, by mechanical filtration, from the fresh air stream before the air enters the living space. Filters can be installed as part of a heating/cooling system through which air flows for the purpose of removing particulates before or after the air enters the mechanical components. Fin - A thin sheet of material (metal) of a heat exchanger that conducts heat to a fluid. Finish - Both a noun and a verb to describe the exterior surface of building elements (walls, floors, ceilings, etc.) and furniture, and the process of applying it. Fire Classification - Classifications of fires developed by the National Fire Protection Association. Fireplace - A wood or gas burning appliance that is primarily used to provide ambiance to a room. Conventional, masonry fireplaces without energy saving features, often take more heat from a space than they put into it.

Fireplace Insert - A wood or gas burning heating appliance that fits into the opening or protrudes on to the hearth of a conventional fireplace. Fire-Rating - The ability of a building construction assembly (partition, wall, floor, etc.) to resist the passage of fire. The rating is expressed in hours. Firewall - A wall to prevent the spread of fire; usually made of noncombustible material. Firing Rate - The amount of BTU's/hour or kW's produced by a heating system from the burning of a fuel. First Law of Thermodynamics - States that energy cannot be created or destroyed, but only changed from one form to another. First Law efficiency measures the fraction of energy supplied to a device or process that it delivers in its output. Also called the law of conservation of energy. Fiscal Year - The U.S. Government's 12-month financial year, from October to September, of the following calender year; e.g.: FY 1998 extends from Oct. 1, 1997 to Sept. 30, 1988. Flame Spread Classification - A measure of the surface burning characteristics of a material. Flame Spread Rating - A measure of the relative flame spread, and smoke development, from a material being tested. The flame spread rating is a single number comparing the flame spread of a material with red oak, arbitrarily given the number 100 and asbestos cement board with a flame spread of 0. Building codes require a maximum flame spread of 25 for insulation installed in exposed locations. Flash-Steam Geothermal Plants - When the temperature of the hydrothermal liquids is over 350 F (177 C), flash-steam technology is generally employed. In these systems, most of the liquid is flashed to steam. The steam is separated from the remaining liquid and used to drive a turbine generator. While the water is returned to the geothermal reservoir, the economics of most hydrothermal flash plants are improved by using a dual-flash cycle, which separates the steam at two different pressures. The dual-flash cycle produces 20% to 30% more power than a single-flash system at the same fluid flow.

Flashing - Metal, usually galvanized sheet metal, used to provide protection against infiltration of precipitation into a roof or exterior wall; usually placed around roof penetrations such as chimneys. Flashpoint - The minimum temperature at which sufficient vapor is released by a liquid or solid (fuel) to form a flammable vapor-air mixture at atmospheric pressure. Flat-Black Paint - Nonglossy paint with a relatively high absorptance. Flat-Plate Solar Thermal/Heating Collectors - Large, flat boxes with glass covers and dark-colored metal plates inside that absorb and transfer solar energy to a heat transfer fluid. Flat-Plate Solar Photovoltaic Module - An arrangement of photovoltaic cells or material mounted on a rigid flat surface with the cells exposed freely to incoming sunlight. Flat Roof - A slightly sloped roof, usually with a tar and gravel cover. Most commercial buildings use this kind of roof. Float-Zone Process - In reference to solar photovoltaic cell manufacure, a method of growing a large-size, high-quality crystal whereby coils heat a polycrystalline ingot placed atop a single-crystal seed. As the coils are slowly raised the molten interface beneath the coils becomes a single crystal. Floor - The upward facing structure of a building. Floorspace - The interior area of a building, calculated in square feet or meters. Flow Condition - In reference to solar thermal collectors, the condition where the heat transfer fluid is flowing through the collector loop under normal operating conditions. Flow Restrictor - A water and energy conserving device that limits the amount of water that a faucet or showerhead can deliver. Flue - The structure (in a residential heating appliance, industrial furnace, or power plant) into which combustion gases flow and are contained until they are emitted to the atmosphere.

Flue Gas - The gas resulting from the combustion of a fuel that is emitted to the flue. Fluffing - The practice of installing blow-in, loose-fill insulation at a lower density than is recommended to meet a specified R-Value. Fluidized Bed Combustion (FBC) - A type of furnace or reactor in which fuel particles are combusted while suspended in a stream of hot gas. Fluorescent Light - The conversion of electric power to visible light by using an electric charge to excite gaseous atoms in a glass tube. These atoms emit ultraviolet radiation that is absorbed by a phosphor coating on the walls of the lamp tube. The phosphor coating produces visible light. Fly Ash - The fine particulate matter entrained in the flue gases of a combustion power plant. Flywheel Effect - The damping of interior temperature fluctuations by massive construction. Foam (Insulation) - A high R-value insulation product usually made from urethane that can be injected into wall cavities, or sprayed onto roofs or floors, where it expands and sets quickly. Foam Board - A plastic foam insulation product, pressed or extruded into board-like forms, used as sheathing and insulation for interior basement or crawl space walls or beneath a basement slab; can also be used for exterior applications inside or outside foundations, crawlspaces, and slab-on-grade foundation walls. Foam Core Panels - A type of structural, insulated product with foam insulation contained between two facings of drywall, or structural wood composition boards such as plywood, waferboard, and oriented strand board. Foot Candle - A unit of illuminance; equal to one lumen per square foot. Foot Pound - The amount of work done in raising one pound one foot.

Force - The push or pull that alters the motion of a moving body or moves a stationairy body; the unit of force is the dyne or poundal; force is equal to mass time velocity divided by time. Forced Air System or Furnace - A type of heating system in which heated air is blown by a fan through air channels or ducts to rooms. Forced Ventilation - A type of building ventilation system that uses fans or blowers to provide fresh air to rooms when the forces of air pressure and gravity are not enough to circulate air through a building. Formaldehyde - A chemical used as a preservative and in bonding agents. It is found in household products such as plywood, furniture, carpets, and some types of foam insulation. It is also a by-product of combustion and is a strong-smelling, colorless gas that is an eye irritant and can cause sneezing, coughing, and other health problems. Fossil Fuels - Fuels formed in the ground from the remains of dead plants and animals. It takes millions of years to form fossil fuels. Oil, natural gas, and coal are fossil fuels. Foundation - The supportive structure of a building. Fractional Horse Power Motor - An electric motor rated at less than one horse power (hp). Frame (Window) - The outer casing of a window that sits in a designated opening of a structure and holds the window panes in place. Framing - The structural materials and elements used to construct a wall. Francis Turbine - A type of hydropower turbine that contains a runner that has water passages through it formed by curved vanes or blades. As the water passes through the runner and over the curved surfaces, it causes rotation of the runner. The rotational motion is transmitted by a shaft to a generator. Frequency - The number of cycles through which an alternating current passes per second; in the U.S. the standard for electricity generation is 60 cycles per second (60 Hertz).

Freon - A registered trademark for a cholorflourocarbon (CFC) gas that is highly stable and that has been historically used as a refrigerant. Fresnel Lens - An optical device for concentrating light that is made of concentric rings that are faced at different angles so that light falling on any ring is focused to the same point. Friction Head - The energy lost from the movement of a fluid in a conduit (pipe) due to the disturbances created by the contact of the moving fluid with the surfaces of the conduit, or the additional pressure that a pump must provide to overcome the resistance to fluid flow created by or in a conduit. Fuel - Any material that can be burned to make energy. Fuel Cell - An electrochemical device that converts chemical energy directly into electricity. Fuel Efficiency - The ratio of heat produced by a fuel for doing work to the available heat in the fuel. Fuel Grade Alcohol - Usually refers to ethanol to 160 to 200 proof. Fuel Oil - Any liquid petroleum product burned for the generation of heat in a furnace or firebox, or for the generation of power in an engine. Domestic (residential) heating fuels are classed as Nos. 1, 2, 3; Industrial fuels as Nos. 4, 5, and 6. Fuel Rate - The amount of fuel necessary to generate one kilowatthour of electricity. Full Sun - The amount of power density in sunlight received at the earth's surface at noon on a clear day (about 1,000 Watts/square meter). Fungi - Plant-like organisms with cells with distinct nuclei surrounded by nuclear membranes, incapable of photosynthesis. Fungi are decomposers of waste organisms and exist as yeast, mold, or mildew. Furling - The process of forcing, either manually or automatically, a wind turbine's blades out of the direction of the wind in order to stop the blades from turning.

Furnace (Residential) - A combustion heating appliance in which heat is captured from the burning of a fuel for distribution, comprised mainly of a combustion chamber and heat exchanger. Fuse - A safety device consisting of a short length of relatively fine wire, mounted in a holder or contained in a cartridge and connected as part of an electrical circuit. If the circuit source current exceeds a predetermined value, the fuse wire melts (i.e. the fuse 'blows') breaking the circuit and preventing damage to the circuit protected by the fuse.

Gallium Arsenide - A compound used to make certain types of solar photovoltaic cells. Gasification - The process in which a solid fuel is converted into a gas; also known as pyrolitic distillation or pyrolysis. Production of a clean fuel gas makes a wide variety of power options available. Gasifier - A device for converting a solid fuel to a gaseous fuel. Gasket/Seal - A seal used to prevent the leakage of fluids, and also maintain the pressure in an enclosure. Gasohol - A registered trademark of an agency of the state of Nebraska, for an automotive fuel containing a blend of 10 percent ethanol and 90 percent gasoline. Gasoline - A refined petroleum product suitable for use as a fuel in internal combustion engines. Gas Turbine - A type of turbine in which combusted, pressurized gas is directed against a series of blades connected to a shaft, which forces the shaft to turn to produce mechanical energy. Gauss - The unit of magnetic field intensity equal to 1 dyne per unit pole. Generator - A device for converting mechanical energy to electrical energy. Geopressurized Brines - These brines are hot (300 F to 400 F) (149 C to 204 C) pressurized waters that contain dissolved methane and lie at depths of 10,000 ft (3048 m) to more than 20,000 ft (6096 m) below the earth's surface. The best known geopressured reservoirs lie along the Texas and Louisiana Gulf Coast. At least three types of energy could be obtained: thermal energy from high-temperature fluids; hydraulic energy from the high pressure; and chemical energy from burning the dissolved methane gas. Geothermal Energy - Energy produced by the internal heat of the earth; geothermal heat sources include: hydrothermal convective systems; pressurized water reservoirs; hot dry rocks; manual gradients; and magma. Geothermal energy can be used directly for heating or to produce electric power.

Geothermal Heat Pump - A type of heat pump that uses the ground, ground water, or ponds as a heat source and heat sink, rather than outside air. Ground or water temperatures are more constant and are warmer in winter and cooler in summer than air temperatures. Geothermal heat pumps operate more efficiently than "conventional" or "air source" heat pumps. Geothermal Power Station - An electricity generating facility that uses geothermal energy. Gigawatt (GW) - A unit of power equal to 1 billion Watts; 1 million kilowatts, or 1,000 Megawatts. Gin Pole - A pole used to assist in raising a tower. Glare - The discomfort or interference with visual perception when viewing a bright object against a dark background. Glazing - A term used for the transparent or translucent material in a window. This material (i.e. glass, plastic films, coated glass) is used for admitting solar energy and light through windows. Glauber's Salt - A salt, sodium sulfate decahydrate, that melts at 90 degrees Fahrenheit; a component of eutetic salts that can be used for storing heat. Glazing - Transparent or translucent material (glass or plastic) used to admit light and/or to reduce heat loss; used for building windows, skylights, or greenhouses, or for covering the aperture of a solar collector. Global Insolation (or Solar Radiation) - The total diffuse and direct insolation on a horizontal surface, averaged over a specified period of time. Global Warming - A popular term used to describe the increase in average global temperatures due to the greenhouse effect. Governor - A device used to regulate motor speed, or, in a wind energy conversion system, to control the rotational speed of the rotor. Grain Alcohol - Ethanol.

Greenhouse Effect - A popular term used to describe the heating effect due to the trapping of long wave (length) radiation by greenhouse gases produced from natural and human sources. Greenhouse Gases - Those gases, such as water vapor, carbon dioxide, tropospheric ozone, methane, and low level ozone that are transparent to solar radiation, but opaque to long wave radiation, and which contribute to the greenhouse effect. Greenwood - Freshly cut, unseasoned, wood. Greenpower - A popular term for energy produced from renewable energy resources. Green Pricing and Marketing - To price and sell greenpower/electricity higher than that produced from fossil or nuclear power plants, supposedly because some buyers are willing to pay a premium for greenpower. Greywater - Waste water from a household source other than a toilet. This water can be used for landscape irrigation depending upon the source of the greywater. Grid - A commmon term refering to an electricity transmission and distribution system. Gross Calorific Value - The heat produced by combusting a specific quantity and volume of fuel in an oxygen-bomb colorimeter under specific conditions. Gross Generation - The total amount of electricity produced by a power plant. Ground - A device used to protect the user of any electrical system or appliance from shock. Ground Reflection - Solar radiation reflected from the ground onto a solar collector. Ground-Source Heat Pump (see geothermal systems)

Harmonic(s) - A sinusoidal quantity having a frequency that is an integral multiple of the frequency of a periodic quantity to which it is related. Head - A unit of pressure for a fluid, commonly used in water pumping and hydropower to express height a pump must lift water, or the distance water falls. Total head accounts for friction head losses, etc. Heat - A form of thermal energy resulting from combustion, chemical reaction, friction, or movement of electricity. As a thermodynamic condition, heat, at a constant pressure, is equal to internal or intrinsic energy plus pressure times volume. Heat Absorbing Window Glass - A type of window glass that contains special tints that cause the window to absorb as much as 45% of incoming solar energy, to reduce heat gain in an interior space. Part of the absorbed heat will continue to be passed through the window by conduction and reradiation. Heat Balance - Energy output from a system that equals energy input. Heat Content - The amount of heat in a quantity of matter at a specific temperature and pressure. Heat Engine - A device that produces mechanical energy directly from two heat reservoirs of different temperatures. A machine that converts thermal energy to mechanical energy, such as a steam engine or turbine. Heat Exchanger - A device used to transfer heat from a fluid (liquid or gas) to another fluid where the two fluids are physically separated. Heat Gain - The amount of heat introduced to a space from all heat producing sources, such as building occupants, lights, appliances, and from the environment, mainly solar energy. Heating Capacity (Also specific heat) - The quantity of heat necessary to raise the temperature of a specific mass of a substance by one degree. Heating Degree Day(s) (HDD) - The number of degrees per day that the daily average temperature (the mean of the maximum and minimum recorded temperatures) is below a base temperature,

usually 65 degrees Fahrenheit, unless otherwise specified; used to determine indoor space heating requirements and heating system sizing. Total HDD is the cumulative total for the year/heating season. The higher the HDD for a location, the colder the daily average temperature(s). Heating Fuels - Any gaseous, liquid, or solid fuel used for indoor space heating. Heating Fuel Units - Standardized weights or volumes for heating fuels. Heating Load - The rate of heat flow required to maintain a specific indoor temperature; usually measured in Btu per hour. Heating Season - The coldest months of the year; months where average daily temperatures fall below 65 degrees Fahrenheit creating demand for indoor space heating. Heating Seasonal Performance Factor (HSPF) - The measure of seasonal or annual efficiency of a heat pump operating in the heating mode. It takes into account the variations in temperature that can occur within a season and is the average number of Btu of heat delivered for every watt-hour of electricity used by the heat pump over a heating season. Heating Value - The amount of heat produced from the complete combustion of a unit of fuel. The higher (or gross) heating value is that when all products of combustion are cooled to the pre-combustion temperature, water vapor formed during combustion is condensed, and necessary corrections have been made. Lower (or net) heating value is obtained by subtracting from the gross heating value the latent heat of vaporization of the water vapor formed by the combustion of the hydrogen in the fuel. Heating, Ventilation, and Air-Conditioning (HVAC) System - All the components of the appliance used to condition interior air of a building. Heat Loss - The heat that flows from the building interior, through the building envelope to the outside environment. Heat Pipe - A device that transfers heat by the continuous evaporation and condensation of an internal fluid.

Heat Pump - An electricity powered device that extracts available heat from one area (the heat source) and transfers it to another (the heat sink) to either heat or cool an interior space or to extract heat energy from a fluid. Heat Pump Water Heaters - A water heater that uses electricity to move heat from one place to another instead of generating heat directly. Heat Rate - The ratio of fuel energy input as heat per unit of net work output; a measure of a power plant thermal efficiency, generally expressed as Btu per net kilowatt-hour. Heat Recovery Ventilator - A device that captures the heat from the exhaust air from a building and transfers it to the supply/fresh fresh air entering the building to preheat the air and increase overall heating efficiency. Heat Register - The grilled opening into a room by which the amount of warm air from a furnace can be directed or controlled; may include a damper. Heat Sink - A structure or media that absorbs heat. Heat Source - A structure or media from which heat can be absorbed or extracted. Heat Storage - A device or media that absorbs heat for storage for later use. Heat Storage Capacity - The amount of heat that a material can absorb and store. Heat Transfer - The flow of heat from one area to another by conduction, convection, and/or radiation. Heat flows naturally from a warmer to a cooler material or space. Heat Transfer Fluid - A gas or liquid used to move heat energy from one place to another; a refrigerant. Heat Transmission Coefficient - Any coefficient used to calculate heat transmission by conduction, convection, or radiation through materials or structures.

Heliochemical Process - The utilization of solar energy through photosynthesis. Heliodon - A device used to simulate the angle of the sun for assessing shading potentials of building structures or landscape features. Heliostat - A device that tracks the movement of the sun; used to orient solar concentrating systems. Heliothermal - Any process that uses solar radiation to produce useful heat. Heliothermic - Site planning that accounts for natural solar heating and cooling processes and their relationship to building shape, orientation, and siting. Heliothermometer - An instrument for measuring solar radiation. Heliotropic - Any device (or plant) that follows the sun's apparent movement across the sky. Hemispherical Bowl Technology - A solar energy concentrating technology that uses a linear receiver that tracks the focal area of a reflector or array of reflectors. Hertz - A measure of the number of cycles or wavelengths of electrical energy per second; U.S. electricity supply has a standard frequency of 60 hertz. Heterojunction - A region of electrical contact between two different materials. Higher Heating Value (HHV)- The maximum heating value of a fuel sample, which includes the calorific value of the fuel (bone dry) and the latent heat of vaporization of the water in the fuel. (See moisture content and net (lower) heating value, below.) High-Intensity Discharge Lamp - A lamp that consists of a sealed arc tube inside a glass envelope, or outer jacket. The inner arc tube is filled with elements that emit light when ionized by electric current. A ballast is required to provide the proper starting voltage and to regulate current during operation.

High-Pressure Sodium Lamp - A type of High-Intensity Discharge (HID) lamp that uses sodium under high pressure as the primary lightproducing element. These high efficiency lights produce a golden white color and are used for interior industrial applications, such as in warehouses and manufacturing, and for security, street, and area lighting. Hole - The vacancy where an electron would normally exist in a solid; behaves like a positively charged particle. Home Energy Rating Systems (HERS) - A nationally recognized energy rating program that gives builders, mortgage lenders, secondary lending markets, homeowners, sellers, and buyers a precise evaluation of energy losing deficiency's in homes. Builders can use this system to gauge the energy quality in their home and also to have a star rating on their home to compare to other similarly built homes. Homojunction - The region between an n-layer and a p-layer in a single material, photovoltaic cell. Horizontal-Axis Wind Turbines - Turbines in which the axis of the rotor's rotation is parallel to the wind stream and the ground. Horsepower (Hp) - A unit of rate of operation. Electrical Hp: a measure of time rate of mechanical energy output; usually applied to electric motors as the maximum output; 1 electrical Hp is equal to 0.746 kilowatts or 2,545 Btu per hour. Shaft Hp: a measure of the actual mechanical energy per unit time delivered to a turning shaft; 1 shaft Hp is equal to 1 electrical Hp or 550 foot pounds per second. Boiler Hp: a measure to the maximum rate to heat output of a steam generator; 1 boiler Hp is equal to 33,480 Btu per hour steam output. Horsepower Hour (Hph) - One horsepower provided over one hour; equal to 0.745 kilowatt-hour or 2,545 Btu. Hot Air Furnace - A heating unit where heat is distributed by means of convection or fans. Hot Dry Rock - A geothermal energy resource that consists of high temperature rocks above 300 F (150 C) that may be fractured and have little or no water. To extract the heat, the rock must first be fractured, then water is injected into the rock and pumped out to extract the heat. In the western United States, as much as 95,000 square miles (246,050 square km) have hot dry rock potential.

Hot Water Heating Systems (see hydronic) Hub Height - The height above the ground that a horizontal axis wind turbine's hub is located. Humidifier - A device used to maintain a specified humidity in a conditioned space. Humidity - A measure of the moisture content of air; may be expressed as absolute, mixing ratio, saturation deficit, relative, or specific. Hybrid Renewable Energy System - A renewable energy system that includes two different types of renewable energy technologies that produce the same type of energy; for e.g., a wind turbine and a solar photovoltaic array combined to meet a power demand. Hydroelectric Power Plant - A power plant that produces electricity by the force of water falling through a hydro turbine that spins a generator. Hydrogen - A chemical element that can be used as a fuel since it has a very high energy content. Hydrogenated Amorphous Silicon - Amorphous silicon with a small amount of incorporated hydrogen. The hydrogen neutralizes dangling bonds in the amorphous silicon, allowing charge carriers to flow more freely. Hydronic Heating Systems - A type of heating system where water is heated in a boiler and either moves by natural convection or is pumped to heat exchangers or radiators in rooms; radiant floor systems have a grid of tubing laid out in the floor for distributing heat. The temperature in each room is controlled by regulating the flow of hot water through the radiators or tubing. Hydrothermal fluids - These fluids can be either water or steam trapped in fractured or porous rocks; they are found from several hundred feet to several miles below the Earth's surface. The temperatures vary from about 90 F to 680 F (32 C to 360 C) but roughly 2/3 range in temperature from 150 F to 250 F (65.5 C to 121.1 C). The latter are the easiest to access and, therefore, the only forms being used commercially.

Ignite - To heat a gaseous mixture to the temperature at which combustion takes place. Ignition Point - The minimum temperature at which combustion of a solid or fluid can occur. Illuminance - A measure of the amount of light incident on a surface; measured in foot-candles or Lux. Impulse Turbine - A turbine that is driven by high velocity jets of water or steam from a nozzle directed to vanes or buckets attached to a wheel. (A pelton wheel is an impulse hydroturbine). Incandescent - These lights use an electrically heated filament to produce light in a vacuum or inert gas-filled bulb. Incident Solar Radiation - The amount of solar radiation striking a surface per unit of time and area. Independent Power Producer - A company or individual that is not directly regulated as a utility. These entities produce power for their own use and/or sell it to regulated utilities. Indirect Solar Gain System - A passive solar heating system in which the sun warms a heat storage element, and the heat is distributed to the interior space by convection, conduction, and radiation. Indirect Water Heater - A type of water heater that circulates water through a heat exchanger in a boiler. The heated water then flows into an insulated storage tank. Induction - The production of an electric current in a conductor by the variation of a magnetic field in its vicinity. Induction Generator - A device that converts the mechanical energy of rotation into electricity based on electromagnetic induction. An electric voltage (electromotive force) is induced in a conducting loop (or coil) when there is a change in the number of magnetic field lines (or magnetic flux) passing through the loop. When the loop is closed by connecting the ends through an external load, the induced voltage will cause an electric current to flow through the loop and load. Thus rotational energy is converted into electrical energy.

Induction Motor - A motor in which a three phase (or any multiphase) alternating current (i.e. the working current) is supplied to iron-cored coils (or windings) within the stator. As a result, a rotating magnetic field is set up, which induces a magnetizing current in the rotor coils (or windings). Interaction of the magnetic field produced in this manner with the rotating field causes rotational motion to occur. Industrial Process Heat - The thermal energy used in an industrial process. Inert Gas - A gas that does not react with other substances; e.g. argon or krypton; sealed between two sheets of glazing to decrease the U-value (increase the R-Value) of windows. Infrared Radiation - Electromagnetic radiation whose wavelengths lie in the range from 0.75 micrometer to 1000 micrometers; invisible long wavelength radiation (heat) capable of producing a thermal or photovoltaic effect, though less effective than visible light. Insolation - The solar power density incident on a surface of stated area and orientation, usually expressed as Watts per square meter or Btu per square foot per hour. Installed Capacity - The total capacity of electrical generation devices in a power station or system. Instantaneous Efficiency (of a Solar Collector) - The amount of energy absorbed (or converted) by a solar collector (or photovoltaic cell or module) over a 15 minute period. Insulation - Materials that prevent or slow down the movement of heat. Insulation Blanket - A pre-cut layer of insulation applied around a water heater storage tank to reduce standby heat loss from the tank. Insulator - A device or material with a high resistance to electricity flow. Integrated Collector/Storage (ICS) Solar Systems - ICS solar systems are also called "batch" or "breadbox" water heaters. They combine the collector and storage tank in one unit. The sun shining into the collector strikes the storage tank directly, heating the water.

The large thermal mass of the water, plus methods to reduce heat loss through the tank, prevent the stored water from freezing. Integrated Heating Systems - A type of heating appliance that performs more than one function, for example space and water heating. Integrated Resource Plan (IRP) - A plan developed by an electric utility, sometimes as required by a public regulatory commission or agency, that defines the short and long term capacity additions (supply side) and demand side management programs that it will undertake to meet projected energy demands. Interconnection - A connection or link between power systems that enables them to draw on each other's reserve capacity in time of need. Intermittent Generators - Power plants, whose output depends on a factor(s) that cannot be controlled by the power generator because they utilize intermittent resources such as solar energy or the wind. Internal Combustion Electric Power Plant - The generation of electric power by a heat engine which converts part of the heat generated by combustion of the fuel into mechanical motion to operate an electric generator. Internal Gain - The heat produced by sources of heat in a building (occupants, appliances, lighting, etc). Internal Mass - Materials with high thermal energy storage capacity contained in or part of a building's walls, floors, or freestanding elements. Internal Rate of Return - A widely used rate of return for performing economic analysis. This method solves for the interest rate that equates the equivalent worth of an alternative's cash receipts or savings to the equivalent worth of cash expenditures, including investments. The resultant interest rate is termed the internal rate of return (IRR). Interruptable Load - Energy loads that can be shut off or disconnected at the supplier's discretion or as determined by a contractual agreement between the supplier and the customer.

Intrinsic Layer - A layer of semiconductor material (as used in a solar photovoltaic device) whose properties are essentially those of the pure, undoped, material. Inverter - A device that that converts direct current electricity (from for example a solar photovoltaic module or array) to alternating current for use directly to operate appliances or to supply power to a electricity grid. Investment Tax Credit - A tax credit granted for specific types of investments. Investor Owned Utility (IOU) - A utility owned by stockholders or other investors; sometimes referred to as a private utility, in contrast to a public utility that is owned by a government agency or cooperative. Ion - An electrically charged atom or group of atoms that has lost or gained electrons; a loss makes the resulting particle positively charged; a gain makes the particle negatively charged. Ionizer - A device that removes airborne particles from breathable air. Negative ions are produced and give up their negative charge to the particles. These new negative particles are then attracted to the positive particles surrounding them. This accumulation process continues until the particles become heavy enough to fall to the ground. Irradiance - The direct, diffuse, and reflected solar radiation that strikes a surface. Isolated Solar Gain System - A type of passive solar heating system where heat is collected in one area for use in another. I-Type Semiconductor - A semiconductor material that is left intrinsic, or undoped so that the concentration of charge carriers is characteristic of the material itself rather than of added impurities. I-V Curve - A graphical plot or representation the current and voltage output of a solar photovoltaic cell or module as a load on the device is increased from short circuit (no load) condition to the open circuit condition; used to characterize cell/module performance.

Jacket - The enclosure on a water heater, furnace, or boiler. Joist - A structural, load-carrying building member with an open web system that supports floors and roofs utilizing wood or specific steels and is designed as a simple span member. Joule - A metric unit of energy or work; the energy produced by a force of one Newton operating through a distance of one meter; 1 Joule per second equals 1 Watt or 0.737 foot-pounds; 1 Btu equals 1,055 Joules. Joule's Law - The rate of heat production by a steady current in any part of an electrical circuit that is proportional to the resistance and to the square of the current, or, the internal energy of an ideal gas depends only on its temperature. Junction - A region of transition between semiconductor layers, such as a p/n junction, which goes from a region that has a high concentration of acceptors (p-type) to one that has a high concentration of donors (n-type).

Kaplan Turbine - A type of turbine that that has two blades whose pitch is adjustable. The turbine may have gates to control the angle of the fluid flow into the blades. Kerosene - A type of heating fuel derived by refining crude oil that has a boiling range at atmospheric pressure from 400 degrees to 550 degrees F. Kilovolt-Ampere (kVa) - A unit of apparent power, equal to 1,000 volt-amperes; the mathematical product of the volts and amperes in an electrical circuit. Kilowatt (kW) - A standard unit of electrical power equal to one thousand watts, or to the energy consumption at a rate of 1000 Joules per second. Kilowatt-hour - A unit or measure of electricity supply or consumption of 1,000 Watts over the period of one hour; equivalent to 3,412 Btu. Kinetic Energy - Energy available as a result of motion that varies directly in proportion to an object's mass and the square of its velocity. Kneewall - A wall usually about 3 to 4 feet high located that is placed in the attic of a home, anchored with plates between the attic floor joists and the roof joist. Sheathing can be attached to these walls to enclose an attic space.

Lagoon - In wastewater treatment or livestock facilities, a shallow pond used to store wastewater where sunlight and biological activity decompose the waste. Lamp - A light source composed of a metal base, a glass tube filled with an inert gas or a vapor, and base pins to attach to a fixture. Landscaping - Features and vegetation on the outside of or surrounding a building for aesthetics and energy conservation. Langley - A unit or measure of solar radiation; 1 calorie per square meter or 3.69 Btu per square foot. Lattice - The regular periodic arrangement of atoms or molecules in a crystal of semiconductor material. Latent Cooling Load - The load created by moisture in the air, including from outside air infiltration and that from indoor sources such as occupants, plants, cooking, showering, etc. Latent Heat - The change in heat content that occurs with a change in phase and without change in temperature. Latent Heat of Vaporization - The quantity of heat produced to change a unit weight of a liquid to vapor with no change in temperature. Law(s) of Thermodynamics - The first law states that energy can not be created or destroyed; the second law states that when a free exchange of heat occurs between two materials, the heat always moves from the warmer to the cooler material. Lead Acid Battery - An electrochemical battery that uses lead and lead oxide for electrodes and sulfuric acid for the electrolyte. Leading Edge - In reference to a wind energy conversion system, the area of a turbine blade surface that first comes into contact with the wind. Lethe - A measure of air purity that is equal to one complete air change (in an interior space). Levelized Life Cycle Cost - A total life cycle cost divided into equal amounts.

Life Cycle Cost - The sum of all the costs both recurring and nonrecurring, related to a product, structure, system, or service during its life span or specified time period. Lift - The force that pulls a wind turbine blade, as opposed to drag. Light Quality - A description of how well people in a lighted space can see to do visual tasks and how visually comfortable they feel in that space. Light-Induced Defects - Defects, such as dangling bonds, induced in an amorphous silicon semiconductor upon initial exposure to light. Light Trapping - The trapping of light inside a semiconductor material by refracting and reflecting the light at critical angles; trapped light will travel further in the material, greatly increasing the probability of absorption and hence of producing charge carriers. Line Loss (or Drop) - Electrical energy lost due to inherent inefficiencies in an electrical transmission and distribution system under specific conditions. Liquid-Based Solar Heating System - A solar heating system that uses a liquid as the heat transfer fluid. Liquid-To-Air Heat Exchanger - A heat exchanger that transfers the heat contained in a liquid heat transfer fluid to air. Liquid-To-Liquid Heat Exchanger - A heat exchanger that transfers heat contained in a liquid heat transfer fluid to another liquid. Lithium-Sulfur Battery - A battery that uses lithium in the negative electrode and a metal sulfide in the positive electrode, and the electrolyte is molten salt; can store large amounts of energy per unit weight. Live Steam - Steam available directly from a boiler under full pressure. Load - The demand on an energy producing system; the energy consumption or requirement of a piece or group of equipment.

Load Duration Curve - A curve that displays load values on the horizontal axis in descending order of magnitude against the percent of time (on the vertical axis) that the load values are exceeded. Load Factor - The ratio of average energy demand (load) to maximum demand (peak load) during a specific period. Load Forecast - An estimate of power demand at some future period. Load Leveling - The deferment of certain loads to limit electrical power demand, or the production of energy during off-peak periods for storage and use during peak demand periods. Load Management - To influence the demand on a power source. Load Profile or Shape - A curve on a chart showing power (kW) supplied (on the horizontal axis) plotted against time of occurrence (on the vertical axis) to illustrate the variance in a load in a specified time period. Load Shedding - Turning off or disconnecting loads to limit peak demand. Load Shifting - A load management objective that moves loads from on-peak periods to off-peak periods. Local Solar Time - A system of astronomical time in which the sun crosses the true north-south meridian at 12 noon, and which differs from local time according to longitude, time zone, and equation of time. Log Law - In reference to a wind energy conversion system, the wind speed profile in which wind speeds increase with the logarithmic of the height of the wind turbine above the ground. Long Ton - A unit that equals 20 long hundredweight or 2,240 pounds. Used mainly in England. Long-Wave Radiation - Infrared or radiant heat. Loose Fill Insulation - Insulation made from rockwool fibers, fiberglass, cellulose fiber, vermiculite or perlite minerals, and composed of loose fibers or granules can be applied by pouring directly from the bag or with a blower.

Losses (Energy) - A general term applied to the energy that is converted to a form that can not be effectively used (lost) during the operation of an energy producing, conducting, or consuming system. Loss of Load Probability (LOLP) - A measure of the probability that a system demand will exceed capacity during a given period; often expressed as the estimated number of days over a long period, frequently 10 years or the life of the system. Low Btu Gas - A fuel gas with a heating value between 90 and 200 Btu per cubic foot. Low-E Coatings & (Window) Films - A coating applied to the surface of the glazing of a window to reduce heat transfer through the window. Lower (Net) Heating Value - The lower or net heat of combustion for a fuel that assumes that all products of combustion are in a gaseous state. (See Net Heating Value below.) Low-Flow Solar Water Heating Systems - The flow rate in these systems is 1/8 to 1/5 the rate of most solar water heating systems. The low-flow systems take advantage of stratification in the storage tank and theoretically allows for the use of smaller diameter piping to and from the collector and a smaller pump. Low Flush Toilet - A toilet that uses less water than a standard one during flushing, for the purpose of conserving water resources. Low-Pressure Sodium Lamp - A type of lamp that produces light from sodium gas contained in a bulb operating at a partial pressure of 0.13 to 1.3 Pascal. The yellow light and large size make them applicable to lighting streets and parking lots. Lumen - An empirical measure of the quantity of light. It is based upon the spectral sensitivity of the photosensors in the human eye under high (daytime) light levels. Photometrically it is the luminous flux emitted with a solid angle (1 steradian) by a point source having a uniform luminous intensity of 1 candela. Lumens/Watt (LPW) - A measure of the efficacy (efficiency) of lamps. It indicates the amount of light (lumens) emitted by the lamp for each unit of electrical power (Watts) used.

Luminaire - A complete lighting unit consisting of a lamp(s), housing, and connection to the power circuit. Luminance - The physical measure of the subjective sensation of brightness; measured in lumens. Lux - The unit of illuminance equivalent to 1lumen per square meter.

Magma - Molten or partially molten rock at temperatures ranging from 1,260 F to 2,880 F (700 C to 1600 C). Some magma bodies are believed to exist at drillable depths within the Earth's crust, although practical technologies for harnessing magma energy have not been developed. If ever utilized, magma represents a potentially enormous resource. Magnetic Ballast - A type of florescent light ballast that uses a magnetic core to regulate the voltage of a florescent lamp. Make-Up Air - Air brought into a building from outside to replace exhaust air. Manual J - The standard method for calculating residential cooling loads developed by the Air-Conditioning and Refrigeration Institute (ARI) and the Air Conditioning Contractors of America (ACCA) based largely on the American Society of Heating, Refrigeration, and AirConditioning Engineer's (ASHRAE) "Handbook of Fundamentals." Marginal Cost - The cost of producing one additional unit of a product. Masonry - Material such as brick, rock, or stone. Masonry Stove - A type of heating appliance similar to a fireplace, but much more efficient and clean burning. They are made of masonry and have long channels through which combustion gases give up their heat to the heavy mass of the stove, which releases the heat slowly into a room. Often called Russian or Finnish fireplaces. Mass Burn Facility - A type of municipal solid waste (MSW) incineration facility in which MSW is burned with only minor presorting to remove oversize, hazardous, or explosive materials. Mass burn facilities can be large, with capacities of 3000 tons (2.7 million kg) of MSW per day or more. They can be scaled down to handle the waste from smaller communities, and modular plants with capacities as low as 25 tons (22.7 thousand kg) per day have been built. Mass burn technologies represent over 75% of all the MSW-to-energy facilities constructed in the United States to date. The major components of a mass burn facility include refuse receiving and handling, combustion and steam generation, flue gas cleaning, power generation (optional), condenser cooling water, residue ash hauling and landfilling.

MCF - An abbreviation for one thousand cubic feet of natural gas with a heat content of 1,000,000 Btus, or 10 therms. Mean Power Output (of a Wind Turbine) - The average power output of a wind energy conversion system at a given mean wind speed based on a Raleigh frequency distribution. Mean Wind Speed - The arithmetic wind speed over a specified time period and height above the ground (the majority of U.S. National Weather Service anemometers are at 20 feet (6.1 meters). Mechanical Systems - Those elements of building used to control the interior climate. Median Wind Speed - The wind speed with 50 percent probability of occurring. Medium Btu Gas - Fuel gas with a heating value of between 200 and 300 Btu per cubic foot. Medium Pressure - For valves and fittings, implies that they are suitable for working pressures between 125 to 175 pounds per square inch. Megawatt - One thousand kilowatts, or 1 million watts; standard measure of electric power plant generating capacity. Megawatt-hour - One thousand kilowatt-hours or 1 million watthours. Mercury Vapor Lamp- A high-intensity discharge lamp that uses mercury as the primary light-producing element. Includes clear, phosphor coated, and self-ballasted lamps. Met - An approximate unit of heat produced by a resting person, equal to about 18.5 Btu per square foot per hour. Metal Halide Lamp - A high-intensity discharge lamp type that uses mercury and several halide additives as light-producing elements. These lights have the best Color Rendition Index (CRI) of the HighIntensity Discharge lamps. They can be used for commercial interior lighting or for stadium lights.

Methane - A colorless, odorless, tasteless gas composed of one molecule of Carbon and four of hydrogen, which is highly flammable. It is the main constituent of "natural gas" that is formed naturally by methanogenic, anaerobic bacteria or can be manufactured, and which is used as a fuel and for manufacturing chemicals. Methanol (CH3OH; Methyl alcohol or wood alcohol) - A clear, colorless, very mobile liquid that is flammable and poisonous; used as a fuel and fuel additive, and to produce chemicals. Metric Ton (Tonne) - A unit of mass equal to 1,000 kilograms or 2,204.6 pounds. Microclimate - The local climate of specific place or habitat, as influenced by landscape features. Microgroove - A small groove scribed into the surface of a solar photovoltaic cell which is filled with metal for contacts. Micrometer - One millionth of a meter (10-6 m). Mill - A common utility monetary measure equal to one-thousandth of a dollar or a tenth of a cent. Minority Carrier - A current carrier, either an electron or a hole, that is in the minority in a specific layer of a semiconductor material; the diffusion of minority carriers under the action of the cell junction voltage is the current in a photovoltaic device. Minority Carrier Lifetime - The average time a minority carrier exists before recombination. Mixing Valve - A valve operated by a thermostat that can be installed in solar water heating systems to mix cold water with water from the collector loop to maintain a safe water temperature. Modified Degree-Day Method - A method used to estimate building heating loads by assuming that heat loss and gain is proportional to the equivalent heat-loss coefficient for the building envelope. Module - The smallest self-contained, environmentally protected structure housing interconnected photovoltaic cells and providing a single dc electrical output; also called a panel.

Moisture Content - The water content of a substance (a solid fuel) as measured under specified conditions being the: Dry Basis, which equals the weight of the wet sample minus the weight of a (bone) dry sample divided by the weight of the dry sample times 100 (to get percent); Wet Basis, which is equal to the weight of the wet sample minus the weight of the dry sample divided by the weight of the wet sample times 100. Moisture Control - The process of controlling indoor moisture levels and condensation. Monolithic - Fabricated as a single structure. Monoculture - The planting, cultivation, and harvesting of a single species of crop in a specified area. Motor - A machine supplied with external energy that is converted into force and/or motion. Motor Speed - The number of revolutions that the motor turns in a given time period (i.e. revolutions per minute, rpm). Movable Insulation - A device that reduces heat loss at night and during cloudy periods and heat gain during the day in warm weather. A movable insulator could be an insulative shade, shutter panel, or curtain. MTBE - Methyl Tertiary Butyl Ether (MTBE) is an ether compound used as a gasoline blending component to raise the oxygen content of gasoline. MTBE is made by combining isobutylene (from various refining and chemical processes) and methanol (usually made from natural gas). Multijunction Device - A high-efficiency photovoltaic device containing two or more cell junctions, each of which is optimized for a particular part of the solar spectrum. Multi-Zone System - A building heating, ventilation, and/or air conditioning system that distributes conditioned air to individual zones or rooms. Municipal Solid Waste (MSW) - Waste material from households and businesses in a community that is not regulated as hazardous.

Municipal Waste - As defined in the Energy Security Act (P.L. 96294; 1980) as "any organic matter, including sewage, sewage sludge, and industrial or commercial waste, and mixtures of such matter and inorganic refuse from any publicly or privately operated municipal waste collection or similar disposal system, or from similar waste flows (other than such flows which constitute agricultural wastes or residues, or wood wastes or residues from wood harvesting activities or production of forest products)." Municipal Waste to Energy Project (or Plant) - A facility that produces fuel or energy from municipal solid waste.

Nacelle - The cover for the gear box, drive train, generator, and other components of a wind turbine. Name Plate - A metal tag attached to a machine or appliance that contains information such as brand name, serial number, voltage, power ratings under specified conditions, and other manufacturer supplied data. National Rural Electric Cooperative Association (NRECA) - This is a national organization dedicated to representing the interests of cooperative electric utilities and the consumers they serve. Members come from the 46 states that have an electric distribution cooperative. Natural Cooling - Space cooling achieved by shading, natural (unassisted, as opposed to forced) ventilation, conduction control, radiation, and evaporation; also called passive cooling. Natural Draft - Draft that is caused by temperature differences in the air. Natural Gas - A hydrocarbon gas obtained from underground sources, often in association with petroleum and coal deposits. It generally contains a high percentage of methane, varying amounts of ethane, and inert gases; used as a heating fuel. Natural Gas Steam Reforming Production - A two step process where in the first step natural gas is exposed to a high-temperature steam to produce hydrogen, carbon monoxide, and carbon dioxide. The second step is to convert the carbon monoxide with steam to produce additional hydrogen and carbon dioxide. Natural Ventilation - Ventilation that is created by the differences in the distribution of air pressures around a building. Air moves from areas of high pressure to areas of low pressure with gravity and wind pressure affecting the airflow. The placement and control of doors and windows alters natural ventilation patterns. Net Energy Production (or Balance) - The amount of useful energy produced by a system less the amount of energy required to produce the fuel. Net Generation - Equal to gross generation less electricity consumption of a power plant.

Net (Lower) Heating Value (NHV) - The potential energy available in a fuel as received, taking into account the energy loss in evaporating and superheating the water in the fuel. Equal to the higher heating value minus 1050W where W is the weight of the water formed from the hydrogen in the fuel, and 1050 is the latent heat of vaporization of water, in Btu, at 77 degrees Fahrenheit. Net Metering - The practice of using a single meter to measure consumption and generation of electricity by a small generation facility (such as a house with a wind or solar photovoltaic system). The net energy produced or consumed is purchased from or sold to the generator, respectively, at the same price. Net Present Value - The value of a personal portfolio, product, or investment after depreciation and interest on debt capital are subtracted from operating income. It can also be thought of as the equivalent worth of all cash flows relative to a base point called the present. Nitrogen Dioxide - This compound of nitrogen and oxygen is formed by the oxidation of nitric oxide (NO) which is produced by the combustion of solid fuels. Nitrogen Oxides (NOx) - The products of all combustion processes formed by the combination of nitrogen and oxygen. Nominal Capacity - The approximate energy producing capacity of a power plant, under specified conditions, usually during periods of highest load. Nominal Price - The price paid for goods or services at the time of a transaction; a price that has not been adjusted to account for inflation. Nocturnal Cooling - The effect of cooling by the radiation of heat from a building to the night sky. Nonrenewable Fuels - Fuels that cannot be easily made or "renewed," such as oil, natural gas, and coal. Non-Utility Generator/Power Producer - A class of power generator that is not a regulated utility and that has generating plants for the purpose of supplying electric power required in the conduct of their industrial and commercial operations.

Normal Recovery Capacity - A characteristic applied to domestic water heaters that is the amount of gallons raised 100 degrees Fahrenheit per hour (or minute) under a specified thermal efficiency. N-Type Semiconductor - A semiconductor produced by doping an intrinsic semiconductor with an electron-donor impurity (e.g., phosphorous in silicon). Nuclear Energy - Energy that comes from splitting atoms of radioactive materials, such as uranium, and which produces radioactive wastes.

Occupancy Sensor - An optical, ultrasonic, or infrared sensor that turns room lights on when they detect a person's presence and off after the space is vacated. Occupied Space - The space within a building or structure that is normally occupied by people, and that may be conditioned (heated, cooled and/or ventilated). Ocean Energy Systems - Energy conversion technologies that harness the energy in tides, waves, and thermal gradients in the oceans. Ocean Thermal Energy Conversion (OTEC) - The process or technologies for producing energy by harnessing the temperature differences (thermal gradients) between ocean surface waters and that of ocean depths. Warm surface water is pumped through an evaporator containing a working fluid in a closed Rankine-cycle system. The vaporized fluid drives a turbine/generator. Cold water from deep below the surface is used to condense the working fluid. Open-Cycle OTEC technologies use ocean water itself as the working fluid. Closed-Cycle OTEC systems circulate a working fluid in a closed loop. A working 10 kilowatt, closed-cycle prototype was developed by the Pacific International Center for High Technology Research in Hawaii with U.s. Department of Energy funding, but was not commercialized. Off-Peak - The period of low energy demand, as opposed to maximum, or peak, demand. Ohms - A measure of the electrical resistance of a material equal to the resistance of a circuit in which the potential difference of 1 volt produces a current of 1 ampere. Ohm's Law - In a given electrical circuit, the amount of current in amperes (i) is equal to the pressure in volts (V) divided by the resistance, in ohms (R). Oil (fuel) - A product of crude oil that is used for space heating, diesel engines, and electrical generation. One-Axis Tracking - A system capable of rotating about one axis. One Sun - The maximum value of natural solar insolation.

On-Peak Energy - Energy supplied during periods of relatively high system demands as specified by the supplier. On-Site Generation - Generation of energy at the location where all or most of it will be used. Open Access - The ability to send or wheel electric power to a customer over a transmission and distribution system that is not owned by the generator (seller) of the power. Open-Circuit Voltage - The maximum possible voltage across a photovoltaic cell; the voltage across the cell in sunlight when no current is flowing. Open-Loop System - A heating system, such as a solar water heater or geothermal heatpump, in which the working fluid is heated and used directly; in an open-loop solar system, the domestic water is circulated in the collector loop. Operating Cycle - The processes that a work input/output system undergoes and in which the initial and final states are identical. Orientation - The alignment of a building along a given axis to face a specific geographical direction. The alignment of a solar collector, in number of degrees east or west of true south. Outage - A discontinuance of electric power supply. Outgassing - The process by which materials expel or release gasses. Outside Air - Air that is taken from the outdoors. Outside Coil - The heat-transfer (exchanger) component of a heatpump, located outdoors, from which heat is collected in the heating mode, or expelled in the cooling mode. Overhang - A building element that shades windows, walls, and doors from direct solar radiation and protects these elements from precipitation. Overload - To exceed the design capacity of a device. Ovonic - A device that converts heat or sunlight directly to electricity, invented by Standford Ovshinsky, that has a unique glass composition

that changes from an electrically non-conducting state to a semiconducting state. Oxygenates - Gasoline fuel additives such as ethanol, ETBE, or MTBE that add extra oxygen to gasoline to reduce carbon monoxide pollution produced by vehicles.

Packing Factor - The ratio of solar collector array area to actual land area. Pane (Window) - The area of glass that fits in the window frame. Panel (Solar) - A term generally applied to individual solar collectors, and typically to solar photovoltaic collectors or modules. Panel Radiator - A mainly flat surface for transmitting radiant energy. Panemone - A drag-type wind machine that can react to wind from any direction. Parabolic Aluminized Reflector Lamp - A type of lamp having a lens of heavy durable glass that focuses the light. They have longer lifetimes with less lumen depreciation than standard incandescents. Parabolic Dish - A solar energy conversion device that has a bowl shaped dish covered with a highly reflective surface that tracks the sun and concentrates sunlight on a fixed absorber, thereby achieving high temperatures, for process heating or to operate a heat (Stirling) engine to produce power or electricity. Parabolic Trough - A solar energy conversion device that uses a trough covered with a highly reflective surface to focus sunlight onto a linear absorber containing a working fluid that can be used for medium temperature space or process heat or to operate a steam turbine for power or electricity generation. Parallel - A configuration of an electrical circuit in which the voltage is the same across the terminals. The positive reference direction for each resistor current is down through the resistor with the same voltage across each resistor. Particulates - The fine liquid or solid particles contained in combustion gases. The quantity and size of particulates emitted by cars, power and industrial plants, wood stoves, etc are regulated by the U.S. Environmental Protection Agency. Parallel Connection - A way of joining photovoltaic cells or modules by connecting positive leads together and negative leads together; such a configuration increases the current, but not the voltage.

Passivation - A chemical reaction that eliminates the detrimental effect of electrically reactive atoms on a photovoltaic cell's surface. Passive/Natural Cooling - To allow or augment the natural movement of cooler air from exterior, shaded areas of a building through or around a building. Passive Solar (Building) Design - A building design that uses structural elements of a building to heat and cool a building, without the use of mechanical equipment, which requires careful consideration of the local climate and solar energy resource, building orientation, and landscape features, to name a few. The principal elements include proper building orientation, proper window sizing and placement and design of window overhangs to reduce summer heat gain and ensure winter heat gain, and proper sizing of thermal energy storage mass (for example a Trombe wall or masonry tiles). The heat is distributed primarily by natural convection and radiation, though fans can also be used to circulate room air or ensure proper ventilation. Passive Solar Heater - A solar water or space-heating system in which solar energy is collected, and/or moved by natural convection without using pumps or fans. Passive systems are typically integral collector/storage (ICS; or batch collectors) or thermosyphon systems. The major advantage of these systems is that they do not use controls, pumps, sensors, or other mechanical parts, so little or no maintenance is required over the lifetime of the system. Passive Solar Home - A house built using passive solar design techniques. Payback - The amount of time required for positive cash flows to equal the total investment costs. Peak Clipping/Shaving - The process of implementing measures to reduce peak power demands on a system. Peak Demand/Load - The maximum energy demand or load in a specified time period. Peaking Capacity - Power generation equipment or system capacity to meet peak power demands. Peaking Hydropower - A hydropower plant that is operated at maximum allowable capacity for part of the day and is either shut

down for the remainder of the time or operated at minimal capacity level. Peak Power - Power generated by a utility unit that operates at a very low capacity factor; generally used to meet short-lived and variable high demand periods. Peak Shifting - The process of moving existing loads to off-peak periods. Peak Watt - A unit used to rate the performance of a solar photovoltaic (PV) cells, modules, or arrays; the maximum nominal output of a PV device, in Watts (Wp) under standardized test conditions, usually 1000 Watts per square meter of sunlight with other conditions, such as temperature specified. Peak Wind Speed - The maximum instantaneous wind speed (or velocity) that occurs within a specific period of time or interval. Pellets - Solid fuels made from primarily wood sawdust that is compacted under high pressure to form small (about the size of rabbit feed) pellets for use in a pellet stove. Pellet Stove - A space heating device that burns pellets; are more efficient, clean burning, and easier to operate relative to conventional cord wood burning appliances. Pelton Turbine - A type of impulse hydropower turbine where water passes through nozzles and strikes cups arranged on the periphery of a runner, or wheel, which causes the runner to rotate, producing mechanical energy. The runner is fixed on a shaft, and the rotational motion of the turbine is transmitted by the shaft to a generator. Generally used for high head, low flow applications. Penstock - A component of a hydropower plant; a pipe that delivers water to the turbine. Perfluorocarbon Tracer Gas Technique (PFT) - An air infiltration measurement technique developed by the Brookhaven National Laboratory to measure changes over time (one week to five months) when determining a building's air infiltration rate. This test cannot locate exact points of infiltration, but it does reveal long-term infiltration problems.

Performance Ratings - Solar collector thermal performance ratings based on collector efficiencies, usually expressed in Btu per hour for solar collectors under standard test or operating conditions for solar radiation intensity, inlet working fluid temperatures, and ambient temperatures. Perimeter Heating - A term applied to warm-air heating systems that deliver heated air to rooms by means of registers or baseboards located along exterior walls. Permeance - A unit of measurement for the ability of a material to retard the diffusion of water vapor at 73.4 F (23 C). A perm, short for permeance, is the number of grains of water vapor that pass through a square foot of material per hour at a differential vapor pressure equal to one inch of mercury. Phase - Alternating current is carried by conductors and a ground to residential, commercial, or industrial consumers. The waveform of the phase power appears as a single continuous sine wave at the system frequency whose amplitude is the rated voltage of the power. Phase Change - The process of changing from one physical state (solid, liquid, or gas) to another, with a necessary or coincidental input or release of energy. Phase-Change Material - A material that can be used to store thermal energy as latent heat. Various types of materials have been and are being investigated such as inorganic salts, eutectic compounds, and parrafins, for a variety of applications, including solar energy storage (solar energy heats and melts the material during the day and at night it releases the stored heat and reverts to a solid state). Photobiological Hydrogen Production - A hydrogen production process that process uses algae. Under certain conditions, the pigments in certain types of algae absorb solar energy. An enzyme in the cell acts as a catalyst to split water molecules. Some of the bacteria produces hydrogen after they grow on a substrate. Photocurrent - An electric current induced by radiant energy. Photoelectric Cell - A device for measuring light intensity that works by converting light falling on, or reach it, to electricity, and then measuring the current; used in photometers.

Photoelectrochemical Cell - A type of photovoltaic device in which the electricity induced in the cell is used immediately within the cell to produce a chemical, such as hydrogen, which can then be withdrawn for use. Photoelectrolysis Hydrogen Production - The production of hydrogen using a photoelectrochemical cell. Photogalvanic Processes - The production of electrical current from light. Photon - A particle of light that acts as an individual unit of energy. Photovoltaic (Conversion) Efficiency - The ratio of the electric power produced by a photovoltaic device to the power of the sunlight incident on the device. Photovoltaic (PV; Solar) Array - A group of solar photovoltaic modules connected together. Photovoltaic (Solar) Cell - A single photovoltaic device. Photovoltaic Device - A solid-state electrical device that converts light directly into direct current electricity of voltage-current characteristics that are a function of the characteristics of the light source and the materials in and design of the device. Solar photovoltaic devices are made of various semi-conductor materials including silicon, cadmium sulfide, cadmium telluride, and gallium arsenide, and in single crystalline, multi-crystalline, or amorphous forms. Photovoltaic (Solar) Module or Panel - A solar photovoltaic product that generally consists of groups of PV cells electrically connected together to produce a specified power output under standard test conditions, mounted on a substrate, sealed with an encapsulant, and covered with a protective glazing. Maybe further mounted on an aluminum frame. A junction box, on the back or underside of the module is used to allow for connecting the module circuit conductors to external conductors. Photovoltaic Peak Watt - see Peak Watt. Photovoltaic (Solar) System - A complete PV power system composed of the module (or arrary), and balance-of-system (BOS)

components including the array supports, electrical conductors/wiring, fuses, safety disconnects, and grounds, charge controllers, inverters, battery storage, etc. Photovoltaic-Thermal (PV/T) Systems - A solar energy system that produces electricity with a PV module, and collects thermal energy from the module for heating. There are no commercially available systems available (as of 11/97). Physical Vapor Deposition - A method of depositing thin semiconductor photovoltaic) films. With this method, physical processes, such as thermal evaporation or bombardment of ions, are used to deposit elemental semiconductor material on a substrate. Pitch Control - A method of controlling a wind turbine's speed by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency. P-I-N - A semiconductor (phtovoltaic) device structure that layers an intrinsic semiconductor between a p-type semiconductor and an n-type semiconductor; this structure is most often used with amorphous silicon PV devices. P/N - A semiconductor (photovoltaic) device structure in which the junction is formed between a p-type layer and an n-type layer. Plenum - The space between a hanging ceiling and the floor above or roof; usually contains HVAC ducts, electrical wiring, fire suppression system piping, etc. Plug Flow Digester - A type of anaerobic digester that has a horizontal tank in which a constant volume of material is added and forces material in the tank to move through the tank and be digested. Point-Contact Cell - A high efficiency silicon photovoltaic concentrator cell that employs light trapping techniques and pointdiffused contacts on the rear surface for current collection. Polycrystalline - A semiconductor (photovoltaic) material composed of variously oriented, small, individual crystals. Polyethylene - A registered trademark for plastic sheeting material that can be used as a vapor retarder. This plastic is used to make

grocery bags. It is a long chain of carbon atoms with 2 hydrogen atoms attached to each carbon atom. Polystyrene (see Foam Insulation) Porous Media - A solid that contains pores; normally, it refers to interconnected pores that can transmit the flow of fluids. (The term refers to the aquifer geology when discussing sites for CAES.) Portfolio Standard - The requirement that an electric power utility generate or purchase a specified percentage of the power it supplies/sells from renewable energy resources, and thereby guarantee a market for electricity generated from renewable energy resources. Potable Water - Water that is suitable for drinking, as defined by local health officials. Potential Energy - Energy available due to position. Pound of Steam - One pound of water in vapor phase; is NOT steam pressure, which is expressed as pounds per square inch (psi). Pound Per Square Inch Absolute (psia) - A unit of pressure [hydraulic (liquid) or pneumatic (gas)] that does not include atmospheric pressure. Power - Energy that is capable or available for doing work; the time rate at which work is performed, measured in horsepower, Watts, or Btu per hour. Electric power is the product of electric current and electromotive force. Power Coefficient - The ratio of power produced by a wind energy conversion device to the power in a reference area of the free windstream. Power Conditioning - The process of modifying the characteristics of electrical power (for e.g., inverting dc to AC). Power (Output) Curve - A plot of a wind energy conversion device's power output versus wind speed. Power Density - The amount of power per unit area of a free windstream.

Power Factor (PF) - The ratio of actual power being used in a circuit, expressed in watts or kilowatts, to the power that is apparently being drawn from a power source, expressed in volt-amperes or kilovoltamperes. Power (Solar) Tower - A term used to describe solar thermal, central receiver, power systems, where an array of reflectors focus sunlight onto a central receiver and absorber mounted on a tower. Power Transmission Line - An electrical conductor/cable that carries electricity from a generator to other locations for distribution. Preheater (Solar) - A solar heating system that preheats water or air that is then heated more by another heating appliance. Present Value - The amount of money required to secure a specified cash flow at a future date at a specified return. Pressure Drop - The loss in static pressure of a fluid (liquid or gas) in a system due to friction from obstructions in pipes, from valves, fittings, regulators, burners, etc, or by a breech or rupture of the system. Pressurization Testing - A technique used by energy auditors, using a blower door, to locate areas of air infiltration by exaggerating the defects in the building shell. This test only measures air infiltration at the time of the test. It does not take into account changes in atmospheric pressure, weather, wind velocity, or any activities the occupants conduct that may affect air infiltration rates over a period of time. Primary Air - The air that is supplied to the combustion chamber of a furnace. Prime Mover - Any machine capable of producing power to do work. Process Heat - Thermal energy that is used in agricultural and industrial operations. Products of Combustion - The elements and compounds that result from the combustion of a fuel. Producer Gas - Low or medium Btu content gas, composed mainly of carbon monoxide, nitrogen(2), and hydrogen(2) made by the gasification of wood or coal.

Projected Area - The net south-facing glazing area projected on a vertical plane. Also, the solid area covered at any instant by a wind turbine's blades from the perspective of the direction of the windstream (as opposed to the swept area). Propane - A hydrocarbon gas, C3H8, occurring in crude oil, natural gas, and refinery cracking gas. It is used as a fuel, a solvent, and a refrigerant. Propane liquefies under pressure and is the major component of liquefied petroleum (LPG). Propeller (Hydro) Turbine - A turbine that has a runner with attached blades similar to a propeller used to drive a ship. As water passes over the curved propeller blades, it causes rotation of the shaft. Proximate Analysis - A commonly used analysis for reporting fuel properties; may be on a dry (moisture free) basis, as "fired", or on an ash and moisture free basis. Fractions usually reported include: volatile matter, fixed carbon, moisture, ash, and heating value (higher heating value). Psi - Pounds of pressure per square inch. Psia - Pounds/force per square inch absolute. Psig - Pounds/force per square inch gauge. Psychrometer - An instrument for measuring relative humidity by means of wet and dry-bulb temperatures. Psychrometrics - The analysis of atmospheric conditions, particularly moisture in the air. P-Type Semiconductor - A semiconductor in which holes carry the current; produced by doping an intrinsic semiconductor with an electron acceptor impurity (e.g., boron in silicon). Public Utility Holding Company Act (PUHCA) of 1935 - A law to protect consumers and investors. It placed geographic restrictions on mergers and limitations on diversification into non-utility lines of business and takeovers of electric and gas utilities, and also established regulated monopoly markets or service territories for utilities.

Public Utilities Regulatory Policy Act (PURPA) of 1978 - A law that requires electric utilities to purchase electricity produced from qualifying power producers that use renewable energy resources or are cogenerators. Utilities are required to purchase power at a rate equal to the avoided cost of generating the power themselves. (See Avoided Costs and Qualifying Facility) Public Utility or Services Commissions (PUC or PSC) - These are state government agencies responsible for the regulation of public utilities within a state or region. A state legislature oversees the PUC by reviewing changes to utility laws, rules and regulations and approving the PUC's budget. The commission usually has five Commissioners appointed by the Governor or legislature. PUCs typically regulate: electric, natural gas, water, sewer, telephone services, trucks, buses, and taxicabs within the commission's operating region. The PUC tries to balance the interests of consumers, environmentalists, utilities, and stockholders. The PUC makes sure a region's citizens are supplied with adequate, safe utility service at reasonable rates. Pulse-Width-Modulated (PWM) Wave Inverter - A type of power inverter that produce a high quality (nearly sinusoidal) voltage, at minimum current harmonics. Pumped Storage Facility - A type of power generating facility that pumps water to a storage reservoir during off-peak periods, and uses the stored water (by allowing it to fall through a hydro turbine) to generate power during peak periods. The pumping energy is typically supplied by lower cost base power capacity, and the peaking power capacity is of greater value, even though there is a net loss of power in the process. Pyranometer - A device used to measure total incident solar radiation (direct beam, diffuse, and reflected radiation) per unit time per unit area. Pyrheliometer - A device that measures the intensity of direct beam solar radiation. Pyrolysis - The transformation on a compound or material into one or more substances by heat alone (without oxidation). Often called destructive distillation. Pyrolysis of biomass is the thermal degradation of the material in the absence of reacting gases, and occus pior to or simultaneously with gasification reactions in a gasifier. Pyrolysis

products consist of gases, liquids, and char generally. The liquid fraction of pyrolisized biomass consists of an insoluble viscouse tar, and pyroligneous acids (acetic acid, methanol, acetone, esters, aldehydes, and furfural). The distribution of pyrolysis products varies depending on the feedstock composition, heating rate, temperature, and pressure.

Quad - One quadrillion Btu. (1,000,000,000,000,000 Btu) Qualifying Facility - A category of electric power producer established under the Public Utility Regulatory Policy Act (PURPA) of 1978, that includes small-power producers (SPP) who use renewable sources of energy such as biomass, geothermal, hydroelectricity, solar (thermal and photovoltaic), and wind, or cogenerators who produce both heat and electricity using any type of fuel. PURPA requires utilities to purchase electricity from these power producers at a rate approved by a state utility regulatory agency under Federal guidelines. PURPA also requires utilities to sell electricity to these producers. Some states have developed their own programs for SPPs and utilities.

Radiant Barrier - A thin, reflective foil sheet that exhibits low radiant energy transmission and under certain conditions can block radiant heat transfer; installed in attics to reduce heat flow through a roof assembly into the living space. Radiant Ceiling Panels - Ceiling panels that contain electric resistance heating elements embedded within them to provide radiant heat to a room. Radiant Energy - Energy that transmits away from its source in all directions. Radiant Floor - A type of radiant heating system where the building floor contains channels or tubes through which hot fluids such as air or water are circulated. The whole floor is evenly heated. Thus, the room heats from the bottom up. Radiant floor heating eliminates the draft and dust problems associated with forced air heating systems. Radiant Heating System - A heating system where heat is supplied (radiated) into a room by means of heated surfaces, such as electric resistance elements, hot water (hydronic) radiators, etc. Radiation - The transfer of heat through matter or space by means of electromagnetic waves. Radiative Cooling - The process of cooling by which a heat absorbing media absorbs heat from one source and radiates the heat away. Radiator - A room heat delivery (or exchanger) component of a hydronic (hot water or steam) heating system; hot water or steam is delivered to it by natural convection or by a pump from a boiler. Radiator Vent - A device that releases pressure within a radiator when the pressure inside exceeds the operating limits of the vent. Radioactive Waste - Materials left over from making nuclear energy. Radioactive waste can living organisms if it is not stored safely. Radon - A naturally occurring radioactive gas found in the U.S. in nearly all types of soil, rock, and water. It can migrate into most buildings. Studies have linked high concentrations of radon to lung cancer. Rafter - A construction element used for ceiling support.

Rammed Earth - A construction material made by compressing earth in a form; used traditionally in many areas of the world and widely throughout North Africa and the Middle East. Rankine Cycle - The thermodynamic cycle that is an ideal standard for comparing performance of heat-engines, steam power plants, steam turbines, and heat pump systems that use a condensable vapor as the working fluid; efficiency is measured as work done divided by sensible heat supplied. Rated Life - The length of time that a product or appliance is expected to meet a certain level of performance under nominal operating conditions; in a luminaire, the period after which the lumen depreciation and lamp failure is at 70% of its initial value. Rated Power - The power output of a device under specific or nominal operating conditions. Rate Schedule - A mechanism used by electric utilities to determine prices for electricity; typically defines rates according to amounts of power demanded/consumed during specific time periods. Rayleigh Frequency Distribution - A mathematical representation of the frequency or ratio that specific wind speeds occur within a specified time interval. Reactive Power - The electrical power that oscillates between the magnetic field of an inductor and the electrical field of a capacitor. Reactive power is never converted to non-electrical power. Calculated as the square root of the difference between the square of the kilovoltamperes and the square of the kilowatts. Expressed as reactive voltamperes. Real Price - The unit price of a good or service estimated from some base year in order to provide a consistent means of comparison. Recirculation Systems - A type of solar heating system that circulate warm water from storage through the collectors and exposed piping whenever freezing conditions occur; obviously a not very efficient system when operating in this mode. Receiver - The component of a central receiver solar thermal system where reflected solar energy is absorbed and converted to thermal energy.

Recirculated Air - Air that is returned from a heated or cooled space, reconditioned and/or cleaned, and returned to the space. Rectifier - An electrical device for converting alternating current to direct current. The chamber in a cooling device where water is separated from the working fluid (for example ammonia). Recuperator - A heat exchanger in which heat is recovered from the products of combustion. Recurrent Costs - Costs that are repetitive and occur when an organization produces similar goods or services on a continuing basis. Recycling - The process of converting materials that are no longer useful as designed or intended into a new product. Reflectance - The amount (percent) of light that is reflected by a surface relative to the amount that strikes it. Reflective Coatings - Materials with various qualities that are applied to glass windows before installation. These coatings reduce radiant heat transfer through the window and also reflects outside heat and a portion of the incoming solar energy, thus reducing heat gain. The most common type has a sputtered coating on the inside of a window unit. The other type is a durable "hard-coat" glass with a coating, baked into the glass surface. Reflective Window Films - A material applied to window panes that controls heat gain and loss, reduces glare, minimizes fabric fading, and provides privacy. These films are retrofitted on existing windows. Reflective Glass - A window glass that has been coated with a reflective film and is useful in controlling solar heat gain during the summer. Reflective Insulation (see also radiant barrier) - An aluminum foil fabricated insulator with backings applied to provide a series of closed air spaces with highly reflective surfaces. Reflector Lamps - A type of incandescent lamp with an interior coating of aluminum that reflects light to the front of the bulb. They are designed to spread light over specific areas.

Refraction - The change in direction of a ray of light when it passes through one media to another with differing optical densities. Refrigerant - The compound (working fluid) used in air conditioners, heat pumps, and refrigerators to transfer heat into or out of an interior space. This fluid boils at a very low temperature enabling it to evaporate and absorb heat. Refrigeration - The process of the absorption of heat from one location and its transfer to another for rejection or recuperation. Refrigeration Capacity - A measure of the effective cooling capacity of a refrigerator, expressed in Btu per hour or in tons, where one (1) ton of capacity is equal to the heat required to melt 2,000 pounds of ice in 24 hours or 12,000 Btu per hour. Refrigeration Cycle - The complete cycle of stages (evaporation and condensation) of refrigeration or of the refrigerant. Refuse-Derived Fuel (RDF) - A solid fuel produced by shredding municipal solid waste (MSW). Noncombustible materials such as glass and metals are generally removed prior to making RDF. The residual material is sold as-is or compressed into pellets, bricks, or logs. RDF processing facilities are typically located near a source of MSW, while the RDF combustion facility can be located elsewhere. Existing RDF facilities process between 100 and 3,000 tons per day. Regenerative Cooling - A type of cooling system that uses a charging and discharging cycle with a thermal or latent heat storage subsystem. Regenerative Heating - The process of using heat that is rejected in one part of a cycle for another function or in another part of the cycle. Relamping - The replacement of a non-functional or ineffective lamp with a new, more efficient lamp. Relative Humidity - A measure of the percent of moisture actually in the air compared with what would be in it if it were fully saturated at that temperature. When the air is fully saturated, its relative humidity is 100 percent. Reliability - This is the concept of how long a device or process can operate properly without needing maintenance or replacement.

Renewable Energy - Energy derived from resources that are regenerative or for all practical purposes can not be depleted. Types of renewable energy resources include moving water (hydro, tidal and wave power), thermal gradients in ocean water, biomass, geothermal energy, solar energy, and wind energy. Municipal solid waste (MSW) is also considered to be a renewable energy resource. Resistance - The inherent characteristic of a material to inhibit the transfer of energy. In electrical conductors, electrical resistance results in the generation of heat. Electrical resistance is measured in Ohms. The heat transfer resistance properties of insulation products are quantified as the R-value. Resistance Heating - A type of heating system that provides heat from the resistance of an electrical current flowing through a conductor. Resistive Voltage Drop - The voltage developed across a cell by the current flow through the resistance of the cell. Resistor - An electrical device that resists electric current flow. Resource Recovery - The process of converting municipal solid waste to energy and/or recovering materials for recycling. Restructuring - The process of changing the structure of the electric power industry from one of guaranteed monopoly over service territories, as established by the Public Utility Holding Company Act of 1935, to one of open competition between power suppliers for customers in any area. Retrofit - The process of modifying a building's structure. Return Air - Air that is returned to a heating or cooling appliance from a heated or cooled space. Return Duct - The central heating or cooling system contains a fan that gets its air supply through these ducts, which ideally should be installed in every room of the house. The air from a room will move towards the lower pressure of the return duct. Retail Wheeling - A term for the process of transmitting electricity over transmission lines not owned by the supplier of the electricity to a retail customer of the supplier. With retail wheeling, an electricity

consumer can secure their own supply of electricity from a broker or directly from the generating source. The power is then wheeled at a fixed rate, or at a regulated "non-discriminatory" rate set by a utility commission. Reversing Valve - A component of a heat pump that reverses the refrigerant's direction of flow, allowing the heat pump to switch from cooling to heating or heating to cooling. R-Factor - See R-Value. Ribbon (Photovoltaic) Cells - A type of solar photovoltaic device made in a continuous process of pulling material from a molten bath of photovoltaic material, such as silicon, to form a thin sheet of material. Rigid Insulation Board - An insulation product made of a fibrous material or plastic foams, pressed or extruded into board-like forms. It provides thermal and acoustical insulation strength with low weight, and coverage with few heat loss paths. Rock Bin - A container that holds rock used as the thermal mass to store solar energy in a solar heating system. Rock Wool - A type of insulation made from virgin basalt, an igneous rock, and spun into loose fill or a batt. It is fire resistant and helps with soundproofing. Roof - A building element that provides protection against the sun, wind, and precipitation. Roof Pond - A solar energy collection device consisting of containers of water located on a roof that absorb solar energy during the day so that the heat can be used at night or that cools a building by evaporation at night. Roof Ventilator - A stationary or rotating vent used to ventilate attics or cathedral ceilings; usually made of galvanized steel, or polypropylene. Rotor - An electric generator consists of an armature and a field structure. The armature carries the wire loop, coil, or other windings in which the voltage is induced, whereas the field structure produces the magnetic field. In small generators, the armature is usually the rotating component (rotor) surrounded by the stationary field structure

(stator). In large generators in commercial electric power plants the situation is reversed. In a wind energy conversion device, the blades and rotating components. Run-of-River Hydropower - A type of hydroelectric facility that uses the river flow with very little alteration and little or no impoundment of the water. Rural Electrification Administration (REA) - An agency of the U.S. Dept. of Agriculture that makes loans to states and territories in the U.S. for rural electrification and the furnishing of electric energy to persons in rural areas who do not receive central station service. It also furnishes and improves electric and telephone service in rural areas, assists electric borrowers to implement energy conservation programs and on-grid and off-grid renewable energy systems, and studies the condition and progress of rural electrification. R-Value - A measure of the capacity of a material to resist heat transfer. The R-Value is the reciprocal of the conductivity of a material (U-Value). The larger the R-Value of a material, the greater its insulating properties.

Sacrificial Anode - A metal rod placed in a water heater tank to protect the tank from corrosion. Anodes of aluminum, magnesium, or zinc are the more frequently metals. The anode creates a galvanic cell in which magnesium or zinc will be corroded more quickly than the metal of the tank giving the tank a negative charge and preventing corrosion. Salt Gradient Solar Ponds - Consist of three main layers. The top layer is near ambient and has low salt content. The bottom layer is hot, typically 160 F to 212 F (71 C to 100 C), and is very salty. The important gradient zone separates these zones. The gradient zone acts as a transparent insulator, permitting the sunlight to be trapped in the hot bottom layer (from which useful heat is withdrawn). This is because the salt gradient, which increases the brine density with depth, counteracts the buoyancy effect of the warmer water below (which would otherwise rise to the surface and lose its heat to the air). An organic Rankine cycle engine is used to convert the thermal energy to electricity. Scribing - The cutting of a grid pattern of grooves in a semiconductor material, generally for the purpose of making interconnections. Sealed Combustion Heating System - A heating system that uses only outside air for combustion and vents combustion gases directly to the outdoors. These systems are less likely to backdraft and to negatively affect indoor air quality. Seasonal Energy Efficiency Ratio (SEER) - A measure of seasonal or annual efficiency of a central air conditioner or air conditioning heat pump. It takes into account the variations in temperature that can occur within a season and is the average number of Btu of cooling delivered for every watt-hour of electricity used by the heat pump over a cooling season. Seasonal Performance Factor (SPF) - Ratio of useful energy output of a device to the energy input, averaged over an entire heating season. Seasoned Wood - Wood, used for fuel, that has been air dried so that it contains 15 to 20 percent moisture content (wet basis). Seebeck Effect - The generation of an electric current, when two conductors of different metals are joined at their ends to form a circuit, with the two junctions kept at different temperatures.

Second Law Efficiency - The ratio of the minimum amount of work or energy required to perform a task to the amount actually used. Second Law of Thermodynamics - This law states that no device can completely and continuously transform all of the energy supplied to it into useful energy. Selective Absorber - A solar absorber surface that has high absorbtance at wavelengths corresponding to that of the solar spectrum and low emittance in the infrared range. Selective Surface Coating - A material with high absorbtance and low emittance properties applied to or on solar absorber surfaces. Semiconductor - Any material that has a limited capacity for conducting an electric current. Certain semiconductors, including silicon, gallium arsenide, copper indium diselenide, and cadmium telluride, are uniquely suited to the photovoltaic conversion process. Sensible Cooling Effect - The difference between the total cooling effect and the dehumidifying effect. Sensible Cooling Load - The interior heat gain due to heat conduction, convection, and radiation from the exterior into the interior, and from occupants and appliances. Sensible Heat - The heat absorbed or released when a substance undergoes a change in temperature. Sensible Heat Storage - A heat storage system that uses a heat storage medium, and where the additional or removal of heat results in a change in temperature. Series - A configuration of an electrical circuit in which the positive lead is connected to the negative lead of another energy producing, conducting, or consuming device. The voltages of each device are additive, whereas the current is not. Series Connection - A way of joining photovoltaic cells by connecting positive leads to negative leads; such a configuration increases the voltage.

Series Resistance - Parasitic resistance to current flow in a cell due to mechanisms such as resistance from the bulk of the semiconductor material, metallic contacts, and interconnections. Setback Thermostat - A thermostat that can be set to automatically lower temperatures in an unoccupied house and raise them again before the occupant returns. Shading Coefficient - A measure of window glazing performance that is the ratio of the total solar heat gain through a specific window to the total solar heat gain through a single sheet of double-strength glass under the same set of conditions; expressed as a number between 0 and 1. Sheathing - A construction element used to cover the exterior of wall framing and roof trusses. Short Circuit - An electric current taking a shorter or different path than intended. Short Circuit Current - The current flowing freely through an external circuit that has no load or resistance; the maximum current possible. Shutter - An interior or exterior movable panel that operates on hinges or slides into place, used to protect windows or provide privacy. Siding - A construction element applied to the outermost surface of an exterior wall. Sigma Heat - The sum of sensible heat and latent heat in a substance above a base temperature, typically 32 degrees Fahrenheit. Silicon - A chemical element, of atomic number 14, that is semimetallic, and an excellent semiconductor material used in solar photovoltaic devices; commonly found in sand. Simple CS (Caulk and Seal) - A technique for insulating and sealing exterior walls that reduces vapor diffusion through air leakage points by installing pre-cut blocks of rigid foam insulation over floor joists, sheet subfloor, and top plates before drywall is installed. Sine Wave - The type of alternative current generated by alternating current generators, rotary inverters, and solid-state inverters.

Single-Crystal Material - In reference to solar photovoltaic devices, a material that is composed of a single crystal or a few large crystals. Single Glaze or Pane - One layer of glass in a window frame. It has very little insulating value (R-1) and provides only a thin barrier to the outside and can account for considerable heat loss and gain. Single-phase - A generator with a single armature coil, which may have many turns and the alternating current output consists of a succession of cycles. Sizing - The process of designing a solar system to meet a specified load given the solar resource and the nominal or rated energy output of the solar energy collection or conversion device. Skylight - A window located on the roof of a structure to provide interior building spaces with natural daylight, warmth, and ventilation. Slab - A concrete pad that sits on gravel or crushed rock, wellcompacted soil either level with the ground or above the ground. Slab on Grade - A slab floor that sits directly on top of the surrounding ground. Smart Window - A term used to describe a technologically advanced window system that contains glazing that can change or switch its optical qualities when a low voltage electrical signal is applied to it, or in response to changes in heat or light. Sodium Lights - A type of high intensity discharge light that has the most lumens per watt of any light source. Soffit - A panel which covers the underside of an roof overhang, cantilever, or mansard. Solar Access or Rights - The legal issues related to protecting or ensuring access to sunlight to operate a solar energy system, or use solar energy for heating and cooling. Solar Altitude Angle - The angle between a line from a point on the earth's surface to the center of the solar disc, and a line extending horizontally from the point.

Solar Air Heater - A type of solar thermal system where air is heated in a collector and either transferred directly to the interior space or to a storage medium, such as a rock bin. Solar Array - A group of solar collectors or solar modules connected together. Solar Azimuth - The angle between the sun's apparent position in the sky and true south, as measured on a horizontal plane. Solar Cell - A solar photovoltaic device with a specified area. Solar Collector - A device used to collect, absorb, and transfer solar energy to a working fluid. Solar Constant - The average amount of solar radiation that reaches the earth's upper atmosphere on a surface perpendicular to the sun's rays; equal to 1353 Watts per square meter or 492 Btu per square foot. Solar Cooling - The use of solar thermal energy or solar electricity to power a cooling appliance. There are five basic types of solar cooling technologies: absorption cooling, which can use solar thermal energy to vaporize the refrigerant; desiccant cooling, which can use solar thermal energy to regenerate (dry) the desiccant; vapor compression cooling, which can use solar thermal energy to operate a Rankinecycle heat engine; and evaporative coolers ("swamp" coolers), and heat-pumps and air conditioners that can by powered by solar photovoltaic systems. Solar Declination - The apparent angle of the sun north or south of the eath's equatorial plane. The earth's rotation on its axis causes a daily change in the declination. Solar Distillation - The process of distilling (purifying) water using solar energy. Water can be placed in an air tight solar collector with a sloped glazing material, and as it heats and evaporates, distilled water condenses on the collector glazing, and runs down where it can be collected in a tray. Solar Energy - Electromagnetic energy transmitted from the sun (solar radiation). The amount that reaches the earth is equal to one billionth of total solar energy generated, or the equivalent of about 420 trillion kilowatt-hours.

Solar Energy Industries Association (SEIA) - A national trade association of solar energy equipment manufacturers, retailers, suppliers, installers, and consultants. Solar Energy Research Institute (SERI) - A federally funded institute, created by the Solar Energy Research, Development and Demonstration Act of 1974, that conducted research and development of solar energy technologies. Became the National Renewable Energy Laboratory (NREL) in 1991. Solar Film - A window glazing coating, usually tinted bronze or gray, used to reduce building cooling loads, glare, and fabric fading. Solar Fraction - The percentage of a building's seasonal energy requirements that can be met by a solar energy device(s) or system(s). Solar Furnace - A device that achieves very high temperatures by the use of reflectors to focus and concentrate sunlight onto a small receiver. Solar Gain - The amount of energy that a building absorbs due to solar energy striking its exterior and conducting to the interior or passing through windows and being absorbed by materials in the building. Solar Irradiation - The amount of solar radiation, both direct and diffuse, received at any location. Solarium - A glazed structure, such as greenhouse or "sunspace." Solar Mass - A term used for materials used to absorb and store solar energy. Solar Module (Panel) - A solar photovoltaic device that produces a specified power output under defined test conditions, usually composed of groups of solar cells connected in series, in parallel, or in series-parallel combinations. Solar Noon - The time of the day, at a specific location, when the sun reaches its highest, apparent point in the sky; equal to true or due, geographic south.

Solar One - A solar thermal electric central reciever power plant ("power tower") located in Barstow, California, and completed in 1981. The Solar One had a design capacity of 10,000 peak kilowatts, and was composed of a receiver located on the top of a tower surrounded by a field of reflectors. The concentrated sunlight created steam to drive a steam turbine and electric generator located on the ground. Solar Pond - A body of water that contains brackish (highly saline) water that forms layers of differing salinity (stratifies) that absorb and trap solar energy. Solar ponds can be used to provide heat for industrial or agricultural processes, building heating and cooling, and to generate electricity. Solar Power Satellite - A solar power station investigated by NASA that entailed a satellite in geosynchronous orbit that would consist of a very large array of solar photovoltaic modules that would convert solar generated electricity to microwaves and beam them to a fixed point on the earth. Solar Panel - See Solar Module. Solar Radiation - A general term for the visible and near visible (ultraviolet and near-infrared) electromagnetic radiation that is emitted by the sun. It has a spectral, or wavelength, distribution that corresponds to different energy levels; short wavelength radiation has a higher energy than long-wavelength radiation. Solar Simulator - An apparatus that replicates the solar spectrum, and used for testing solar energy conversion devices. Solar Space Heater - A solar energy system designed to provide heat to individual rooms in a building. Solar Spectrum - The total distribution of electromagnetic radiation emanating from the sun. The different regions of the solar spectrum are described by their wavelength range. The visible region extends from about 390 to 780 nanometers (a nanometer is one billionth of one meter). About 99 percent of solar radiation is contained in a wavelength region from 300 nm (ultraviolet) to 3,000 nm (nearinfrared). The combined radiation in the wavelength region from 280 nm to 4,000 nm is called the broadband, or total, solar radiation. Solar Thermal Electric Systems - Solar energy conversion technologies that convert solar energy to electricity, by heating a

working fluid to power a turbine that drives a generator. Examples of these systems include central receiver systems, parabolic dish, and solar trough. Solar Thermal Parabolic Dishes - A solar thermal technology that uses a modular mirror system that approximates a parabola and incorporates two-axis tracking to focus the sunlight onto receivers located at the focal point of each dish. The mirror system typically is made from a number of mirror facets, either glass or polymer mirror, or can consist of a single stretched membrane using a polymer mirror. The concentrated sunlight may be used directly by a Stirling, Rankine, or Brayton cycle heat engine at the focal point of the receiver or to heat a working fluid that is piped to a central engine. The primary applications include remote electrification, water pumping, and gridconnected generation. Solar Thermal Systems - Solar energy systems that collect or absorb solar energy for useful purposes. Can be used to generate high temperature heat (for electricity production and/or process heat), medium temperature heat (for process and space/water heating and electricity generation), and low temperature heat (for water and space heating and cooling). Solar Time - The period marked by successive crossing of the earth's meridian by the sun; the hour angle of the sun at a point of observance (apparent time) is corrected to true (solar) time by taking into account the variation in the earth's orbit and rate of rotation. Solar time and local standard time are usually different for any specific location. Solar Trough Systems (see also Parabolic Trough, above) - A type of solar thermal system where sunlight is concentrated by a curved reflector onto a pipe containing a working fluid that can be used for process heat or to produce electricity. The world's largest solar thermal electric power plants use solar trough technology. They are located in California, and have a combined electricity generating capacity of 240,000 kilowatts. Solar Transmittance - The amount of solar energy that passes through a glazing material, expressed as a percentage. Solar Two - Solar Two is a retrofit of the Solar One project (see above). It is demonstrating the technical feasibility and power potential of a solar power tower using advanced molten-salt

technology to store energy. Solar Two retains several of the main components of Solar One, including the receiver tower, turbine, generator, and the 1,818 heliostats. Solenoid - An electromechanical device composed of a coil of wire wound around a cylinder containing a bar or plunger, that when a current is applied to the coil, the electromotive force causes the plunger to move; a series of coils or wires used to produce a magnetic field. Solenoid Valve - An automatic valve that is opened or closed by an electromagnet. Solid Fuels - Any fuel that is in solid form, such as wood, peat, lignite, coal, and manufactured fuels such as pulverized coal, coke, charcoal, briquettes, pellets, etc. Solidity - In reference to a wind energy conversion device, the ratio of rotor blade surface area to the frontal, swept area that the rotor passes through. Solstice - The two times of the year when the sun is apparently farthest north and south of the earth's equator; usually occurring on or around June 21 (summer solstice in northern hemisphere, winter solstice for southern hemisphere) and December 21 (winter solstice in northern hemisphere, summer solstice for the southern hemisphere). Space Heater - A moveable or fixed heater used to heat individual rooms. Spacer (Window) - Strips of material used to separate multiple panes of glass within the windows. Specific Heat - The amount of heat required to raise a unit mass of a substance through one degree, expressed as a ratio of the amount of heat required to raise an equal mass of water through the same range. Specific Heat Capacity - The quantity of heat required to change the temperature of one unit weight of a material by one degree. Specific Humidity - The weight of water vapor, per unit weight of dry air.

Specific Volume - The volume of a unit weight of a substance at a specific temperature and pressure. Spectral Energy Distribution - A curve illustrating the variation or spectral irradiance with wavelength. Spectral Irradiance - The monochromatic irradiance of a surface per unit bandwidth at a particular wavelength, usually expressed in Watts per square meter-nanometer bandwidth. Spectral Reflectance - The ratio of energy reflected from a surface in a given waveband to the energy incident in that waveband. Spectrum - see Solar Spectrum above. Spectrally Selective Coatings - A type of window glazing films used to block the infrared (heat) portion of the solar spectrum but admit a higher portion of visible light. Spillway - A passage for surplus water to flow over or around a dam. Spinning Reserve - Electric power plant or utility capacity on line and running at low power in excess of actual load. Split Spectrum Photovoltaic Cell - A photovoltaic device where incident sunlight is split into different spectral regions, with an optical apparatus, that are directed to individual photovoltaic cells that are optimized for converting that spectrum to electricity. Split System Air Conditioner - An air conditioning system that comes in two to five pieces: one piece contains the compressor, condenser, and a fan; the others have an evaporator and a fan. The condenser, installed outside the house, connects to several evaporators, one in each room to be cooled, mounted inside the house. Each evaporator is individually controlled, allowing different rooms or zones to be cooled to varying degrees. Spray Pyrolysis - A deposition process whereby heat is used to break molecules into elemental sources that are then spray deposited on a substrate. Spreader Stocker - A type of furnace in which fuel is spread, automatically or mechanically, across the furnace grate.

Sputtering - A process used to apply photovoltaic semi-conductor material to a substrate by a physical vapor deposition process where high-energy ions are used to bombard elemental sources of semiconductor material, which eject vapors of atoms that are then deposited in thin layers on a substrate. Square Wave Inverter - A type of inverter that produces square wave output.; consists of a DC source, four switches, and the load. The switches are power semiconductors that can carry a large current and withstand a high voltage rating. The switches are turned on and off at a correct sequence, at a certain frequency. The square wave inverter is the simplest and the least expensive to purchase, but it produces the lowest quality of power. Squirrel Cage Motors - This is another name for an induction motor. The motors consist of a rotor inside a stator. The rotor has laminated, thin flat steel discs, stacked with channels along the length. If the casting composed of bars and attached end rings were viewed without the laminations the casting would appear similar to a squirrel cage. Staebler-Wronski effect - The tendency of the sunlight to electricity conversion efficiency of amorphous silicon photovoltaic devices to degrade (drop) upon initial exposure to light. Stack - A smokestack or flue for exhausting the products of combustion from a combustion appliance. Stack (Heat) Loss - Sensible and latent heat contained in combustion gases and vapor emitted to the atmosphere. Stagnation Temperature - A condition that can occur in a solar collector if the working fluid does not circulate when sun is shining on the collector. Stall - In reference to a wind turbine, a condition when the rotor stops turning. Stand-Alone Generator - A power source/generator that operates independently of or is not connected to an electric transmission and distribution network; used to meet a load(s) physically close to the generator. Stand-Alone Inverter - An inverter that operates independent of or is not connected to an electric transmission and distribution network.

Standard Air - Air with a weight of 0.075 pounds per cubic foot with an equivalent density of dry air at a temperature of 86 degrees Fahrenheit and standard barometric pressure of 29.92 inches of mercury. Standard Conditions - In refrigeration, an evaporating temperature of 5 degrees Fahrenheit (F), a condensing temperature of 86 degrees F., liquid temperature before expansion of 77 degrees F., and suction temperature of 12 degrees F. Standard Cubic Foot - A column of gas at standard conditions of temperature and pressure (32 degrees Fahrenheit and one atmosphere). Standard Industrial Classification (SIC) Code - Standardized codes used to classify businesses by type of activity they engage in. Standby Heat Loses - A term used to describe heat energy lost from a water heater tank. Static Pressure - The force per unit area acting on the surface of a solid boundary parallel to the flow. Starting Torque - The torque at the bottom of a speed (rpm) versus torque curve. The torque developed by the motor is a percentage of the full-load or rated torque. At this torque the speed, the rotational speed of the motor as a percentage of synchronous speed is zero. This torque is what is available to initially get the load moving and begin its acceleration. Steam - Water in vapor form; used as the working fluid in steam turbines and heating systems. Steam Boiler - A type of furnace in which fuel is burned and the heat is used to produce steam. Steam Turbine - A device that converts high-pressure steam, produced in a boiler, into mechanical energy that can then be used to produce electricity by forcing blades in a cylinder to rotate and turn a generator shaft. Stirling Engine - A heat engine of the reciprocating (piston) where the working gas and a heat source are independent. The working gas is compressed in one region of the engine and transferred to another

region where it is expanded. The expanded gas is then returned to the first region for recompression. The working gas thus moves back and forth in a closed cycle. Stoichiometry - Chemical reactions, typically associated with combustion processes; the balancing of chemical reactions by providing the exact proportions of reactant compounds to ensure a complete reaction; all the reactants are used up to produce a single set of products. Stoichiometric Ratio - The ratio of chemical substances necessary for a reaction to occur completely. Storage Capacity - The amount of energy an energy storage device or system can store. Storage Hydropower - A hydropower facility that stores water in a reservoir during high-inflow periods to augment water during lowinflow periods. Storage projects allow the flow releases and power production to be more flexible and dependable. Many hydropower project operations use a combination of approaches. Storage Tank - The tank of a water heater. Storage Water Heater - A water heater that releases hot water from the top of the tank when a hot water tap is opened. To replace that hot water, cold water enters the bottom of the tank to ensure a full tank. Storm Door - An exterior door that protects the primary door. Storm Windows - Glass, plastic panels, or plastic sheets that reduce air infiltration and some heat loss when attached to either the interior or exterior of existing windows. Stranded Investment (Costs and Benefits) - An investment in a power plant or demand side management measures or programs, that become uneconomical due to increased competition in the electric power market. For example, an electric power plant may produce power that is more costly than what the market rate for electricity is, and the power plant owner may have to close the plant, even though the capital and financing costs of building the plant have not been recovered through prior sales of electricity from the plant. This is considered a Stranded Cost. Stranded Benefits are those utility

investments in measures or programs considered to benefit consumers by reducing energy consumption and/or providing environmental benefits that have to be curtailed due to increased competition and lower profit margins. Stud - A popular term used for a length of wood or steel used in or for wall framing. Substation - An electrical installation containing power conversion (and sometimes generation) equipment, such as transformers, compensators, and circuit breakers. Substrate - The physical material upon which a photovoltaic cell is applied. Sun Path Diagram - A circular projection of the sky vault onto a flat diagram used to determine solar positions and shading effects of landscape features on a solar energy system. Sunspace - A room that faces south (in the northern hemisphere), or a small structure attached to the south side of a house. Sun Tempered Building - A building that is elongated in the eastwest direction, with the majority of the windows on the south side. The area of the windows is generally limited to about 7% of the total floor area. A sun-tempered design has no added thermal mass beyond what is already in the framing, wall board, and so on. Insulation levels are generally high. Superconducting Magnetic Energy Storage (SMES) - SMES technology uses the superconducting characteristics of lowtemperature materials to produce intense magnetic fields to store energy. SMES has been proposed as a storage option to support largescale use of photovoltaics and wind as a means to smooth out fluctuations in power generation. Superconductivity - The abrupt and large increase in electrical conductivity exhibited by some metals as the temperature approaches absolute zero. Super Insulated Houses - A type of house that has massive amounts of insulation, airtight construction, and controlled ventilation without sacrificing comfort, health, or aesthetics.

Super Window - A popular term for highly insulating window with a heat loss so low it performs better than an insulated wall in winter, since the sunlight that it admits is greater than its heat loss over a 24 hour period. Supplementary Heat - A heat source, such as a space heater, used to provide more heat than that provided by a primary heating source. Supply Duct - The duct(s) of a forced air heating/cooling system through which heated or cooled air is supplied to rooms by the action of the fan of the central heating or cooling unit. Supply Side - Technologies that pertain to the generation of electricity. Swamp Cooler - A popular term used for an evaporative cooling device. Swept Area - In reference to a wind energy conversion device, the area through which the rotor blades spin, as seen when directly facing the center of the rotor blades. Synchronous Generator - An electrical generator that runs at a constant speed and draws its excitation from a power source external or independent of the load or transmission network it is supplying. Synchronous Inverter - An electrical inverter that inverts direct current electricity to alternating current electricity, and that uses another alternating current source, such as an electric power transmission and distribution network (grid), for voltage and frequency reference to provide power in phase and at the same frequency as the external power source. Synchronous Motor - A type of motor designed to operate precisely at the synchronous speed with no slip in the full-load speeds (rpm).

Tankless Water Heater - A water heater that heats water before it is directly distributed for end use as required; a demand water heater. Task Lighting - Any light source designed specifically to direct light a task or work performed by a person or machine. Temperature Coefficient (of a solar photovoltaic cell) - The amount that the voltage, current, and/or power output of a solar cell changes due to a change in the cell temperature. Temperature Humidity Index - An index that combines sensible temperature and air humidity to arrive at a number that closely responds to the effective temperature; used to relate temperature and humidity to levels of comfort. Temperature/Pressure Relief Valve - A component of a water heating system that opens at a designated temperature or pressure to prevent a possible tank, radiator, or delivery pipe rupture. Temperature Zones - Individual rooms or zones in a building where temperature is controlled separately from other rooms or zones. Tempering Valve - A valve used to mix heated water with cold in a heating system to provide a desired water temperature for end use. Tennessee Valley Authority (TVA) - A federal agency established in 1933 to develop the Tennessee river valley region of the southeastern U.S., and which is now nation's largest power producer. Termite Shield - A construction element that inhibits termites from entering building foundations and walls. Therm - A unit of heat containing 100,000 British thermal units (Btu). Thermal Balance Point - The point or outdoor temperature where the heating capacity of a heat pump matches the heating requirements of a building. Thermal Efficiency - A measure of the efficiency of converting a fuel to energy and useful work; useful work and energy output divided by higher heating value of input fuel times 100 (for percent). Thermal Energy - The energy developed through the use of heat energy.

Thermal Energy Storage - The storage of heat energy during utility off-peak times at night, for use during the next day without incurring daytime peak electric rates. Thermal Envelope Houses - An architectural design (also known as the double envelope house), sometimes called a "house-within-ahouse," that employs a double envelope with a continuous airspace of at least 6 to 12 inches on the north wall, south wall, roof, and floor, achieved by building inner and outer walls, a crawl space or subbasement below the floor, and a shallow attic space below the weather roof. The east and west walls are single, conventional walls. A buffer zone of solar-heated, circulating air warms the inner envelope of the house. The south-facing airspace may double as a sunspace or greenhouse. Thermal Mass - Materials that store heat. Thermal Storage Walls (Masonry or Water) - A thermal storage wall is a south-facing wall that is glazed on the outside. Solar heat strikes the glazing and is absorbed into the wall, which conducts the heat into the room over time. The walls are at least 8 in thick. Generally, the thicker the wall, the less the indoor temperature fluctuates. Thermal Resistance (R-Value) - This designates the resistance of a material to heat conduction. The greater the R-value the larger the number. Thermocouple - A device consisting of two dissimilar conductors with their ends connected together. When the two junctions are at different temperatures, a small voltage is generated. Thermodynamic Cycle - An idealized process in which a working fluid (water, air, ammonia, etc) successively changes its state (from a liquid to a gas and back to a liquid) for the purpose of producing useful work or energy, or transferring energy. Thermodynamics - A study of the transformation of energy from one form to another, and its practical application. (see Law(s) of Thermodynamics above). Thermoelectric Conversion - The conversion of heat into electricity by the use of thermocouples.

Thermography - A building energy auditing technique for locating areas of low insulation in a building envelope by means of a thermographic scanner. Thermophotovoltaic Cell - A device where sunlight concentrated onto a absorber heats it to a high temperature, and the thermal radiation emitted by the absorber is used as the energy source for a photovoltaic cell that is designed to maximize conversion efficiency at the wavelength of the thermal radiation. Thermopile - A large number of thermocouples connected in series. Thermosyphon - The natural, convective movement of air or water due to differences in temperature. In solar passive design a thermosyphon collector can be constructed and attached to a house to deliver heat to the home by the continuous pattern of the convective loop (or thermosyphon). Thermosyphon (Solar) Systems - Thermosyphon systems use a separate storage tank located above the collector. Liquid warmed in the collector rises naturally above the collector, where it is kept until it is needed. The liquid can be either water or a glycol solution. If the fluid is water, freeze protection is provided by electric heat. If the fluid is glycol, the heat from the glycol is transferred to water in the storage tank. Thermostat - A device used to control temperatures; used to control the operation of heating and cooling devices by turning the device on or off when a specified temperature is reached. Thin Film - A layer of semiconductor material, such as copper indium diselenide or gallium arsenide, a few microns or less in thickness, used to make solar photovoltaic cells. Three-phase Current - Alternating current in which three separate pulses are present, identical in frequency and voltage, but separated 120 degrees in phase. Tidal Power - The power available from the rise and fall of ocean tides. A tidal power plant works on the principal of a dam or barrage that captures water in a basin at the peak of a tidal flow, then directs the water through a hydroelectric turbine as the tide ebbs.

Tilt Angle (of a Solar Collector or Module) - The angle at which a solar collector or module is set to face the sun relative to a horizontal position. The tilt angle can be set or adjusted to maximize seasonal or annual energy collection. Timer - A device that can be set to automatically turn appliances (lights) off and on at set times. Timer (Water Heater) - This device can automatically turn the heater off at night and on in the morning. Tip Speed Ratio - In reference to a wind energy conversion device's blades, the difference between the rotational speed of the tip of the blade and the actual velocity of the wind. Ton (of Air Conditioning) - A unit of air cooling capacity; 12,000 Btu per hour. Topping-cycle - A means to increase the thermal efficiency of a steam electric generating system by increasing temperatures and interposing a device, such as a gas turbine, between the heat source and the conventional steam-turbine generator to convert some of the additional heat energy into electricity. Torque (Motor) - The turning or twisting force generated by an electrical motor in order for it to operate. Total Harmonic Distortion - The measure of closeness in shape between a waveform and it's fundamental component. Total Heat - The sum of the sensible and latent heat in a substance or fluid above a base point, usually 32 degrees Fahrenheit. Total Incident Radiation - The total radiation incident on a specific surface area over a time interval. Total Internal Reflection - The trapping of light by refraction and reflection at critical angles inside a semiconductor device so that it cannot escape the device and must be eventually absorbed by the semiconductor. Tracking Solar Array - A solar energy array that follows the path of the sun to maximize the solar radiation incident on the PV surface. The two most common orientations are (1) one axis where the array tracks

the sun east to west and (2) two-axis tracking where the array points directly at the sun at all times. Tracking arrays use both the direct and diffuse sunlight. Two-axis tracking arrays capture the maximum possible daily energy. Trailing Edge - The part of a wind energy conversion device blade, or airfoil, that is the last to contact the wind. Transformer - An electromagnetic device that changes the voltage of alternating current electricity. It consists of an induction coil having a primary and secondary winding and a closed iron core. Transmission - The process of sending or moving electricity from one point to another; usually defines that part of an electric utility's electric power lines from the power plant buss to the last transformer before the customer's connection. Transmission and Distribution Losses - The losses that result from inherent resistance in electrical conductors and transformation inefficiencies in distribution transformers in a transmission and distribution network. Transmission Lines - Transmit high-voltage electricity from the transformer to the electric distribution system. Traveling Grate - A furnace grate that moves fuel through the combustion chamber Trellis - An architectural feature used to shade exterior walls; usually made of a lattice of metal or wood; often covered by vines to provide additional summertime shading. Trickle (Solar) Collector - A type of solar thermal collector in which a heat transfer fluid drips out of header pipe at the top of the collector, runs down the collector absorber and into a tray at the bottom where it drains to a storage tank. Triple Pane (Window) - This represents three layers of glazing in a window with an airspace between the middle glass and the exterior and interior panes. Trombe Wall - A wall with high thermal mass used to store solar energy passively in a solar home. The wall absorbs solar energy and transfers it to the space behind the wall by means of radiation and by

convection currents moving through spaces under, in front of, and on top of the wall. True Power - The actual power rating that is developed by a motor before losses occur. True South - The direction, at any point on the earth that is geographically in the northern hemisphere, facing toward the South Pole of the earth. Essentially a line extending from the point on the horizon to the highest point that the sun reaches on any day (solar noon) in the sky. Tube (Fluorescent Light) - A fluorescent lamp that has a tubular shape. Tube-In-Plate-Absorber - A type of solar thermal collector where the heat transfer fluid flows through tubes formed in the absorber plate. Tube-Type Collector - A type of solar thermal collector that has tubes (pipes) that the heat transfer fluid flows through that are connected to a flat absorber plate. Tungsten Halogen Lamp - A type of incandescent lamp that contains a halogen gas in the bulb, which reduces the filament evaporation rate increasing the lamp life. The high operating temperature and need for special fixtures limits their use to commercial applications and for use in projector lamps and spotlights. Turbine - A device for converting the flow of a fluid (air, steam, water, or hot gases) into mechanical motion. Turn Down Ratio - The ratio of a boiler's or gasifier's maximum output to its minimum output. Two-Tank Solar System - A solar thermal system that has one tank for storing solar heated water to preheat the water in a conventional water heater. Two-Axis Tracking - A solar array tracking system capable of rotating independently about two axes (e.g., vertical and horizontal).

Ultimate Analysis - A procedure for determining the primary elements in a substance (carbon, hydrogen, oxygen, nitrogen, sulfur, and ash). Ultraviolet - Electromagnetic radiation in the wavelength range of 4 to 400 nanometers. Unglazed Solar Collector - A solar thermal collector that has an absorber that does not have a glazed covering. Solar swimming pool heater systems usually use unglazed collectors because they circulate relatively large volumes of water through the collector and capture nearly 80 percent of the solar energy available. Underground Home - A house built into the ground or slope of a hill, or which has most or all exterior surfaces covered with earth. Unitary Air Conditioner - An air conditioner consisting of one or more assemblies that move, clean, cool, and dehumidify air. Unvented Heater - A combustion heating appliance that vents the combustion by-products directly into the heated space. The latest models have oxygen-sensors that shut off the unit when the oxygen level in the room falls below a safe level. Useful Heat - Heat stored above room temperature (in a solar heating system). U-Value (see Coefficient of Heat Transmission) - The reciprocal of R-Value. The lower the number, the greater the heat transfer resistance (insulating) characteristics of the material.

Vacuum Evaporation - The deposition of thin films of semiconductor material by the evaporation of elemental sources in a vacuum. Valence Band - The highest energy band in a semiconductor that can be filled with electrons. Vapor Retarder - A material that retards the movement of water vapor through a building element (walls, ceilings) and prevents insulation and structural wood from becoming damp and metals from corroding. Often applied to insulation batts or separately in the form of treated papers, plastic sheets, and metallic foils. Variable-Speed Wind Turbines - Turbines in which the rotor speed increases and decreases with changing wind speed, producing electricity with a variable frequency. Vent - A component of a heating or ventilation appliance used to conduct fresh air into, or waste air or combustion gases out of, an appliance or interior space. Vent Damper - A device mounted in the vent connector that closes the vent when the heating unit is not firing. This traps heat inside the heating system and house rather than letting it draft up and out the vent system. Vented Heater - A type of combustion heating appliance in which the combustion gases are vented to the outside, either with a fan (forced) or by natural convection. Ventilation - The process of moving air (changing) into and out of an interior space either by natural or mechanically induced (forced) means. Ventilation Air - That portion of supply air that is drawn from outside, plus any recirculated air that has been treated to maintain a desired air quality. Vent Pipe - A tube in which combustion gases from a combustion appliance are vented out of the appliance to the outdoors. Vertical-Axis Wind Turbine (VAWT) - A type of wind turbine in which the axis of rotation is perpendicular to the wind stream and the ground.

Visible Light Transmittance - The amount of visible light that passes through the glazing material of a window, expressed as a percentage. Visible Radiation - The visible portion of the electromagnetic spectrum with wavelengths from 0.4 to 0.76 microns Volt - A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm. Voltage - The amount of electromotive force, measured in volts, that exists between two points. Volt-Ampere - A unit of electrical measurement equal to the product of a volt and an ampere.

Wafer A thin sheet of semiconductor (photovoltaic material) made by cutting it from a single crystal or ingot. Wall A vertical structural element that holds up a roof, encloses part or all of a room, or stands by itself to hold back soil. Wall Orientation - The geographical direction that the primary or largest exterior wall of a building faces. Water Jacket - A heat exchanger element enclosed in a boiler. Water is circulated with a pump through the jacket where it picks up heat from the combustion chamber after which the heated water circulates to heat distribution devices. A water jacket is also an enclosed waterfilled chamber in a tankless coiled water heater. When a faucet is turned on water flows into the water heater heat exchanger. The water in the chamber is heated and transfers heat to the cooler water in the heat exchanger and is sent through the hot water outlet to the appropriate faucet. Water Source Heat Pump - A type of (geothermal) heat pump that uses well (ground) or surface water as a heat source. Water has a more stable seasonal temperature than air thus making for a more efficient heat source. Water Turbine - A turbine that uses water pressure to rotate its blades; the primary types are the Pelton wheel, for high heads (pressure); the Francis turbine, for low to medium heads; and the Kaplan for a wide range of heads. Primarily used to power an electric generator. Water Wall - An interior wall made of water filled containers for absorbing and storing solar energy. Water Wheel - A wheel that is designed to use the weight and/or force of moving water to turn it, primarily to operate machinery or grind grain. Watt - The rate of energy transfer equivalent to one ampere under an electrical pressure of one volt. One watt equals 1/746 horsepower, or one joule per second. It is the product of Voltage and Current (amperage).

Watt-hour - A unit of electricity consumption of one Watt over the period of one hour. Wattmeter - A device for measuring power consumption. Wave Form - The shape of the phase power at a certain frequency and amplitude. Wavelength - The distance between similar points on successive waves. Wave Power - The concept of capturing and converting the energy available in the motion of ocean waves to energy. Weatherization - Caulking and weatherstripping to reduce air infiltration and exfiltration into/out of a building. Weatherstripping - A material used to seal gaps around windows and exterior doors. Wheeling - The process of transmitting electricity over one or more separately owned electric transmission and distribution systems. (See Wholesale and Retail Wheeling.) Whole House Fan - A mechanical/electrical device used to pull air out of an interior space; usually located in the highest location of a building, in the ceiling, and venting to the attic or directly to the outside. Wholesale Wheeling - The wheeling of electric power in amounts and at prices that generally have been negotiated in longterm contracts between the generator and a distributor or very large consumer of power. Wind Energy - Energy available from the movement of the wind across a landscape caused by the heating of the atmosphere, earth, and oceans by the sun. Wind Energy Conversion System (WECS) or Device - An apparatus for converting the energy available in the wind to mechanical energy that can be used to power machinery (grain mills, water pumps) and to operate an electrical generator. Wind Generator - A WECS designed to produce electricity.

Windmill - A WECS that is used to grind grain, and that typically has a high-solidity rotor; commonly used to refer to all types of WECS. Window - A generic term for a glazed opening that allows daylight to enter into a building and can be opened for ventilation. Windpower Curve - A graph representing the relationship between the power available from the wind and the wind speed. The power from the wind increases proportionally with the cube of the wind speed. Wind Power Plant - A group of wind turbines interconnected to a common utility system through a system of transformers, distribution lines, and (usually) one substation. Operation, control, and maintenance functions are often centralized through a network of computerized monitoring systems, supplemented by visual inspection. This is a term commonly used in the United States. In Europe, it is called a generating station. Windpower Profile - The change in the power available in the wind due to changes in the windspeed or velocity profile; the windpower profile is proportional to the cube of the wind speed profile. Wind Resource Assessment - The process of characterizing the wind resource, and its energy potential, for a specific site or geographical area. Wind Rose - A diagram that indicates the average percentage of time that the wind blows from different directions, on a monthly or annual basis. Wind Speed - The rate of flow of the wind undisturbed by obstacles. Wind Speed Duration Curve - A graph that indicates the distribution of wind speeds as a function of the cumulative number of hours that the wind speed exceeds a given wind speed in a year. Wind Speed Frequency Curve - A curve that indicates the number of hours per year that specific wind speeds occur. Wind Speed Profile - A profile of how the wind speed changes with height above the surface of the ground or water.

Wind Turbine - A term used for a wind energy conversion device that produces electricity; typically having one, two, or three blades. Wind Turbine Rated Capacity - The amount of power a wind turbine can produce at its rated wind speed, e.g., 100 kW at 20 mph. The rated wind speed generally corresponds to the point at which the conversion efficiency is near its maximum. Because of the variability of the wind, the amount of energy a wind turbine actually produces is a function of the capacity factor (e.g., a wind turbine produces 20% to 35% of its rated capacity over a year). Wind Velocity - The wind speed and direction in an undisturbed flow. Wingwall - A building structural element that is built onto a building's exterior along the inner edges of all the windows, and extending from the ground to the eaves. Wingwalls help ventilate rooms that have only one exterior wall which leads to poor cross ventilation. Wingwalls cause fluctuations in the natural wind direction to create moderate pressure differences across the windows. They are only effective on the windward side of the building. Wire (Electrical) - A generic term for an electrical conductor. Woodstove - A wood-burning appliance for space and/or water heating and/or cooking. Working Fluid - A fluid used to absorb and transfer heat energy. Wound Rotor Motors - A type of motor that has a rotor with electrical windings connected through slip rings to the external power circuit. An external resistance controller in the rotor circuit allows the performance of the motor to be tailored to the needs of the system and to be changed with relative ease to accommodate system changes or to vary the speed of the motor.

Yaw The rotation of a horizontal axis wind turbine around its tower or vertical axis. Yurt An octagonal shaped shelter that originated in Mongolia, and traditionally made from leather or canvas for easy transportation.

Zone An area within the interior space of a building, such as an individual room(s), to be cooled, heated, or ventilated. A zone has its own thermostat to control the flow of conditioned air into the space. Zoning The combining of rooms in a structure according to similar heating and cooling patterns. Zoning requires using more than one thermostat to control heating, cooling, and ventilation equipment.