Natural Gas and Energy Efficiency Terminology Guide

EFFECTIVE DATE

October 2, 2008

The following is a glossary of terms associated with energy efficiency and the natural gas industry. Industry terminology was compiled with help from the following sources:

Energy Solutions Center, American Gas Association, The Encyclopedia of Alternative Energy and Sustainable Living, The U.S. Green Building Council, The Building Commissioning Association, U.S. Department of Energy & Engineering Toolbox.com.

This Glossary was produced by Summer Lewis & Partners on behalf of the Energy Solutions Center Inc

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Terminology Index

All terms listed below are hyperlinked directly to the definition. Either double-click on the term you want to look up, or highlight the term and right click on it and select “open hyperlink”.

Select first Letter: A B C D E F G H I K L M N O P Q R S T U V W Y Z

Absolute Open Flow (AOF) – The number of cubic feet of gas per 24 hours that would be produced by a well if the only pressure against the face of the producing sand in the well bore were atmospheric pressure.

Absolute Pressure – Gauge pressure plus barometric pressure. Absolute pressure can be zero only in a perfect vacuum.

Absolute
Viscosity – The measure of a fluid’s tendency to resist flow, without regard to its density. By definition, the product of a fluid’s kinematic viscosity times its density.

Absolute Zero – The zero point on the absolute temperature scale. It is equal to -273.16 degrees C, or 0 degrees K (Kelvin), or -459.69 degrees F, or 0 degrees R (Rankine).

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 during the process.

Absorption – The extraction of one or more components from a mixture of gases when gases and liquids are brought into contact. The assimilation or extraction process causes (or is accompanied by) a physical or chemical change, or both, in the sorbent material.

Absorption Chiller – A type of air cooling device that uses absorption cooling to cool interior spaces. The key feature of absorption cooling equipment is that it produces cooling by using heat energy as an input, rather than by using mechanical energy. For this reason, absorption chillers are often common in facilities that had large boiler plants with excess capacity during the cooling season.

Absorption Chilling – 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 cooling is essentially an air conditioner driven not by electricity, but by a heat source such as natural gas, propane, solar-heated water, or geothermal-heated water. Because natural gas is the most common heat source for absorption cooling, it is also referred to as gas-fired cooling. Although mainly used in industrial or commercial settings, absorption coolers are now commercially available for large residential homes.

Absorption Plant – A device that removes hydrocarbon compounds from natural gas, especially casing head gas. The gas is run through oil of proper character, which absorbs the liquid constituents, which are then recovered by distillation. Note: absorption plants can also be chiller plants with absorption chillers in place.

Absorption Type Air Conditioner, Direct Fired – A self-contained device whichprovides cooling by direct application of heat in the form of hot water, steam
or exhaust gas. Direct fired are gas or oil run.

Accelerated Cost Recovery System (ACRS) – A depreciation system enacted as part of the Economic Recovery Tax Act of 1981 that allows rapid depreciation
of assets for tax purposes. It was repealed in the Tax Reform Act of 1986.

Acceptance Test – An investigation performed on an individual lot of a previously qualified product (e.g., plastic pipe) by, or under the observation of, the purchaser to establish conformity with a purchase agreement stipulating specified requirements.

Acetone Test – A process control test for PVC pipe which indicates how well the rigid vinyl compound has been fused together in the extruder. Improperly fused pipe will tend to flake when placed in anhydrous acetone.

Achievable Potential – In DSM (demand side management), an estimate of energy savings based on the assumption that all energy-efficient options will be adopted to the extent that they are cost-effective and possible through utility DSM (demand side management) programs.

Acre Feet of Water – The volume of water that would cover one acre to a depth of one foot, or 43,560 cubic feet of water, or 325,841.1 gallons of water.

Acre Foot – A unit of measurement applied to petroleum and natural gas reservoirs. It is equivalent to an acre of producing formation one foot thick.

Action Plan – A component of IRP, describing utility actions in the short-term (about two years) to meet the supply and demand objectives of the integrated resource plan.

Active Solar Energy System – A solar water or space-heating system that uses pumps or fans to circulate the fluid from the solar collectors to a storage tank subsystem. There are two basic types of active solar heating systems based on the type of fluid – either liquid or air – that is heated in the solar energy collectors. Liquid-based systems heat water or an antifreeze solution in a “hydronic” collector, whereas air-based systems heat air in an air collector.
<![if !supportLineBreakNewLine]> <![endif]>Both systems collect and absorb solar radiation, then transfer the solar heat directly to the interior space or to a torage system, from which the heat is distributed. If the system cannot provide adequate space heating, an auxiliary or back-up system provides the additional eat. Liquid systems are more often used when storage is included, and are well suited for radiant heating systems, boilers with hot water radiators, and even bsorption heat pumps and coolers. Both air and liquid systems can supplement forced air systems.

Actual Cost – In rate base determination.

Adiabatic – A term indicating that no heat is lost or gained by a material being subjected to a thermodynamic process. An adiabatic process is one in which there is no exchange of heat with the surroundings.

Adsorption – The extraction from a mixture of gases or liquids of one or more components, by surface adhesion to that material with which the gases or liquids come in contact. The adsorption or extraction process does not cause and is not accompanied by either a physical or chemical change in the sorbent material.

Advances for Construction – A deferred credit account representing cash advances paid to the utility by customers requiring the construction of facilities in their behalf. These advances are refundable — the time or extent of refund is dependent on the contract provisions of the advance (usually dependent on whether or not during a specified period the revenue from the installation warrants the refund). The unrefunded balance, if any, must be transferred to the appropriate plant account.

Affiliate d Entities Test – A test to determine if the amount paid for gas to an affiliate exceeds the amount paid in comparable first sales between non-affiliated ntities.

Affiliated Marketer – A marketer that is owned either by a distribution or transmission company, or by a corporation that also owns a distribution or transmission ompany.

After-Cooling – The process of cooling a compressed air or gas immediately after compression.

Air Change – A method of expressing the amount of air infiltration and/or ventilation of a building or room in terms of the number of building volumes or room olumes exchanged per unit of time.

Air Conditioner, Room – A factory-made encasedassembly, designed as a unit for mounting in a window, through a wall, or as aconsole, for the purpose of delivering conditioned air to an enclosed space without ducts.

Air Conditioning – The
process of heating, cooling, humidifying, filtering, drying, deodorizing, or
otherwise treating air in a room or building to maintain a specified
temperature and/or relative humidity and to remove impurities.

Air Conditioning, Central – A mechanical system that is designed to provide air conditioning, which may include cooling, heating, dehumidifying, circulation and cleaning. The air is treated by the conditioner at one or more central locations outside the space served and conveyed to and from the space by means of fans and pumps through ducts and pipes.

Air Diffuser – An air delivery device or louver so arranged as to promote mixing of the air introduced by it into a room with the room air, without causing objectionable drafts or noise.

Air Handler – An air handler, or air handling unit (often abbreviated to AHU), is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. Usually, an air handler contains a blower, heating and/or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to ductwork that distributes the conditioned air through the building, and returns it to the AHU. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served, without ductwork.

Air Heater – Combustion air (fed to burners) can be heated to approximately 500 degrees F by transferring heat from the flue gases to the air.

Air-Gas Ratio – The ratio of the air volume to the gas volume. A specified ratio is necessary to achieve a desired character of combustion.

Air Pollutants (from fossil fuel) – Carbon Dioxide, Nitrous Oxides, Sulfur oxides, Particulates, and VOC’s are by products of burning fossil fuels, and are health and environmental hazards when release in great quantities.

Air-Source Heat Pump – A heat pump that transfers heat from outdoor air to indoor air during the heating season, and works in reverse during the cooling season. Air-source heat pumps are efficient heating and cooling sources, especially in warm climates.

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Allocated Pool – A pool in which the total oil or natural gas production is restricted and allocated to various wells therein in accordance with proration schedules.

Allocation – The process of determining ownership rights to the gas delivered to a meter.

Allocation-Capacity – A process by which capacity available in a pipeline is distributed to parties in the event requests for volume (i.e., nominations) are in excess of the available space. Typically the allocation is based on service type, contract type and a company’s tariff provisions.

Allowance for Funds Used During Construction (AFUDC) – AFUDC is a component of construction costs representing net cost of borrowed funds and a reasonablerate on other funds used during the period of construction. AFUDC is capitalized until the project is placed in operation by concurrent credits to the income statement and charges to utility plant, based generally on the amount expended to date on the particular project. Effective January 1, 1977, FERC amended the Uniform System of Accounts establishing formulas for maximum allowable AFUDC rates.

Allowed Rate of Return – The rate of return that a regulatory commission allows on a rate base in establishing just and reasonable rates for a utility. It is usually based on the composite cost of financing rate base from debt, preferred stock, and common equity.

Alternate Fuels – Other fuels that can be substituted for the fuel in use. In the case of natural gas, the most common alternative fuels are distillate fuel oils, residual fuel oils, coal and wood.

Ambient Vaporizer – A vaporizer which derives energy for vaporizing and heating LNG from storage conditions to send out conditions from naturally occurring sources such as the atmosphere, sea water, or geothermal waters.

American Gas Association (AGA) – Trade group representing natural gas distributors and pipelines.

American National Standards Institute (ANSI) – The coordinating organization for America’s federated national standards system. The ANSI federation consists of nine hundred companies, large and small, and some two hundred trade, technical, professional, labor, and consumer organizations.

American National Standards Institute X12 Committee – The committee sanctioned by ANSI for developing and maintaining U.S. standards for business-to-business electronic data interchange pertaining to trade transactions, with business-to-business defined broadly to include all organizations but excluding all individual consumers.

Annual Fuel Utilization Efficiency (AFUE) – AFUE measures average annual seasonal efficiency of a gas furnace or boiler and may be expressed as total heating output divided by total energy (fuel) input.

Associated Liquids – Condensates (liquid hydrocarbons without free water) produced in conjunction with the production of gas to be transported or liquefiable hydrocarbons contained in such gas, but not including oil.

Atmosphere – The outdoor air in general. Also a mixture of gases within any specified chamber, such as heat-treating furnace.

Atomize – To reduce a liquid to a fine spray or mist. Oil is atomized into tiny droplets in order to be burned.

Attrition – Erosion of earnings on invested capital resulting from the regulatory practice of setting utility rates based on past costs during an inflationary period.

Automatic Meter Reading (AMR) – monitoring of natural gas quantities and characteristics as it passes through a specific location.

Auxiliary Devices – Devices used with a meter to provide an adjustment of the meter reading to permit obtaining special information, or to transmit information to a remote location.

Available Heat – The amount of energy that is converted into useful energy from a fuel.

Avoided Cost – The incremental cost that a utility would incur to purchase or produce an amount of gas equivalent to that saved by a DSM (demand side management) measure. Components may include energy, capacity, storage, transmission and distribution. Avoided costs are generally used to represent the benefits of utility-sponsored DSM (demand side management) programs.

Back Draft – See Down Draft

Back Pressure – Pressure against which a fluid is flowing. May be composed of friction in pipes, restrictions in pipes, valves, pressure in vessels to which fluid is flowing, hydrostatic head, or other resistance to fluid flow.

Backhaul – A transaction that results in the transportation of gas in a direction opposite of the aggregate physical flow of gas in the pipeline. This is typically
achieved when the transporting pipeline redelivers gas at a point(s) upstream from the point(s) of receipt. A backhaul condition will exist as long as the aggregate backhaul transactions total less than the aggregate forward haul transactions. A backhaul transaction can result in a delivery by non-delivery or cut back (reduction) of physical flow at a delivery point.

<![endif]>Baffles – Plates, louvers, or screens placed in the path of fluid flow to cause change in the direction of flow; these are used to promote mixing of gases or to eliminate undesirable solid or liquid particles in the fluid stream. Sometimes baffles are inserted in a flue to lengthen the travel of flue gases and increase efficiency of operation.

Balance, Gas – An instrument used for determining the specific gravity of gases.

Barometer – Instrument used for measuring atmospheric pressure.

Barrel (Oil) – A volumetric unit of measurement equivalent to 42 U.S. gallons, 9,702 cubic inches, 5.6146 cubic feet, 34.9722 Canadian Imperial gallons, 158.99 liters, or .15899 cubic meters. It is the unit of measurement commonly used to measure oil production and oil reserves within the U.S.

Base Gas – The gas required in a storage reservoir to provide the pressure to cycle the normal working storage volume.

Base Load Capacity – The power output of a power plant that can be continuously produced.

Base Load Demand – The minimum demand experienced by a power plant.

Base Pressure – The pressure used as a standard in determining gas volume. Volumes are measured at operating pressures and then corrected to base pressure volume. Base pressure is normally defined in any gas measurement contract. The standard value for natural gas in the United States is 14.73 psia, established by the American National Standards Institute as standard Z-132.1 in 1969.

Baseboard Radiator – A heat disseminating unit located at the lower perimeter of a room. Heat is supplied to these units by hot water, warm air, steam, or hot flue gases.

Basic Air or Gas Time – The time required to pass one cubic foot of air or gas through a given orifice in a flow prover at stated base conditions. This time is stamped on the prover orifice in seconds.

Benefit-Cost Ratio – The ratio of the value of a measure’s savings to its cost.

Best Available Control Technology (BACT) – A concept taken from the Clean Air Act designed to preserve air quality from degradation by requiring
facilities in some instances be controlled to the extent possible using the best available technology.

BI-Fuel – Term given to a diesel engine converted to run off a mixture of natural gas and diesel fuel as the pilot energy.

Bio-Gas – Methane produced by the decomposition or processing of organic matter.

Biomass – Biologically produced organic matter.

Biomass Conversion – Process by which biomass materials are burned for direct energy or by which such materials are converted to synthetic fuels.

Block Valve – Main transmission line valve designed to close in or shut down gas flow.

Blower – A device for forcing air or gas to flow in the desired direction at the required pressure. It may be either fan, centrifugal, or positive displacement type.

Boiler – A closed vessel in which a liquid is heated and/or vaporized. Often classified as to steam or hot water, low pressure or high pressure, capable of burning one fuel or a number of fuels.

Boiler Efficiency – The ratio of the useful heat output to the heat input, multiplied by 100 and expressed in percent.

Boiler Fuel Gas – Natural gas used as a fuel for the generation of steam (or hot water).

Boiler Pressure – The pressure of the steam of water in a boiler, depending on type, generally expressed in pounds per square inch gauge and corresponding temperature.

Boiler Rating – The rating of a steam boiler expressed as the total heat transferred by the heating surfaces in Btu per hour. It is sometimes expressed in horsepower or pounds of steam per hour.

Boiler, High Pressure – A boiler furnishing hot water at pressures in excess of 160 pounds per square inch (psi) and at temperatures in excess of 250oF (121oC) or steam at pressures in excess of 15 psi.

Boiler, Low Pressure – A boiler furnishing hot water at pressures not exceeding 160 pounds per square inch (psi) and at temperatures not more than 250oF (121oC) or steam at pressures not more than 15 psi.

Boiling Point – The highest temperature that can be reached by a liquid, under a given pressure, when heat is applied externally and evaporation occurs freely from the surface.

British Thermal Unit (BTU) – The amount of energy required to raise 1 pound of water 1 degree.

Btu per Cubic Foot – A measure of the heat available or released when one cubic foot of gas is burned.

Btu, Dry – Heating value contained in cubic foot of natural gas measured and calculated free of moisture content. Contractually, dry may be defined as less than or equal to seven pounds of water per Mcf.

Btu, Saturated – The number of Btus contained in a cubic foot of natural gas fully saturated with water under actual delivery pressure, temperature and gravity conditions. See BTU, DRY.

Building Commissioning – Building commissioning provides documented confirmation that building systems function according to criteria set forth in the project documents to satisfy the owner’s operational needs. Commissioning existing systems may require developing new functional criteria to address the owner’s current requirements for system performance.

Commissioning for Existing Buildings (sometimes referred to as retro-commissioning) is a systematic
process for investigating, analyzing, and optimizing the performance of building systems by improving their operation and maintenance to ensure their continued performance over time. This process helps make the building systems perform interactively to meet the owner’s current facility requirements.

Building Envelope – The walls, doors, windows and roof that separates the inside of a building from the outside.

Burner Capacity – The maximum Btu per hour that can be released by a burner while burning with a stable flame and satisfactory combustion. Also called burner rating.

Burner Head – The portion of the burner beyond the outlet end of the mixer tube which contains the ports.

Burner Tip – An attachment for a burner head which forms a burner port modified for a specific application. Also, a generic term that refers to the ultimate point of consumption for natural gas.

Burner Unit – An assembly of one or more burner heads receiving gas through a single set of control valves.

Burner, Automatically Lighted – Where fuel to the main burner is normally turned on and ignited automatically.

Burner, Conversion – A burner designed to supply gaseous fuel to an appliance originally designed to utilize another fuel. a. Firing Door Type – a conversion burner designed specifically for boiler or furnace firing door installation. b. Inshot Type – a conversion burner normally designed for boiler or furnace ash pit installation and fired in a horizontal position. c. Upshot Type – a conversion burner normally designed for boiler or furnace ash pit installation and fired in a vertical position at approximately grate level.

Burner, Gas – A device for the final release of air/gas, or oxygen/gas mixtures, or air and gas separately into the combustion zone. Gas burners may be classed as atmospheric burners or blast (pressure) burners.

Burner, Manually Lighted – Where fuel to the main burner is turned on only by hand and ignited under supervision.

Calibrate – To ascertain, usually by comparison with a standard, the locations at which scale or chart graduations should be placed to correspond to a series of values of the quantity which the instrument is to measure, receive or transmit. Also, to adjust the output of a device, to bring it to a desired value, within aspecified tolerance for a particular value of the input. Also, to ascertain the error in the output of a device by checking it against a standard.

Calorimeter – An apparatus for measuring the amount of heat released by the combustion of a compound or mixture.

Capacity Factor – The ratio of the actual sales during any specified period to the maximum amount of sales the system is capable of delivering during that time.

Capital Cost – The cost of field development and plant construction and the equipment required for the generation of a power plant.

Carbon Dioxide (CO2) – A gas which is a product of combustion resulting when carbon unites with sufficient oxygen to producecomplete combustion; acomponent of many natural gases.

Carbon Monoxide (CO) – A poisonous, combustible gas formed by incomplete combustion of carbon, or reduction of carbon dioxide.

Carbon/Hydrogen Ratio – The ratio, either on a weight or on a molecular basis, of carbon-to-hydrogen in a hydrocarbon material. Materials with a high carbon/hydrogen ratio (e.g., coal) are solid. The ratio is useful as a preliminary indication of the hydrogen quantity needed toconvert the hydrocarbon to a gas and/or liquid.

Ceiling Panel Heating – A system using ceiling panels as heating surfaces. Such panels can be heated by embedding hot-water pipes, warm air ducts, or electric resistance units in the panels.

Ceiling Price – The maximum lawful price which may be charged for regulated gas.

Ceramic Radiants – Baked clay devices which become incandescent and radiate heat released to them by a gas flame.

Chill Factor – The temperature (at zero wind velocity) which would produce the same chilling effect as a particular combination of temperature and wind velocity.

Chimney Connector – The pipe which connects a fuel burning appliance to a chimney.

Chimney Effect – The tendency of air or gas in a duct, vertical passage, or building to rise when heated due to its lower density compared to the surrounding air or gas.

Circulated Gas-Oil Ratio – The number of cubic feet ofgas introduced into the well for gas-lift operations, per barrel of oil lifted.

Class of Service – Defines the type of customer. The common classes of service applied to ultimate consumers, and considerably more completely described in the A.G.A. publication “Definitions of a Gas Customer and Classes of Service for IndustryReporting Purposes”, are: 1.Residential Service: Covers service to
customers for domestic purposes (single, multifamily, or mobile homes, etc.). In residential service, the number of housing units within a structure determines the customer classification. 2.Commercial Service: Covers service to customers engaged in wholesale or retail trade, agriculture, communications, finance, fisheries, forestry, government, insurance, real estate, transportation, etc., and to customers not directly involved in other classes ofservice. 3.Industrial Service: Covers service to customers engaged primarily in a process which either involves the extraction of raw materials from the earth or a change of raw unfinished materials into another form or product.

Classification of Costs – A two step process to take functionalized costs and (1) determine whether they are fixed or variable and then (2) determine whether the fixed costs will be recovered through the demand rate or the commodity rate.

Clear Gas – Tar free gasoccurring between the carbonization and gasification zones in a coal gasification plant.

Climate Change – A change in the “average weather” that a region experiences. Average weather includes all the features associated with weather such as temperature, wind patterns and precipitation. A natural system known as the greenhouse effect regulates the temperature
on Earth. Human activities have the potential to disrupt the balance of this systemby increasing the amount of heat-trapping gases in the atmosphere which enhances the warming capability of the natural greenhouse effect.

Co-Firing – The process of burning natural gas in conjunction with another fuel.

Coal Gas – Manufactured gas made by distillation or carbonization of coal in a closed coal gas retort,coke oven, or other vessel.

Coal Gasification – Acontrolled process of reacting coal, steam, and oxygen under pressure and
elevated temperature. The crude gas is purified and has a low heating value. Subsequent catalytic upgrading can be employed to produce high-Btu pipeline grade gas.

Coal Liquefication (Coal Hydrogenation) – The conversion of coal into liquid hydrocarbons and related compounds by hydrogenation.

Coefficient of Expansion – The change in length per unit length or the change in volume per unit volume, perdegree change in temperature.&nnbsp;

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 one square foot of material in one hour. It is the reciprocal of the R-value (i.e. U-value = 1/R-value). The lower the number, the greater the heat transfer resistance (insulating)characteristics of the material.

Coefficient of Performance (COP) – A ratio of the work or useful energy outputof a system versus the amount of work or energy put in to the system as
determined by using the same energy equivalents for energy in and out. COP is used as a measure of the steady state performance or energy efficiency of heating, cooling, and refrigeration appliances. It is equal to the energy efficiency ratio (EER) divided by 3.412. The higher the COP, the more efficient the device.

Cogeneration – The use of a single prime fuel source in a reciprocating engine or gas turbine to
generate electrical and thermal energy in order to optimize the efficiency of the fuel used. The dominant demand for energy can be either electrical or
thermal. Usually it is the latter with excess electrical energy, if any, being transmitted into the local power supply company’s lines (with a reciprocal
situation existing when electrical demands exceed the cogeneration plant’s output). A parallel exists with total energy plants, which are typically
designed for the electrical demands rather than thermal. Under the 1978 Public Utility Regulatory Policies Act (PURPA), regulated utilities are required to
purchase electricity furnished by cogenerators and small power producers at rates set by regulatory bodies having jurisdiction over the utility receiving the electricity based on “full avoided cost.”

Coincident Demand – The sum of the simultaneous demands of a group of consumers.

Combination Utility – Utility which supplies both gas and some other utility service (electricity, water, etc.). For purposes of A.G.A. statistics, a combination utility derives at least 5 percent but less than 95 percent of its total operating revenues from gas operation.

Combined Accounts – When two or more meters are combined for billing purposes under the following conditions: Where combinations of meter readings are specifically provided for in rate schedules. Where the maintenance of adequate service and/or where a company’soperating convenience shall require the installation.

Combined-Cycle – In a combined cycle power plant the hot exhaust gas of a gas or oil fired gas turbine is utilized to
generate steam in a separate water / steam cycle. The hot steam is expanded in a steam turbine providing power to drive a generator. The combination of gas and steam turbine cycles allows electric power generation with highest efficiency.

Combined Heat and Power (CHP) – or Building Cooling Heating and Power (BCHP) or Combined Cooling Heating and Power (CCHP), see Cogeneration.

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Combo Heater – A
single gas appliance that provides both space heating and domestic hot water. These systems are designed primarily for use as a forced air heating system, but can also be adapted for new hydronic baseboard installations.

Combustible Material – Combustible material, as pertaining to material adjacent to or in contact with heat producing appliances, chimney connectors and vent connectors, steam and hot water pipes, and warm air ducts, means material made of or surfaced with wood, compressed paper, plant fibers, or other material that will ignite and burn. Such material shall be considered as combustible even though flame proofed, fire retardant treated, or plastered.

Combustion – Rapid chemical reaction of oxygen with fuel accompanied by the production of heat, or heat and light.

Compact Fluorescent Lamp (CFL) – Lamps that combine the energy efficiency of fluorescent lighting with the convenience and popularity of incandescent fixtures. CFLs can replace incandescents that are roughly 3–4 times their wattage, saving up to 75% of the initial lighting
energy. Although CFLs cost more than comparable incandescent bulbs, they last 10–15 times as long.

Compressor – Mechanical device for increasing the pressure of a gas.

Condensate – The liquid resulting when a vapor is subjected to cooling or application of pressure. Also, liquid hydrocarbons condensed from gas and oil wells.

Condenser – A heat exchanger which removes heat from vapor causing it to condense into a liquid.

Conditional Demand Analysis – A method that is used to estimate equipment-specific energy consumption, without requiring end-use metered data for the appliances. Instead, it relies on the statistical analysis of consumption data, appliance saturation data, and other data such as demographic, household, weather, economic and market data.

Conduction, Thermal – Process of heat transfer through a material medium in which kinetic energy is transmitted by the particles of the material from particle to particle without gross displacement of the particles.

Conservation Supply Curve – A graph showing the quantity of energy savings of individual efficiency measures on the x-axis and the total cost per unit of energy saved on the y-axis.

Content of Fuel – The heat value per unit of fuel expressed in Btu as determined from tests of fuelsamples. Examples: Btu per pound of coal, per gallon of oil, per cubic foot of gas.

Contract Demand (CD) – The amount of the system’s capacity to deliver gas which a natural gas pipeline or distributor agrees to reserve for a particular customer and for which the customer agrees to pay ademand charge as specified in the applicable tariff. Also, the daily quantity of gas which asupplier agrees to furnish and for which the buyer agrees to pay, under a specific contract.

Control – A device designed to regulate the gas, air, water, and/or electrical supply to a gas-consuming or any other device.

Control Gas – That part of the main gas flow which is separated and used to actuate the automaticvalve through a moving member such as the diaphragm in a diaphragm valve.

Control, Limit – An automatic safety control responsive to changes in level, pressure, or temperature and normally set beyond the operating range for limiting the operation of the controlled equipment.

Control, Operating – A control other than a safety control or interlock, to start or regulate burner firing according to load demand and to stop or regulate fire on satisfaction of demand or upon reaching normal temperature or pressure in the device being fired. Operating controls may also actuate auxiliary equipment.

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Controls – Internal procedures to monitor the components of cost of service based on updated actual costs.

Convection – Heat transfer by the movement of fluid.

Convector – An agency of convection. In heat transfer, a surface designed to transfer its heat to a surrounding fluid largely or wholly by convection. The heated fluid may be moved mechanically or by gravity (gravity convector). Such a surface may or may not be enclosed or concealed.

Conversion to Natural Gas – Changing the gas service to ultimate customers from a fuel other than natural gas to natural gas, including
adjustment of consumers’ appliances to perform satisfactorily with natural gas. Natural gas does not necessarily mean straight natural gas; stabilizing the heat content of the sendout gas by diluent gases or enriching gases is not considered to change the basic character of natural gas. For the purpose of uniform reporting, a company should be considered a natural gas company when 95 percent of the system has been converted.

Conversion Unit – A unit consisting of a burner together with associated thermostat and safety controls, which can be used to convert heating equipment from one fuel to another.

Cooling Coil – A coil of pipe or tubing used as a heat exchanger to cool material inside or outside the coil by means of colder material passing over or through the coilrespectively.

Corrosion – Destruction of a metal by chemical or electrochemical reaction with its environment.

Corrosion Fatigue – Reduction of fatigue durability by a corrosive environment.

Corrosion Prevention – The halting or elimination of metal damage through use of protective methods anddevices.

Critical Temperature and Pressure – That temperature above which a gas cannot be liquefied by pressure alone. The pressure under which a substance may exist as a gas in equilibrium with the liquid at the critical temperature is the critical pressure.

Cubic Foot – The most common unit of measurement of gas volume. It is the amount of gas required to fill a volume of one cubic foot under stated conditions of temperature, pressure, and water vapor.

Customer Density – Number of customers in a given unit or area or on a given length of distribution line.

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Damper – A valve, or plate, used to regulate the flow of air or other gases.

Deaerator – The apparatus used to separate the dissolved gases from the condensate.

Daylighting – The use of windows and skylights to provide supplemental lighting,in the form of direct, diffuse, or reflected sunlight, for building interiors.

De-Coupling – In public utility regulation, decoupling refers to the disassociation of a utility profit’s from its sales of the energy commodity. Instead, a rate of return is aligned with meeting revenue targets, and rates are trued up or down to meet the target at the end of the adjustment period. This makes efficiency and distributed generation to operate within the utility environment.

Dedicated Gas Reserves – Gas reserves dedicated to a natural gas pipeline company by contract. For a pipeline it is the sum of all reserves dedicated to the company by contract.

Degree Day, Cooling – A measure of the need for air conditioning (cooling) based on temperature and humidity. Although cooling degree days are published for many weather stations, a specific procedure has not been generally accepted.

Degree Day, Heating – A measure of the coldness of the weather experienced, based on the extent to which the daily mean temperature falls below a reference temperature, usually 65 degrees F.

Dehumidifier – An appliance that reduces the humidity in a room by condensing moisture in the air on to a cold surface. A dehumidifier works in a similar way to an air conditioner, the main difference being that it has both its hot and cold coils in the same box. Air is drawn in by a fan and moisture from the air condenses on one set of coils much like an air conditioners evaporator coils. The water drips into a removable bucket or through a hose to a drain. The other coil warms the air, which is blown back into the room.

Dehumidify – To
reduce by any process the quantity of water vapor contained in a solid or gas.

Dekatherm – A
unit of heating value equivalent to 10 therms or 1,000,000 Btu’s.

Deliverability – The volume of gas a well, field, pipeline, or distribution system can supply in a given period of time. Also, the practical output from a storage reservoir.

Delivery Point – Point at which gas leaves a transporter’s system completing a sale or transportation service transaction between the pipeline company and a sale or transportation service customer.

Demand – The rate at which gas is delivered to or by a system, part of a system, or a piece of equipment, expressed in cubic feet or therms or multiples thereof, for a designated period of time called the demand interval. Note: the electric industry also measures demand for electricity.

Demand Day – The 24-hour period specified by a supplier-user contract for purposes of determining the purchaser’s daily quantity of gas used (e.g., 8 AM to 8 AM, etc.). This term is primarily used in pipeline-distribution company agreements. It is similar to, and usually coincides with, the distribution company “sendout day”.

Demand Diversity – The overall variation in the time at which individual demands occur.

Demand Interval – The period of time during which the energy flow is averaged in determining demand, such as 60-minute or 15-minute.

Demand Load – The rate of flow of gas required by a consumer or a group of consumers, often an average over a specified short time interval (cf/hr or Mcf/hr). Demand is the cause; load is the effect.

Demand Meters – A device which indicates or records the instantaneous, maximum or integrated (over a specified period) demand.

Demand, Average – The demand on a system or any of its parts over an interval of time, determined by dividing the total volume in therms by the number of units of time in the interval.

Demand, Billed – The amount of electric demand a consumer is being billed for.

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Demand, Coincident – The sum of two or more demands which occur in the same demand interval.

Demand, Contract – The daily quantity of gas which the supplier agrees to furnish and for which the buyer agrees to pay, under a specific contract.

Demand, Integrated – The demand averaged over a specified period, usually determined by an integrating demand meter or by the integration of a load curve. It is the average of the instantaneous demands during a specified demand interval.

Demand, Maximum – The greatest of all the demands under consideration occurring during a specified period of time.

Demand, Minimum – The smallest of all the demands under consideration occurring during a specified period of time.

Demand, Registered- The electric demand actually measured for the billing month.

Demand Side Management (DSM) – Also known as energy demand management, entails actions that influence the quantity or patterns of use of energy consumed by end users, such as actions targeting reduction of peak demand during periods when energy-supply systems are constrained. Peak demand management does not necessarily decrease total energy consumption but could be expected to reduce the need for investments in networks and/or plants.

Density – The weight of a unit of volume, usually expressed as pounds per cubic foot.

Department of Energy (U.S.DOE) – The Department of Energy is the twelfth Cabinet Position, and it consists of the Office of the Secretary of Energy and the Federal Energy Regulatory Commission. It was created on August 4, 1977 as a result of the Department of Energy Organization Act of 1977. There are many subdivisions within the DOE, but the Economic Regulatory Administration and Energy Information Administration are two groups which have significant bearing on gas utility operations.

Depreciation – Return of investment through inclusion in cost of service (and rates) of a pro rata part of the cost of property, calculated to spread the total investment cost over a certain period of time or number of units that measure the useful life of the investment. Depreciation (in the Code of Federal Regulations) is to reimburse the company for “…the loss in service value not restored by current maintenance, incurred in connection with the consumption or prospective retirement of gas plant in the course of service from causes which are known to be in current operation and against which the utility is not protected by insurance. Among the causes to be given consideration are wear and tear, decay, action of the elements, inadequacy, obsolescence, changes in the art, changes in demand and requirements of public authorities, and, in the case of a natural gas company, the exhaustion of natural resources.”

Desiccant – Any absorbent or adsorbent, liquid or solid, that will remove water or water vapor from a material. In a refrigeration circuit, the desiccant must be insoluble in the refrigerant.

Desiccant Cooling – A new and potentially clean technology that can be used to condition the internal environment of buildings without the use of harmful refrigerants. Unlike conventional air conditioning systems, which rely on electrical energy to drive the cooling cycle, desiccant cooling is an open heat driven cycle, which uses a desiccant wheel and cooling coil in tandem to achieve both cooling and dehumidification. Because it is a heat driven cycle, there is the potential to use environmentally cleaner sources of energy such as gas, hot water, waste heat or any heat source, including solar thermal energy, able to elevate the air temperature to a level adequate for reactivation.

Desiccant materials, which absorb moisture, can be dried, or regenerated, by adding heat supplied by natural gas, waste heat, or the sun. In most systems, a wheel that contains a desiccant turns slowly to pick up humidity from incoming air and discharge that humidity to the outdoors. Desiccant cooling can also be used in tandem with conventional air conditioning system in which the desiccant removes humidity and the AC system provides cooling, and in energy recovery ventilators (ERV) to dehumidify incoming fresh air in the summer.

Design Load – The maximum average rate of gas use by a group of appliances or customers over a specified short time period, usually 15 to 30 minutes.

Design Pressure – The maximum operating pressure permitted by various codes, as determined by the design procedures applicable to the material and location involved.

Differential Pressure – The pressure difference between two points in a system. For example, the difference in pressure between the upstream and downstream taps of an orifice plate, used to measure volume passing through the orifice.

Direct Contact Water Heater – Type of water heater typically used in industrial settings where products of combustion pass through the water being heated.

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.

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Direct Vent Appliance – Gas appliance designed so that all combustion air is derived directly from the outside, and all fuel gases are discharged to the outside through an exterior wall.

Direct-Fired – A heating unit in which the combustion products are mixed with the air or liquid being heated.

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Distribution – The act or process of distributing gas from the city gas or plant that portion of utility plant used for the purpose of delivering gas from the city gate or plant to the consumers, or to expenses relating to the operating and maintenance of distribution plant.

Down Draft (Back Draft) – A flow of air down the chimney or flue because of adverse draft conditions.

Draft – A difference of pressure which causes a flow of air and/or flue gases through the boiler, flue connector, breeching, flue, or chimney.

Draft Fan, Forced – A blower type fan used to force draft air to the furnace.

Draft Fan, Induced – An exhaust-type fan used to draw flue gases through the superheater, economizer,air heater and precipitator.

Draft Hood – A device built into an appliance, or made a part of the flue or vent connectorfrom an appliance, which is designed to (a) assure the ready escape of the products of combustion from the combustion chamber in the event of no draft, back draft, or stoppage beyond the draft hood; (b) prevent a back draft from entering the combustion chamber of the appliance; and (c) neutralize the effect of stack action of the chimney or gas vent upon the operation of the appliance.

Draft Regulator (Draft Stabilizer) – A device which functions to maintain a desired draft in the appliance by automatically reducing the draft to the desired value.

Draft, Mechanical – Draft that is caused by mechanical means, such as a fan.

Draft, Natural – Draft that is caused by a thermal upset in which temperature differences change the weight (pressure) of air.

Duct – A
passageway made of sheet metal or other suitable material, not necessarily leak-tight, used for conveying air or other gas at low pressures.

Duct System – A series of ducts, elbows, and connectors to convey air, or other gas at low pressure, from one location to another.

Dual Fuel – Term typically given to boilers that can run on natural gas or oil.

Economic Potential – In DSM (demand side management), an estimate of energy savings based on the assumption that all energy-efficient options will be adopted and all existing equipment will be replaced with the most efficient measure possible whenever it is cost-effective to do so, without regard to market acceptance.

Economic Regulatory Administration (ERA) – Formerly the agency in the Department of Energy charged with the responsibility for imports of natural gas. In 1989, the ERA was eliminated and its functions were transferred to the Office of Fossil Energy (FE) in the Department of Energy.

Economizer – An arrangement of tubes through which the feed water passes before entering boiler drum and flue gases leave burners. Economizers are invariably counter flow; meaning the water flows opposite to the gases, and heat of gases is transferred to the water.

Efficiency – Relating to heat, a percentage indicating the available Btu input to combustion equipment that is converted to useful purposes.

Electric Energy – Availableheat in electricity; one kilowatt hour equals 3, 412.97 Btu.

Energy Efficiency Ratio (EER) – A ratio calculated by dividing the cooling capacity in Btu per hour by the power input in watts at any given set of rating conditions. Heating Seasonal Performance Factor (HSPF) – the total heating output of a heat pump during its normal annual usage period for heating divided by the total electric power input in watt-hours during the same period. Seasonal Energy Efficiency Ratio (SEER) – the total cooling capacity of a central unitary air conditioner or unitary heat pump in Btu’s during its normal annual usage period for coolingdivided by the total electric energy input in watt-hours during the same period.

EnergyGuide – Almost all home appliances, including refrigerators, dishwashers and laundry units, display a prominent yellow-and-black EnergyGuide. The label was developed by the Federal Trade Commission. The largest number on the guide states the estimated annual operating cost of the appliance. Some equipment, such as ovens or clothes dryers, may have two large numbers – one for electric, one for natural gas. One of the most helpful features of the EnergyGuide is a sliding scale that compares the appliance to other models and brands.

ENERGYSTAR – The ENERGYSTAR logo identifies appliances as being among the most energy-efficient products in their classes. Theyusually excee minimum federal energy-use standards by a significant amount. TheEnergySta designation, developed by the U.S. Environmental Protection Agency and Department of Energy, can be found on thousands of products, ncluding windows, water heaters, furnaces, air conditioners, light bulbs, computers and more.

Electronic Data Interchange (EDI) – The computer-to-computer exchange of business documents and information through the use of standard document formats.

Electronic Data Transfer – The computer-to-computerexchange of data for business transactions.

Electronic Gas Measurement (EGM) – “Real time” monitoring of natural gas quantities, and characteristics, as it passes through a specific location.

Electronic Ignition – A spark ignition device designed to electrically initiate the combustion process.

End-Use – The actual purpose for which gas is used by the ultimate consumer to whom it isdelivered.

End-Use Metering – The direct measuring of consumption by specific end-use appliances, typically as part of load research studies or to measure the impacts of DSM (demand side management) programs.

End-User – An entity which is the ultimate consumer for natural gas. An end-user purchases the gas for consumption but not for resale purposes.

Energy Audit – A review of a customer’s energy usage, often including recommendations to alter the customer’s demand or reduce energy usage. An audit normally involves a visit to the customer’s facility.

Energy Conservation Measure – A device, material, or appliance used or installed to improve energy efficiency.

Energy Conservation Practice – Actions or practices taken to reduce energy consumption.

Energy Efficiency Program – A program aimed at reducing overall consumption, often without regard for the timing of the program-induced savings. Such savings are generally achieved by substituting technically more efficient equipment to produce the same level of end-use services with less energy.

Energy Factor – A measure of the overall efficiency of a water heater, based on its recovery efficiency, standby loss and energy input as set out in standardized Department of Energy test procedures.

Energy Information Administration (EIA) – The statistical information collection and analysis branch of the Department of Energy.

Energy
Solutions Center- The Energy Solutions Center is a technology commercialization and market development organization representing energy utilities, municipal energy authorities, and equipment manufacturers and endors. The mission of the Center is to accelerate the acceptance of and deployment of new energy-efficient, gas-fueled technologies that enhance the operations and productivity of commercial and industrial energy users, and improves comfort and reliability for residential energy users.

Engine Driven Generator – A power generator that incorporates an engine and a generator driven by the engine. The generator incorporates a sound insulation cover that allows for efficient cooling of the various internal components. A fan draws in cooling air through one or more cooling air vents to cool a battery, a DC/DC converter, an electronic module, the engine, the generator, and the muffler. The insulation cover provides quiet operation and efficient cooling of the engine-driven generator.

Environmental Protection Agency (EPA) – A federal agency created in 1970 to permit coordinated and effective governmental action, for protection of the environment by the systematic abatement and control of pollution, through integration of research monitoring, standard setting, and enforcement activities.

Equivalent Direct Radiation – Heat expressed in terms of a square foot of steam radiator surface emitting 240 Btu per hour. (Btu per hour divided by 240).

Evaporative Cooling – The adiabatic exchange of heat between air and a water spray or wetted surface. The water approaches the wet bulb temperature of the air, which remains constant during its traverse of the exchanger.

Evaporator – Equipment or device that extracts or drives out vapors from liquid solutions or gases. Also, equipment that is part of refrigerating systems to permit liquid refrigerants to evaporate in the process of absorbing heat.

Excess Air – Air
which passes through a combustion zone in excess of the quantity theoretically required for complete combustion.

Exchange Gas – Gas that is received from (or delivered to) another party in exchange for gas delivered to (or received from) such other party.

Exchange Transactions – In a gas exchange between two parties, gas is received from (or delivered to) the first party in exchange for gas delivered to (or received from) the second party. An exchange provides ameans for delivering gas supplies to a customer without the necessity o constructing and operating duplicative facilities. Central to the concept of an exchange is mutual benefits to the two parties engaging in the exchange. The transaction must involve reciprocal benefit or the trade of comparable values.

Exhaust Port – In engines, the opening through which a fluid discharges out of a cylinder. In gas meter, the openings through which gas leaves the metering chamber.

Exit Temperature – The flue gas temperature taken at the point where the gas leaves the combustion chamber.

Exothermic – That characteristic of a chemical reaction, such as fuel combustion, in which heat is liberated.

Expander Cycle – A liquefaction process using expansion turbines or engines to produce mechanical energy while refrigerating the gas to be liquefied.

Expander Turbine – A rotary motion machine employing the hot air blast of jet engines as the turning force.

Expansion Loop – Either a bend like the letter “U” or a coil in a line of pipe to provide for expansion and contraction.

Expansion Ratio – The
ratio of gas volume after expansion to the gas volume before expansion.

Expansion Valve – Aspecial valve used in refrigerating systems through which the liqui refrigerant (under high pressure) is allowed to escape into a lower pressure and thus expand into a gas.

Exterior Zones – The portions of a building, with significant amounts of exterior walls, windows, roofs, or exposed floors. Such zones have heating or cooling needs largely dependent upon weather conditions.

Federal Energy Regulatory Commission (FERC) – An agency of the government of the United States created by an Act of Congress, the Department of Energy Federal Power Commission’s interstate regulatory functions over the electric power and natural gas industries. The Act also transferred from the Interstate Commerce Commission the authority to set oil pipeline transportation rates and to set the value of oil pipelines for ratemaking purposes. In 1978, Congress passed the Natural Energy Act, broadening the FERC’s jurisdiction and
regulatory functions. The FERC now also regulates producer sales of natural gas in intrastate commerce. The FERC establishes uniform ceiling prices for each of several categories of natural gas, and these prices apply to all sales on a nationwide basis.

Federal Power Commission – An agency of the government of the United States created by an Act of Congress, the Federal Water Power Act, in 1920. Originally charged with regulating the nation’s water resources, the FPC later assumed responsibility for regulating the electric power and natural gas industries that sell or transport electricity or gas for resale in interstate commerce. With respect to the gas industry, the general regulatory principles of the FPC were defined in the Natural Gas Act, as amended. In 1977, the FPC passed into history and the Department of Energy was created, incorporating the independent regulatory agency known as the Federal Energy Regulatory Commission.

Feed Points – Connections between gas feeder lines and distribution networks.

Feeder (Main) – A gas main or supply line that delivers gas from a city gate station or other source of supply to the distribution networks.

Fin – A metal projection (of various design configurations) from the exterior surface of tubes in heat exchange equipment to increase the heat transfer area.

Fin Fan Cooler – A dry cooler that passes cooling air over finned tubes, through which some hot fluid is being passed, during the cooling process. A fan is used to create movement of air over the finned tubes. Air movement is regulated in a number of ways, the most common being a variable speed fan.

Fire Brick – Heat resistant refractory ceramic material formed into bricks and used to line fire boxes of boilers, furnaces, or other combustion chambers.

Fire Point – Minimum temperature at which a substance will continue to burn after being ignited.

Firing Rate – Therate at which fuel is fed to a burner, expressed as volume, heat units, or weightper unit time.

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Flame Test – Detectionand identification of certain elements in gas by characteristic colorationimparted to a flame.

Flame Velocity – The speed at which flame progresses through a fuel-air mixture.

Flash Back – The burning of gas in the mixing chamber of a burner or in a piping system, usually due to an excess of primary air or too low a velocity of the combustible mixture through the burner part.

Flow Formulas – In the gas industry, formulas used to determine gas flow rates or pressure drops in pipelines, regulators, valves, meters, etc.

Flue – Passage for combustion products within furnace or boiler.

Flue Collar – Thatportion of an appliance designed for the attachment of the draft hood or vent connector.

Flue Exhauster – Adevice installed in and made a part of the vent to provide a positive, induced, or balanced draft.

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Fuel Cell – System in which hydrogen is chemically reacted with oxygen to produce electricity.

Fuel Gas – A quantity of gas required by a transporter to provide the transportation service. Fuel gas includes, but is not limited to, gas consumed intransporter’s mainline compressor stations,gathering system booster stations and processing plants.

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Furnace – When used in a central heating system, this is a self-contained appliance for heating air by transfer of heat of combustion through metal to the air.

Furnace (Condensing) – Furnaces which recirculate the products of combustion and extract available heat to a point that causes condensation to occur. Some of this latent heat of vaporization is recovered as usable energy and results in higher operating efficiencies.

Furnace, Downflow – A forced-air type central furnace designed with air flow through the furnace essentially in a vertical path, discharging air at or near the bottom of the furnace.

Furnace, Duct – A central furnace designed for installation in a duct of an air distributionsystem to supply warm air for heating and which depends for air circulation on a blower not furnished as part of the furnace.

Furnace, Forced-Air – A central furnace equipped with a fan or blower which provides the primary means for circulation of air.

Furnace, Horizontal – A forced-air type central furnace designed with air flow through the furnace essentially in a horizontalpath.

Furnace, Upflow – A central furnace designed with air flow through the furnace essentially in a vertical path, discharging air at or near the top of the furnace.

Gas Absorption – The extraction of a gaseous substance from an atmosphere by liquid or solid material.

Gas Central Furnace and Boiler Efficiency Measures – The annual efficiency ratings of furnaces and boilers based on average usage, including on and off cycling as determined by standardized Department of Energy test procedures.

Gas Research Institute (GRI) – An organization sponsored by a number of U.S. gas companies to investigate new sources of supply and new uses (applications) for natural gas.

Gas Turbine – A prime mover in which gas, under pressure or formed by combustion, is directed against a series of turbine blades; the energy in the expanding gas is converted into mechanical energy supplying power at the shaft.

Gas, Flue – The products of combustion and excess air before the draft hood or draft regulator consisting principally of carbon dioxide, carbon monoxide, oxygen, and nitrogen.

Gas, Liquefied Petroleum (LPG) – A gas containing certain specific hydrocarbons which are gaseous under normal atmospheric conditions but can be liquefied under moderate pressure at normal temperatures. Propane and butane are the principal examples.

Gas, Manufactured – A gas obtained by destructive distillation of coal, or by the thermal decomposition of oil, or by the reaction of steam passing through a bedof heated coal or coke, or catalyst beds. Examples are coal gases, coke oven gases, producer gas, blast furnace gas, blue (water) gas, and carburetedwater gas. Btu content varies widely.

Gas, Natural – A naturally occurring mixture
of hydrocarbon and non-hydrocarbon gases found in porous geologic formationsbeneath the earth’s surface, often in association with petroleum. The principa constituent is methane. 1. Dry. Gas whose water content has been reduced by a dehydration process. Gas containing little or no hydrocarbons commercially recoverable as liquid product. Specified small quantities of liquids are permitted by varying statutory definitions in certain states. 2. Liquefied (LNG). 3. Sour. Gas found in its natural state, containing such amounts of compounds of sulfur as to make it impractical touse, without purifying, because of its corrosive effect on piping and equipment. 4. Sweet. Gas found in its natural state, containing such small amounts of compounds of sulfur that it can be used without purifying, with no deleterious effect on piping and equipment. 5. Wet. Wet natural gas is unprocessed natural gas or partially processed natural gas produced from strata containing condensable hydrocarbons. The term is subject to varying legaldefinitions as specified by certain state statutes. (The usual maximum allowable is 7lbs./MMcf water content and .02 gallons/Mcf of Natural Gasoline.)

Gas, Oil – A gas resulting from the thermal decomposition of petroleum oils, composed mainly of volatile hydrocarbons and hydrogen. The true heating value of oil gas may vary between 800 and 1600 Btu per cubic foot depending on operating conditions and feedstock properties.

Gas Pressure Booster – Gas pressure boosters are used for pumping low pressure gas up to the higher levels required by the downstream equipment. It is not a positive displacement pump such as would be used in gas compression for supply distribution, but more closely resembles a blower. The discharge pressure is the total of the incoming gas supply pressure plus the booster added pressure. (Inlet pressure plus boost pressure equals the outlet pressure.) Gas supplied through small piping will lose pressure as the flow increases. However as the gas appliance increases its firing rate, it will require more pressure than available, thus limiting its performance. A gas booster recovers the pressure deficit to allow full capacity operation.

Gas, Synthesis – A mixture of CO and H2 containing small amounts of nitrogen, some carbon dioxide and various trace impurities prepared for petrochemical synthesizing processes.It is also used in the manufacturing of SNG.

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Gas, Unconventional – Gas that cannot be economically produced using current technology.

Gas, Vent – Products of combustion from gas appliances plus excess air plus dilution air in the gasvent or chimney above the draft hood or draft regulator.

Gas-Oil Ratio – The quantity of gas produced with oil from an oil well, usually expressed as the number of cubic feet of gas produced per barrel of oil produced.

Gasification – The conversion of carbonaceous material into gas or the extraction of gas from another fuel.

Gasification – The process during which liquefied natural gas (LNG) is returned to its vapor or gaseous state through an increase in temperature and a decrease in pressure.

Gauge, Pressure – Instrument for measuring the relative pressure of a fluid. Types include gauge, absolute, and differential.

Generation, Non-Utility – Generation by producers having generating plants for the purpose of supplying electric power required in the conduct of their industrial and commercial operations. Generation by mining, manufacturing, and commercial establishments and by stationary plants of railroads and railways for active power is included.

Gas-oil ratio (GOR) – Generally, in the U.S., the volume of natural gas produced in cubic feet per barrel of oil produced.

Grid – The layout of a gas distribution system in which pipes are laid in both directions in the streets and frequently connected at intersections. Also, a series of equally spaced parallel bars held together by equally spaced crosspieces; a screen.

Head – The differential or pressure, usually expressed in terms of the height of a liquid column that the pressure will support. Also, the differential across a primary measuring device in feet of flowing fluid.

Headstation – A point at which gas enters the pipeline’s main transmission line, either at the interconnection of the gathering system or of a third party transporter. See POOLING POINT.

Heat Balance – The accounting of the energy output and losses from a system to equal the energy input.

Heat Capacity – Quantity of heat required to raise the temperature of a unit quantity of a substance onedegree. Interchangeable with “specific heat” in common usage.

Heat Exchanger, Direct – A heat exchanger in which heat generated in the combustion chamber of the device is transferred directly through walls of the heat exchanger to the heating medium such as air, steam, or water, held in close contact with the combustion-chamber walls. It is a self-contained combustion and heat-transfer device, hence a direct eat-transfer device.

Heat Exchanger, Indirect – A heat exchanger which encloses or contains a heating medium such as air, steam, or water, the heat from which is transferred to another heating medium separately contained in close contact with or directed through the heat exchanger. It is an indirect heat-transfer device.

Heat Gain – The amount of heat gained by a space from all sources, including people, lights,machines, sunshine, etc.

Heat Joining – Making a pipe joint by heating the mating surfaces of the parts to be joined so that they fuse and become essentially one piece with or without addition of material. NOTE: Also known as Heat fusion and Fusion.

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Heat Liberation Rate – The amount of heat which is liberated per unit time per cubic foot of combustion space.

Heat Loss – The sum cooling effect of a building structure when the outdoor temperature is lower than the desired indoor temperature.

Heat Pump – A year-round air-conditioning system employing refrigeration equipment in a manner which enables usable heat to be supplied to a space during the winter period, and by reversing the operation cycle to extract heat from the same space during the summer period. When operating as a heating system, heat is absorbed from an outside medium (either air, water, or the earth) and thisheat, together with the heat equivalent of the work of compression, is supplied
to space to be heated. When operating on the cooling cycle, heat is absorbed the work of compression, is rejected to the outside medium.

Heat Transfer – Flow of heatby radiation, convection, or conduction. This term is sometimes used to mean rate of heat transfer.

Heat Transfer Coefficient – The quantity of heat transferred through a unit area of a material in a unit time per unit oftemperature difference between the two sides of the material.

Heat, Latent – Change in heat content of a substance when its physical state is changed without a change in temperature; i.e., boiling or melting.

Heat, Sensible – That heat which, when added or subtracted, results in a change of temperature, as distinguished from latent heat.

Heat, Specific – The heat required to raise a unit mass of a substance through a degree oftemperature difference. Also, the ratio of the thermal capacity of a substance to that of water at 60 degrees F (15.6 degrees C). Interchangeable with “heat capacity” in common usage.

Heater, Construction – A self-contained, unvented, portable heater intended for temporary use during construction, sometimescalled a salamander.

Heater, Infra-Red Radiant (IR) – A self-contained, vented, or unvented heater used to convert the combustion energy to radiant energy, a substantial portion of which is in the infra-red spectrum, for the purpose of direct heat transfer.

Heater, Make Up Air – A self-contained, vented, or unvented, gas-fired air heater used only to heat air from the outside to replace air which is leaking, being vented, or being discharged from a heated building. May be direct-fired or indirect-fired.

Heater, Room – A self-contained, free-standing, non-recessed (except as noted below), gas-burning, air heating appliance intended for installation in the space being heated and not intended for duct connection. This shall not include heating appliances covered by other American Standard Approval or Listing It may be of either the gravity or mechanical air circulation type, vented, or unvented. (In some areas, this is referred to as a space heater).

Heater, Space – See Heater, Room

Heater, Unit – High static pressure type is a self-contained, automatically controlled, vented, gas-burning appliance, limited to the heating of nonresidential space.

Heater, Vented Recessed – A self-contained, vented appliance complete with grilles or equivalent, designed for incorporation in or
permanent attachment to a wall, floor, ceiling, or partition, and furnishing heated air circulated by gravity or by a fan directly into the space to be heated, through openings in the casing. Such appliances shall not be provided with duct extensions beyond the vertical and horizontal limits of the casing proper, except that boots not to exceed 10 inches beyond the horizontal limits of the casing for extension through walls of nominal thickness may be permitted. Where such boots are provided, they shall be supplied by the manufacturer as an integral part of the appliance and tested as such. This definition shall exclude floor furnaces, unit heaters, and central furnaces.

Heating Seasonal Performance Factor (HSPF) – HSPF is an abbreviation for Heating Seasonal Performance Factor. It is the mostcommonly used measure of the heating efficiency of heat pumps. (The cooling efficiency of a heat pump is measured by its SEER.) Technically speaking, the HSPF is a heat pump’s estimated seasonal heating output in divided by the amount of energy that it consumes.

Heating System, High-Pressure Steam – A steam heating system employing steam at pressure above 15 psig.

Heating System, High-Temperature Water – A heating system in which water having supply temperature above 350 degrees Fahrenheit is used as a medium to convey heat from a central boiler, through a piping system, to the heating units.

Heating System, Hot Water – A heating system in which water having supply temperatures less than 250 degrees Fahrenheit is used as medium to convey heat from a central boiler, through a piping system, to the heating units.

Heating System, Low-Pressure Steam – A steam heating system employing steam at pressures below 15 psig.

Heating System, Medium-Temperature Water – A heating system in which water having supply temperatures between 250 and 350 degrees Fahrenheit is used as a medium to convey heat from a central boiler, through a piping system, to the heating units.

Heating System, Steam – A heating system in which heat is transferred from a boiler or other source to the heating units by means ofsteam.

Heating Value – The amount of heat produced by the complete combustion of a unit quantity of fuel.The gross of higher heating value is that which is obtained when all of the products of combustion are cooled to the temperature existing before combustion, the water vapor formed during combustion is condensed, and all the necessary corrections have been made. The net or lower heating value is obtained by subtracting the latent heat of vaporization of the water vapor, formed by the combustion of the hydrogen in the fuel, from the gross or higher heating value.

High Btu Gas – A term used to designate fuel gases having heating values of pipeline specification, i.e., greater than about 900 Btus per standard cubic foot.

High Heat Value – The gross or high heating value is the amount of heat produced by the complete combustion of a unit quantity of fuel. The gross heating value is obtained when:

all products of the combustion are cooled down to the
temperature before the combustion
the water vapor formed during combustion is condensed

High Btu Oil-Gas Process – A manufactured gas process in which oil is converted into a fuel gas having a higher heating value than that of coal gas or carbureted water gas. Often called Hi-Btu Gas Process.

Horsepower, Boiler – A boiler horsepower is used for boilers in power plants. It is equal to 33,475 Btu/h (9.8095 kW), which is the energy rate needed to evaporate 34.5 lb (15.65 kg) of water at 212 °F (100 °C) in one hour.

Horsepower, Brake – Brake horsepower (abbreviated bhp) is the measure of an engine’s horsepower without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliary components such as alternator,power steering pump, muffled exhaust system, etc.

Hourly Peak – The maximum demand for gas from a transmission or distribution system in a one hour period of time.

Humidifier – A mechanical means of increasing the relative humidity by injecting water or water vapor into the air.

Humidistat – A regulating device, actuated by changes in humidity, used for the automatic control of relative humidity.

Humidity – The entrained weight of water per unit weight of moisture-free gas or air.

Humidity, Relative – The ratio of the weight of water vapor in the atmosphere to the weight the air would hold if completely saturated at that temperature, expressed as a percentage.

Heating Ventilation and Air Conditioning System (HVAC) – A system that provides either collectively or individually the processes of comfort heating, ventilation and/or cooling within or associated with a building.

Hydrate – A solid ice-like material resulting from the combination of a gas with water under pressure. Of naturalgas constituents — methane, ethane, propane, isobutane, normal butane, andalso hydrogen sulfide and carbon dioxide will form hydrates. The greater the pressure in the equipment, the higher the temperature at which the hydrate will form, usually well above freezing. Hydrates can cause restriction or stoppage of flow, and can be controlled by alcohol injection or by dehydration of the gas. Methane hydrates are found in some permafrost regions and beneath portions
of the ocean floor and may eventually be a source of methane gas.

Hydrocarbon – A chemical compound composed solely of carbon and hydrogen. The compounds having
a small number of carbon and hydrogen atoms in their molecules are usually gaseous; those with a larger number of atoms are liquid, and the compounds with the largest number of atoms are solid.

Hydrogen (H2) – A colorless, odorless, highly flammable gas used in hydrogenation of petroleum and for producing ammonia. Also, an important constituent of manufactured gas.

Hydrogen Sulfide (H2S) – A poisonous, corrosive compound consisting of two atoms of hydrogen and one of sulfur, gaseous in its natural state. It is found in manufactured gas made from coals or oils containing sulphur and must be removed. It is also found to some extent in some natural gas. It is characterized by the odor of rotten eggs.

Hydronics – Heatingand/or cooling with circulated water.

Hygrometer – An instrument for determining the relative humidity of air or other gases.

Ignition Temperature – The temperature at which a substance, such as gas, will ignite and continue burning with adequate air supply.

Ignition, Automatic – A means which provides for automatic lighting of gas at the burner when the gas valve controlling flow is turned on and will effect relighting if the flame on the burner has been extinguished by means other than closing the gas burner valve.

Ignition, Continuous – Ignition by an energy source which is continuously maintained through the time the burner is in service, whether the main burner is firing or not.

Ignition, Intermittent – Ignition by an energy source which is continuously maintained through the time the burner is firing.

Ignition, Interrupted – Ignition by an energy source which is automatically energized each time the main burner is fired and subsequently is automatically shut off during the firing cycle.

Ignition, Manual – Ignition by an energy source which is manually energized and where the fuel to the pilot is lighted automatically when the ignition system is energized.

Inch Water Column – Unit of measure for pressure. 1 PSIG – 27._ Inch w.c.

Incremental Cost – The additional costs incurred from the production or delivery of an additional number of units of gas, usually the minimum capacity or production that can be added. The additional cost divided by the additional capacity or output is defined as the incremental cost. Also, in DSM (demand side management), the difference in costs between an efficient technology or measure and the alternative standard technology.

Independent Petroleum Association of America (IPAA) – A trade group representing independent oil and gas producers.

Independent Power Producer (IPP) – Wholesale electric producerunaffiliated with the franchised utility in the area in which it is selling power.

Independent System Operator (ISO) – An organization formed at the direction orrecommendation of the Federa Energy Regulatory Commission (FERC). In the areas where an ISO is established, it coordinates controls and monitors the operation of the electrical power system, usually within a single US State, but sometimes encompassing multiple states.

Similar to an ISO is a Regional Transmission Operator (RTO), the primary difference being that generally an RTO coordinates controls and monitors the operation of the electric power transmission system over a wider area that crosses state borders.

Only electric utilities that are located within the United States fall under FERC authority, but a larger organization called the North American Electric Reliability Corporation (NERC)overlays the entire FERC footprint and also includes a Mexican utility and several Canadian utilities. As such, international reciprocityi commonplace, and rules or recommendations introduced by FERC often are oluntarily accepted by NERC members outside of FERC’s jurisdiction. Therefore, one Canadian Province is a member of a US-based RTO, while two others function as an Electric System Operator (ESO), an organization essentially equal to aUS-based ISO.

Indirect Oven Thermostat System – A control system of two or more integrated automatic devices to maintain a selected oven temperature. That portion of the system responsive to oven temperature causes operation of another portion of the system to turn on or shut off the gas supply to the oven burner.

Indirect-Fired – A heater in which combustion products do not come in contact with the material to be heated; heating of the material is accomplished by radiation or conduction from the heated surfaced.

Indoor Air Quality (IAQ) – Deals with the content of interior air that could affect health and comfort of building occupants. The IAQ may be compromised by microbialcontaminants (mold, bacteria), chemicals (such as carbon monoxide, radon), allergens, or any mass or energy stressor
that can induce health effects. Using ventilation to dilute contaminants, filtration, and source control are the primary methodsfor improving indoor air quality in most buildings. <![if !supportLineBreakNewLine]> <![endif]>

Techniques for analyzing IAQ include collection of air samples, collection of samples on building surfaces and computer modeling of air flow inside buildings.The resulting samples can be analyzed for mold, bacteria, chemicals or otherstressors. These investigations can lead to an understanding of the sources of the contaminants and ultimately to strategies for removing the unwanted elements from the air.

Infiltration – The air entering a space through a wall, crack, doors, and other openings.

Input Rate – The rate at which gas is supplied to an appliance. It may be expressed in Btu per hour (Btuh), thousands of Btu per hour (MBtuh); in cubic feet perhour (cfh); or thousands of cubic feet per hour (Mcfh); in therms (th) or dekatherms (Dth) per hour.

Input Rating – The gas-burning capacity of an appliance in Btu per hour as specified by the manufacturer. Appliance input ratings are based on sea level operation and need not be changed for operation up to 2,000 feet.

Integrated Resource Planning – A utility planning method whereby alternative resource mixes, including demand-side and supply-side options, are evaluated in order to determine which resource plan minimizes.

Integrating Pressure-and-Temperature Instrument – The integratingpressure-and-temperature instrument registers, on a counter, the total quantityof gas passed through the meter, reduced to standard cubic feet at a definitebase pressure and base temperature. Each increment of volume is multiplied by a temperature-factor corresponding to the line-temperature and base-temperature. It is then multiplied by the pressure-multiplier corresponding to the line
pressure and base pressure. The product is totaled on a counter index. A supplementary index is furnished which reads the total quantity passed at line
conditions.

Integrating Pressure-Instrument – The integrating pressure-instrument registers the total volume of gas metered in cubic feet at a specified base pressure. This instrument is equipped with a second register which records the total volume at the flowing pressure. Each unit of volume flowing through the meter causes the integrating mechanism to make one cycle and apply the correct pressure multiplier for that unit. The summation of these products is registered on a counter index indicating the displaced volume at base pressure.

Interior Zones – The portions of a building which do not have significant amounts of exterior surfaces. Such zones have heating or cooling needs largely dependent upon internal factors such as lighting.

Internal Combustion – Pertains to any engine in which the heat or pressure necessary to produce power is developed in the engine cylinder by the combustion of a fuel.

Internal rate of Return (IRR) – It is an indicator of the efficiency or quality of an investment, as opposed to net present value (NPV), which indicates value or magnitude. The IRR is the annualized effective compounded return rate which can be earned on the invested capital, i.e., the yield on the investment.

A project is a good investment proposition if its IRR is greater than the rate of return that could be earned by alternate investments.

In general, if the IRR is greater than the project’s cost of capital, or hurdle rate, the project will add value for the company.

Interruptible Service – Low priority service offered to customers under schedules or contracts which anticipate and permit interruption on short notice, generally in peak-load seasons, by reason of the claim of firm service customers and higher priority users. Gas is available at any time of the year if the supply is sufficient and the supply system is adequate.

Interruptible Transportation Service (ITS) – Low priority service offered to customers under schedules or contracts which anticipate and permit interruption on short notice, generally in peak-load seasons, by reason of the claim of firm service customers and higher priority users.

Interstate – With respect to natural gas companies, the transporting and sale of gas for resale across state lines.

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Interstate Gas – Gas transported in interstate pipelines to be sold and consumed in states other than that state in which the gas was produced.

Kilowatt (KW) – A unit of electrical work equivalent to 1,000 watts, 1.3414 horsepower, or .9478 Btu/sec. It is also the demand component on an electric bill.

Kinetic Energy – Energy possessed by a body due to its own motion.

Leak Detector – Adevice for identifying and locating a gas leak.

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LEED Rating System – The Leadership in Energy and Environmental Design (LEED) Green Building Rating System™ is a third-party certification program and the nationally accepted benchmark for the design, construction and operation of high performance green buildings. LEED gives building owners and operators the tools they need to have an immediate and measurable impact on their buildings’ performance. LEED promotes a whole-building approach to sustainability by recognizing performance in five key areas of human and environmental health: sustainable site development, water savings, energy efficiency, materials selection and indoor environmental quality.

Life Cycle Cost –Refers to the investigation and valuation of the environmental impacts of a given product or service caused or necessitated by its existence.

Liquefaction of Gases – Any process in which gas is converted from the gaseous to the liquid phase.

Liquefied Natural Gas (LNG) – Natural gas which has beenliquefied by reducing its temperature to minus 260 degrees Fahrenheit at atmospheric pressure. It remains a liquid at -116 degrees Fahrenheit and 673 psig. In volume, it occupies 1/600 of that of the vapor at standard conditions.

Liquefied Petroleum Gas (LPG) – A gas containing certain specific hydrocarbons which are gaseous under normal atmospheric conditions, but can be liquefied under moderate pressure at normal temperatures. Propane and butane are the principal examples.

Load – The amount of gas delivered or required at any specified point or points on a system; load originates primarily at the gas consuming equipment of the customers. Also, to load a pressure regulator is to set the regulator to maintain a given pressure as the rate of gas flow through the regulator varies.

Load Center – A point at which the load of a given area is assumed to be concentrated.

Load Curve – A graph in which the load of a gas system or segment of a system is plotted against intervals of time.

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Load Density – The concentration of gas load for a given area expressed as gas volume per unit of time and per unit of area.

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Load Diversity – The difference between the sum of the peaks of two or more individual loads and thepeak of the combined load. See DIVERSITY FACTOR.

Load Duration Curve – A graph made by plotting datain order of magnitude against time intervals for a specified period. The ordinate may be an absolute quantity or percentage.

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Load Factor – The ratio of the average energy requirement to the maximum requirements for thesame time period, as one day, one hour, etc. Typically used to rate electric consumption to demand.

Load Shedding – The use of natural gas fired electric generators tooffset electric load.

Load Profile – Pattern of a customer’s gas usage, hour to hour, day to day, or month to month.

Load Research – The systematic gathering, recording, and analyzing of data describing customers’patterns of energy usage.

Louvers – Overlapping and sloping slats arranged to prevent entrance or exit of some substances but allow ventilationair to pass.

Low Btu Gas – Gaswith a heating value of less than 250 Btu’s per cubic foot. Typically heating values fall between 120 and 180 Btu’s per cubic foot.

Low Heat Value – The net or lower heating value is obtained by subtracting the latent heat of vaporization of the water vapor formed by the combustion from the gross or higher heating value.

Mains, Gas – Pipes used to carry gas from one point to another. As contrasted with service pipes, they carry gas in large volume for general or collective use.

Manifold – The conduit of an appliance which supplies gas to the individual burners. Also, a pipe to which two or more outlet pipes are connected.

Mantle – A lace-like hood or envelope (sack) of some refractory material which, when placed in position over a flame, gives light by incandescence.

Manufactured Gas – A gas obtained by destructive distillation of coal, by the thermal decomposition of oil, or by the reaction of steam passing through a bed of heated coal orcoke. Examples are coal gases, coke or oven gases, producer gas, blast furnace gas, blue (water) gas, or carbureted water gas. The Btu content varies widely.

Market Potential – InDSM (demand side management), an estimate of the possible energy savings that would occur because of normal market forces, without the implementation of a DSM (demand side management) program.

Market-Based Pricing – The basing of a longer-term contract or rate schedule on published current market prices of competing supplies of natural gas or alternate fuels.

Mcf – The quantity of natural gas occupying a volume of one thousand cubic feet at atemperature of sixty degrees Fahrenheit and at a pressure of fourteen and seventy-three hundredths pounds per square inch absolute.

Maximum Daily Quantity (MDQ) – The term MDQ refers to maximum daily quantity of gas which a buyer, seller, or transporter is obligated to receive or deliver at each receipt or delivery point or in the aggregate as specified in an agreement.

Measuring and Regulating Station – Facilities installed at a given location for measuring and regulating the flow of gas in connection with distribution system operations other than the measurement of gas deliveries to customers.

Mechanical Equivalent of Heat – The conversion factor for transforming heat units into mechanical units of work. One Btu equals 778 foot-pounds.

Meter Density – The number of meters per unit of area or per unit length of distribution main.

Meter Index (Meter Register) – That part of a meter which indicates the volume of gas passed through the meter.

Meter Manifold – Gas piping between gas service line and meter. Also, gas piping supplying two or more meters.

Meter Seal – A metal wire or tape seal attached to a gas meter or a service stop in such a way as to prevent its being opened by an unauthorized person.

Meter Set (Meter Installation) – The meter and appurtenances thereto, including the meter, meter bar, and connected pipe and fittings. Also called METER SET ASSEMBLY.

Meter Stop – A shut-off valve located on the inlet side of the meter. It may be integral with the meter bar.

Meter Swivel – The fitting that connects to the inlet and the outlet of a small gas meter.

Meter, Gas – An instrument for measuring and indicating or recording the volume of gas that has passed through it.

Meter, Rotary (gas meter) – A gas meter is used to measure the volumeof fuel gases such as natural gas and propane. Gas meters are used at residential, commercial, and industrial buildings that consume fuel gas supplied by a gas utility. Gases are more difficult to measure than liquids, as measured volumes are highly affected by temperature and pressure. Gas meters measure a defined volume,regardless of the pressurized quantity or quality of the gas flowing through the meter. Temperature, pressure and heating value compensation must be made to measure actual amount and value of gas moving through a meter.

Meter, Turbine – A velocity measuring device in which the flow is parallel to the rotor axis andthe speed of rotation is proportional to the rate of flow. The volum of gas measured is determined by the revolutions of the rotor and converting them to a continuously totalized volumetric reading.

Methane (CH4) – The first of the paraffin series of hydrocarbons. The chief constituent of natural gas. Pure methane has a heating value of 1012 Btu per cubic foot.

Mixed Gas – Fuel gas in which natural or LP gas is mixed with manufactured gas.

Mixture, Rich – A gas-air mixture of which the air content is not sufficient for complete combustion.

MMBtu – A thermal unit of energy equal to 1,000,000 Btus, that is, the equivalent of1,000 cubic feet of gas having a heating content of 1,000 Btus per cubic foot, as provided by contract measurement terms.

MMcf – A million cubic feet.

Modified Btu Method – A modification of the Btu Method of allocating costs between different operations or between different products.

Modified Fixed-Variable (MFV) Method – A method for classifying fixed costs among demand and commodity charges in which all fixed costs except return on equity capital and related income tax items are classified to the demand charge. This method generally replaced other methods used by the Commission for classifying demand costs when first approved in the mid-1980s. The MFV method of cost classification usually is accompanied with a rate design methodology which employs a two-part (D-1 and D-2) demand and a commodity rate structure.

Monitor – To sense the presence of a flame. The device which does this is called a flame monitor. Also, to analyze and record various desired and undesired components of an atmosphere, or stream of flowing gas or fluid.

Monitoring Regulator – A pressure regulator set in series with a control pressure regulator for the purpose of automatically taking over the control of the pressure downstream in case that pressure tends to exceed a set maximum.

Name PlateRating – The full-load continuous rating of a generator, prime mover, pump, compressor, or other equipment under specified conditions as designated by the manufacturer. It is usually indicated on a name plate attached mechanically to the individualmachine or device.

National Association of Regulatory Utility Commission – A voluntary organization composed of federal and state regulatory commissioners who have jurisdiction over transportation agencies and public utilities.

National Fuel Gas Code – A code that provides general criteria for the installation and operation of gas piping and gas equipment on consumers’ premises. The code is sponsored by both the National Fire Protection Association (NFPA-54) and the American National Standards Institute (ANSI Z223.1).

National Gas Transportation Association (NGTA) – Formerly the National Transportation & Exchange Association. A group that promotes understanding of the national pipeline grid and is working toward standardization in the industry.

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Natural Gas Liquids – The hydrocarbon components: propane, butanes, and pentanes (also referred to as condensate), or a combination of them that are subject to recovery from raw gas liquids by processing in field separators, scrubbers, gas processing and reprocessing plants, or cycling plants. The propane and butane components are often referred to as liquefied petroleum gases or LPG.

Natural Gas Supply Association (NGSA) – A trade group representing major integrated gas producers, medium-sized companies and independents.

Natural Gas Vehicle (NGV) – A vehicle that is equipped to operate using natural gas, either as the sole fuel (a dedicated NGV) or as an option(a dual-fuel NGV).

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Natural Gasoline – Liquidremoved from natural gas by absorption or refrigeration and containing hydrocarbons heavier than butane.

Network – Asystem of transmission or distribution lines cross-connected and operated as to permit multiple supply to any principal point on it.

New Construction Program – A DSM (demand side management) program that affects the design and construction of new buildings and facilities.

New Gas – Gasproduced from wells drilled on production leases acquired on or after February 19, 1977.

Nitrogen (N2) – Anodorless, colorless, generally inert gas. It comprises 79% of the earth’s atmosphere in the free state.

Non-Hydrocarbon Gases – Typical non-hydrocarbon gases which may be present in natural gas are carbon dioxide, nitrogen, hydrogen sulfide, and helium.

Noncombustible – A substance or gas that will not burn.

Normal Recovery Capacity – Amount of water in U.S. gallons raised 100 degrees F per hour or per minute when calculated on a thermal efficiency of 70%, representing the water heated by a gas input of 1,190 Btu per gallon.

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Normal Test Pressures – Those pressures specified fortesting purposes at which adjustment of burner ratings and primary adjustments are made.

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Odorant – Any material added to natural or LP gas in small concentrations to impart a distinctive odor. Odorants in common use include various mercaptans, organic sulfides, and blends of these.

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Off-Peak – Theperiod during a day, week, month, or year when the load being delivered by a gas system is not at or near the maximum volume delivered by that system for the corresponding period of time.

Oil, Heavy – Heavy, thick, and viscous oils. Usually refinery residuals commonly specified as grades 5 and 6.

Oil, Light – Generally, all oils lighter than residual fuel oil No. 5 and No. 6. Oils that have a lowspecific gravity, usually products of controlled distillation of crude oil but also including by-product benzol and toluol.

Oil, Live – Anoil containing dissolved gas.

Oil, White – The term given to natural gas liquids produced from refrigeration units at the well site.

Old Gas – Gas produced from wells as a result of well work over or stimulation of existing production wells on leases acquired prior to February 19, 1977.

On-Site Generation – Generation of any electrical energy on a customer’s property, with or without utilizationof recoverable heat.

Open-Flow Test – A test made to determine the volume of gas that will flow from a well in a given time when flowing unrestricted and open to the atmosphere.This is usually calculated from pressure tests of restricted flow.

Optimum Air Supply – Volume ofair delivered to a burner that will produce the maximum thermal efficiency under specific operating conditions.

Oven, Indirect – One in which the flue gases do not flow through the oven compartment.

Oxygen (O2) – A gas which forms about 21%, by volume, of the atmosphere. It is chemically very active and is necessary for combustion. The combination of oxygen with other substances generally produces heat.

Oxygen Deficiency – An atmosphere containing oxygen at a concentration of less than 19.5% by volume and is not safe for breathing.

Payback Period – The time required for the cumulative operational saving of a DSM (demand side management) (or other) option to equal the investment cost of that option.

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Peak Day – The one day (24 hours) of maximum system deliveries of gas during a year. Peak day data is used to, among other things; determine the allocation of certain costs between classes of service. The Commission sometimes required allocation based on an average of three continuous days of maximum deliveries (i.e., three day peak).

Peak Demand – Refers to the maximum electric demand drawn in some short interval of time, typically 15 minutes or 30 minutes.

Peak Hour – The one-hour period of greatest total gas send out or use.

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Peak Load – The maximum load consumed or produced by a unit or group of units in a stated period of time.

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Peak Responsibility – The load of a customer, a group of customers, or part of a system at the time of occurrence of the systempeak.

Peak Shaving -Generating electric power to reduce peak electric demands that occur over the course of the day or month. (a better def. probably exists)

Persistence – A measure of the effectiveness, over time, of a DSM (demand side management) measure, usually represented by the percentage of energy savings that remainseach year. A decline in the energy savings of DSM (demand side management) options is usually caused by the following two factors: equipment degradation and consumer behavior.

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Petroleum – An oil, flammable bituminous liquid that may vary from almost colorless to black, occurs in many places in the upper strata of the earth; is a complex mixture of hydrocarbons with small amounts of other substances, and is prepared for use as gasoline, naphtha, or other products by various refining processes.

Pilot – Asmall flame which is utilized to ignite the gas at the main burner(s).

Pilot Program – ADSM (demand side management) program that is generally limited in scope or targeted to a select group of customers and is designed to test or build capability to deliver a full scale program.

Pilot, Continuous – A pilot that burns without turn-down throughout the entire time the burner assembly is in service, whether the main burner is firing or not.

Pilot, Expanding – A pilot that burns throughout the entire time the burner assembly is in service, whether the main burner is firing or not. Upon a call for heat, the pilot is automatically expanded so as to reliably ignite the main burner. This pilot may be turned down automatically at the end of main burner flame-establishing period.

Pilot, Intermittent – A pilot which is automatically lighted each time there is a call for heat, it burns during theentire period that the main burner is firing.

Pilot, Interrupted – Apilot which is automatically lighted each time there is a call for heat. The pilot fuel is cut off automatically at the end of the main burner lame-establishing period.

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Pipeline – All parts of those physical facilities through which gas is moved in transportation, including pipe, valves, and other appurtenances attached to pipe, compressor units, metering stations, regulator stations, delivery stations, holders, and fabricated assemblies.

Pollution, Atmospheric – Degradation of atmospheric quality due to heat, particulate, or other products from industrial plants, power plants, refineries, or vehicular engines.

Port – Opening in the seat of a slide valve in diaphragm gas meters or an opening in any equipment for the flow of gases or vapors.

Potential – A measure of the capacity of a well to produce oil or gas. When a well is completed, its productive capacity is determined by an official test. The capacity as shown by this test is known as the well’s potential. The allowablerate of production assigned to the well is based in whole or in part on its potential.

Potential Energy – Stored energy or energy possessing the power of doing work but not actually performing such work.

Power Combustion Furnaces – Furnaces that have a combustion blower, which may be located either upstream or downstream from the heat exchangers. If the blower is located upstream, blowing the combustion air into the heat exchangers, the system is called a forced-draft system. If the blower is downstream, the arrangement is called an induced-draft system. Power combustion systems have been commonly used with outdoor furnaces in the past;however, more indoor furnaces are being designed using this concept.

Pressure Control – Maintenance of pressure, in all or part of a system, at a predetermined level or within a selected range.

Pressure, Differential – Difference in pressure between any two points in a continuous system.

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Pressure Drop – The loss in static pressure of the fluid (air, gas, or water) due to friction or obstruction in pipe, valves, fittings, regulators, burners, appliances, and breeching.

Pressure Losses – Lossesin static or velocity pressure in a piping system due to friction, eddies, leaks, or improper piping design.

Pressure Rating – The estimated maximum pressure that the medium in the pipe can exert continuously with a high degree of certainty that failure of the pipe will not occur.

Pressure Regulating Station – Equipment installed for the purpose of automatically reducing and regulating the pressure in the downstreampipeline or main to which it is connected. Included are piping auxiliary devices such as valves, control instruments, control lines, the enclosures, and ventilating equipment.

Pressure, Absolute (PSIA) – Pressure in excess of aperfect vacuum. Absolute pressure is obtained by algebraically adding gauge pressure to atmosphere pressure. Pressures reported in “Atmospheres” are understood to be absolute. Absolute pressure must be used in equations of state and in all gas-law calculations. Gauge pressures below atmosphericpressure are called “vacuum.”

Pressure, Atmospheric – The pressure due to the weight of the atmosphere (air and water vapor) on the earth’s surface. Theaverage atmospheric pressure at sea level (for scientific purposes) has been defined at 14.696 pounds per square inch absolute.

Pressure, Critical – The minimum pressure required to liquefy a gas at its critical temperature.

Pressure, Gauge (PSIG) – Pounds per square inch above atmospheric pressure.

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Pressure, Maximum Actual Operating – The maximum pressure that occurs during normal operations over a one-year period.

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Pressure, Maximum Allowable Operating – The maximum operating pressure at which a system or a device may be operated as determined by regulating codes.

Pressure, Suction – The inlet pressure to a compressor, pump, or fan.

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Pressure, Total – The sum of the static pressure and the pressure due to the velocity motion.

Pressure, Trap – Pressure held at the trap or oil and gas separator.

Pressure, Velocity – The pressure which would be exerted by a fluid due to its motion if brought to rest. This is distinguished from the static pressure exerted against walls containing the fluid.

Pressure, Working – Normal operating gauge pressure in a device or system.

Pressure-Decline – Curve Method – A method of estimating non-associated gas reserves in reservoirs which do not have a water drive.

Preventive Maintenance – Examination of plant and equipment on a schedule basis and the replacement or repair ofparts that are worn by prescribed amounts or that are in such condition that further use will involve the risk of their failure while in service. It is designed to prevent operating breakdown.

Primary Air – Air that is mixed with fuel before the mix reaches the ignition zone to enhance combustion.

Propane (C3H8) – A gas, the molecule of which is composed of three carbon and eight hydrogen atoms. Propane is present in most natural gas and is the first product refined from crude petroleum. It has many industrial uses and may be used for heatingand lighting. Contains approximately 2,500 Btu per cubic foot.

Propane Air Blender- Technology typically used to blend a air with propane to create a product with similar characteristics to natural gas.

Psi – Pounds per square inch.

Psychometric – Pertaining to the state of the atmosphere with reference to moisture.

Psychrometer – A device for measuring the humidity in the air, employing a wet bulb and a dry bulb thermometer.

Public Utility – A business organization performing a service relating to or affecting all of the people within a specified area, usually under provisions of a franchise, charter or “certificate”, and subject to special governmental regulations. See SERVICE AREA.

Purge – To displace gas, liquids, or foreign matter from piping, tanks, and equipment withother gases or liquids.

Purge Cycle – Asapplied to electric pilot igniters, the period from the time of automatic closure of the main gas supply by the safety shutoff device to the time the electrical circuit is re-energized.

Purging – The act of replacing the atmosphere within a container by an inert substance in such a manner as to preventthe formation of explosive mixtures.

Purification – Theprocess by which unwanted impurities, such as hydrogen sulfide, are removed from a gas mixture. Purification of gas is accomplished by two principal methods. The dry method in which the gas is passed through some purifying material such as iron oxide mixed with wood shavings, and the wet method in which the gas is brought in contact with some liquid containing an active purifying agent such as ethanolamine or arsenic trioxide.

Qualifying Facility (QF) – Qualifying facilities are a distinct class of energy producer which consists of either small-scale producers of commercial energy who normally self-generate energy for their own needs but may have occasional or frequent surplus energy, or incidental producers who happen to generate saleable electric energy as a byproduct of other activities. When a facility of this type meets the Federal Energy Regulatory Commission’s requirements for ownership, size and efficiency, utility companies are obliged to purchase energy from these facilities based ona pricing structure referred to as avoided cost rates. These rates tend to behighly favorable to the producer, and are intended to encourage more productio of this type of energy as a means of reducing emissions and dependence on other sources of energy.

Qualifying facilities were first classified in 1978 with the establishment of the Public Utility Regulatory Policies Act, a piece of legislation which was intended to encourage more efficient and environmentallyfriendly energy production in the United States.

R-Value – A measure of thermal resistance of a material, equal to the reciprocal of theU-Value. The R-Value is expressed in terms of degrees Fahrenheit times hours, times square feet per Btu.

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Radiator – A heating unit which transfers heat by radiation to objects within visible range and by conduction to the surrounding air which, in turn, is circulated by natural convection; a so-called radiator is also a convector, but the term radiator has been established by long usage.

Range, Gas – Cooking stove. GAMA lists the following types: (1) Free-standing; (2) Set-in; (3) High Oven; (4) Built-in, Commercial; (5) Luncheonette and Restaurant; (6) Heavy Duty (Quality, Battery Type).

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Ratchet Penalty – Term used to describe a cost premium for electric associated. A ratchet occurs when a customer is billed at a higher electric demand than registered.

Rate – Theunit charge or charges made to the customers for natural gas.

Rate of Flow – The volume or units of a material passing a given point in a system per unit oftime.

Rate of Return – The return allowed to be earned (generally based on a cost of capital determination) or earned by a utility enterprise, generally calculated by dividing the net operating income (as defined) by the rate base.

Rate Schedule, Cogeneration – A special rate to encouragecommercial and industrial customers to use gas-fired cogeneration (generates their own electricity and use the waste heat from this process for thermal requirements).

Rate Schedule, Economic Development – A discount from standard commercial and industrial rates for takes above a minimum level for new or expanded service within an existing service area.

Rate Schedule, Flat – A rate schedule which providesfor a fixed per unit charge regardless of the quantity of gas used.

Rate Schedule, Gas Cooling – A discount for using gas for air conditioning during the summer or off peak period.

Rate Schedule, Inverted – A rate schedule which provides different, but increasing, unit charges for various blocks of increasing demand or energy.

Rate Zones – Geographic areas of the Company’s operations established to facilitate a design of rates to properly reflect the cost of serving customers in different parts of the company’ssystem.

Rates, Meter – The term “meter rate” is applicable to any method of charge for gasservice based solely upon quantity, such as Mcf or therms used. The term “block” indicates that a certain specified price per unit is charged for all units of gas taken within specified increments of use. Reduced prices per unit are charged for all or any part of succeeding blocks of such units, each such reduced price per unit applying only to a particular block or portion thereof. The term “inverted” indicates that an increasing unit charge will be applied to succeeding blocks of increasing energy use. The term “step” indicates that a certain specified price per unit is charged for all gas taken during a billing period, the rate, or price depending on the particular step within which the total consumption falls. The term “straight-line” indicates that the price charged per unit is constant, i.e., does not vary on account of an increase or decrease in the number of units.

Ratio of Specific Heats – For gases: The ratio of thespecific heat at constant pressure to the specific heat at constant volume. This ratio is important in thermodynamic equations, and is given the symbol kwhere k=cp/cv. The ratio k lies between 1.2 and 1.4 for most gases.

Rebate Program – A DSM (demand side management) program in which the utility offers a financial incentive for the installation of energy-efficient equipment. Non-DSM (demand side management) rebate programs also exist, in which the utility offers an incentive for purposes of gaining market share of a specific end-use.

Recoverable Heat – That portion of thermal input to a prime mover that is not converted to mechanical power and can be reclaimed for utilization.

Recovery Capacity, Water Heater – The quantity of water that a water heating system can heat from supply temperature to required temperature in one hour.

Refrigerant – A substance which will absorb heat while vaporizing and whose boiling point and other properties make it useful as a medium for refrigeration. (Chilled water, which by common acceptance is called a refrigerant, does not vaporize).

Refrigerating System, Absorption – A system whereby a secondary fluid absorbs the refrigerant, and in doing so, gives up heat, subsequently releasing the refrigerant, during which heat is absorbed.

Refrigerating System, Vapor-Compression – A refrigerating system in which the cooling effect results from expansion of a refrigerant aftermechanical compression by either centrifugal or reciprocating compressors.

Refrigeration Capacity – The rate of heat removal by a refrigerating system, usually expressed in Btu per hour or in tons.

Refrigeration Cycle – The full sequence of condensation and evaporation. The heat of evaporation is obtained from the material to be cooled.

Refrigeration Ton – 12,000Btu per hour or 200 Btu per minute of heat removal. Originally, the amount of heat required to melt a ton of ice in 24 hours.

Regenerative Heating (Or Cooling) – Process of utilizing heat which must be rejected in one part of the cycle to perform a useful function in another part of the cycle.

Regulator, Domestic Appliance Pressure – A device either adjustable or non-adjustable for controlling and maintaining a uniform outlet gas pressure. Spring Type, Adjustable – A regulator in which the regulating force acting upon the diaphragm is derived principally from a spring, the loading of which is adjustable. Spring Type, Nonadjustable – A regulator in which the regulating force acting upon the diaphragm is derived principally from a spring, the loading of which is not adjustable. Either of the above types may be further classified as follows: Main Burner Load Application – A regulator capable of controlling the flow of gas to main burners only. In such applications, the pilot is taken off upstream from the regulator. Main Burner and Pilot Load Application – A regulator capable of controlling the flow of gas to main and pilot burners. In such applications the pilot is taken off downstream from the regulator valve.

Regulator, Monitoring – A pressure regulator set in series with a control pressure regulator for the purpose of automatically taking over, in an emergency, the control of the pressure downstream of the station in case that pressure tends to exceed a set maximum.

Regulator, Pressure – A device that maintains the pressure in a fluid flow line, less than its inlet pressure within a constant band of pressures, regardless of the rate of flow in the line or the change in upstream pressure.

Regulator, Relief Pressure – A device for the purpose of elieving pressures in excess of a predetermined pressure.

Regulator, Service Pressure – A device designed to reduce and limit the gas pressure at the customer’s meter.

Regulatory Adjustments – Company costs in the base period that cannot be included in the Cost of Service and are deleted.

Relief Opening – The opening provided in a draft hood to permit the ready escape to the atmosphere of the flue products from the draft hood in the event of no draft, back draft, or stoppage beyond the draft hood, and to permit inspiration of air into the draft hood in the event of a strong chimney updraft.

Reserves, Energy – Refers to the bank of natural resources, such as natural gas, natural gas liquids, petroleum, coal, lignite, energy available from water power, and solar and geothermal energy.

Retrofit – An investment made in an existing building or facility. May be equipment replacements, equipment add-ons, or shell and equipment improvements.

Return on Investment (ROI) – A performance measure used to evaluate the efficiency of an investment or to compare the efficiency of a number of different investments. To calculate ROI, the benefit (return) of an investment is divided by the cost of the investment; the result is expressed as a percentage or a ratio.

Safety Engineering – The planning, development, improvement, coordination and evaluation of the safety component of integrated systems of people,materials, equipment and environments to achieve optimum safety effectiveness in terms of protection of people and property.

Safety Shutoff Device – A device that will shut off the gas supply to the controlled burner(s) in the event the source of ignition fails. This device may interrupt the flow of gas to the main burner(s) only or to the pilot(s) and main burner(s) under its supervision.

Saturated Air – Aircontaining all the water vapor it can hold at its temperature and pressure.

Schematic – Anoutline, systematic arrangement, diagram, scheme, or plan. An orderly combination of events, persons, or things according to a definite plan. A diagram showing the relative position and/or function of different components or elements of an object or system.

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Sealed Burners – Gas burners that are sealed to prevent spillovers from reaching the burner box.

SeasonalEnergy Efficiency Ratio (SEER) – The energy efficiency measurement for central air conditioners is measured in a unit called SEER – seasonal energy efficiency ratio. The SEER is the cooling output divided by the power consumption, with climate and other variables factored in. The higher the SEER, the better – a rating of 10 is considered the minimum for new systems. Older systems might have a SEER of 7 or 8 – or even less. The SEER will be listed prominently on the yellow-and-black EnergyGuide.

Seasonal Gas – Seasonal gas is gas sold during certain periods of the year. It may be sold either on a firm or on an interruptible basis.

Secondary Air – The air for combustion externally supplied to the flame at the point of combustion.

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Shift Converter – A reactor which catalytically converts carbon monoxide and water into hydrogenand carbon dioxide.

Simple Payback – Installed cost of equipment divided by the annual energy savings.

Site vs. Source Efficiency – The efficiency of transporting energy from the point of extraction to the end user.

Solar Cell – A solar cell, also called a photovoltaic cell, is used to convert solar energy into electrical energy. Solar cells are the basic elements of a solar module (also known as a solar panel). Silicon is by far the commonest of a variety of semiconductors from which solar cells are made. A typical modern solar cell is squared-shaped measuring 10 cm × 10 cm. It is covered by a clear anti-reflection coating (ARC) that reduces the amount of light lost to reflection at the cell surface.

Source Efficiency – see Site vs. Source

Specific Heat – The heat required to raise a unit mass of a substance through a degree of temperature difference. Also, the ratio of the thermal capacity of a substance to that of water. The specific heat of fluids varies with temperature and pressure.

Standby Loss, Water Heater – The percentage of total energy stored in water which is lost each hour from a storage-type water heater.

Static Pressure – The force exerted per unit area by a gas or liquid, measured at right angles to the direction of flow, or the pressure when no liquid is flowing.

Steam Trap – A device for allowing the passage of condensate or air and condensate and preventing the passage of steam.

Steam Turbine – A type of motive equipment powered by steam used to drive mechanical apparatus. It has a rotary motion in contrast to a reciprocating motion.

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Steam, Exhaust – Generally, water vapor which has had most of the usable energy removed.

Steam, Live – Water vapor which includes recoverable energy.

Steam, Saturated – Steam at a temperature and pressure such that any lowering of the temperature or increase in pressure will cause condensation.

Steam, Super-Heated – Water vapor heated beyond the point at which complete vaporization occurs (100% quality).

Strategic Load Growth – A targeted increase in end-use consumption during certain time periods or among certain customer types. The result is a general increase in energy sales beyond the valley filling strategy. Strategic load growth may involve increased market share of loads that are, or can be, served by competing fuels, as well as area development.

Submetering – The practice of remetering purchased energy beyond the customer’s utility meter,generally for distribution to building tenants through privately owned or rented meters.

Substitute Natural Gas (SNG) – A gas manufactured from carbonaceous material whose characteristics are substantially interchangeable with natural gas. The resultant gas is composed primarily of methane. At this writing, SNG feedstocks are the light hydrocarbons, propane, butane, and the naphthas. Development is underway of processes for production from heavier feedstocks, coal, peat, and solid wastes.

Supplemental Gas – Any SNG, propane-air mixtures, refinery gas, biomass gas, and air injected to reduce heat content, or manufactured gas that is mixed and distributed with natural gas.

Sustained Pressure Test – A constant internal pressure test for an extended period of time. One thousand hours is a commonly used period.

Synthetic Natural Gas – A descriptive term used interchangeably with SNG and Substitute Natural Gas. It is a gas manufactured from naphtha, coal, etc., and is substituted for, or mixed with, natural gas by a pipeline or gasdistribution utility.

Telemetering – Useof an electrical apparatus transmitting data to a distant point for indicating, recording, or integrating the values of a variable quantity.

Temperature Limiting Device – A device which automatically interrupts the gas flow to the burner when the temperature exceeds the limitset.

Temperature, Ambient – Thetemperature of the air, atmosphere or other fluid that completely surrounds the apparatus, equipment or the work piece under consideration. For devices which do not generate heat, this temperature is the same as the temperature of themedium at the point of device location when the device is not present. For devices which do generate heat, this temperature is the temperature of themedium surrounding the device when the device is present and generating heat.Allowable ambient-temperature limits are based on the assumption that the device in question is not exposed to significant radiant-energy sources such as sunlight or heated surfaces.

Temperature, Critical – The temperature above which a fluid cannot exist as a liquid and hence cannot be liquefied by pressure alone.

Temperature, Dew-Point – The temperature at which a vapor begins to condense and deposit as a liquid.

Temperature, Dry Bulb – Technically, the temperature registered by the dry bulb thermometer of a psychrometer. It is identical with the temperature of the air.

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Temperature, Effective – An arbitrary index which combines into a single value the effect of temperature, humidity, and air movement on the sensation ofwarmth 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.

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Temperature, Ground – In the gas industry, the temperatureof the earth at pipe depth.

Temperature, Wet Bulb – The temperature an air parcel would have if cooled adiabatically to saturation at constant pressure by evaporation of water from it, all latent heat being supplied by the parcel.

Temperature-Compensated Meters – These meters measure volume temperature to volume at base temperature. These temperature compensators use a temperature-sensitive device to continuously vary the diaphragm-stroke to provide a temperature-compensated volume output. Meters equipped with temperature-compensators are often identified by red badges on the index face.

Therm – A unit of heating value equivalent to 100,000 British thermal units (Btu).

Thermostat – An automatic device actuated by temperature changes designed to control the gas supply to the burner(s) in order to maintain temperature between predetermined limits, and in which thethermal actuating element is an integral part of the device: 1. Electric Switch Type: A device which senses changes in temperature and control electrically, by means of separate components, the flow of gas to the burner(s) to maintain selected temperature. 2. Graduating Thermostat: A thermostat in which the motion of the thermostat valve is in direct proportion to the effective motion of the thermal element induced by temperature change. 3. Quick-Acting Graduating Thermostat: A thermostat which changes from the completely closed position, or vice versa, but not with a snap. 4. Snap-Acting Thermostat: A thermostat in which the thermostatic valve travels instantly from the closed to the open position, or vice versa.

Throughput – Total of transportation volumes and tariff sales; all gas volumes delivered.

Total Energy – A concept under which the electricity required by a given facility is producedon-site by natural gas and possible alternate standby fueled engines or turbines with the recovery of the equipment’s heat of rejection for space conditioning and/or process uses.

Trade Ally – In DSM (demand side management), an organization (architect, building contractor, etc.) that influences energy decisions of customers who are potential DSM (demandside management) program participants.

Transmission Company, Gas – A company which obtains at least 90% of its gas operating revenues from sales for resale and/or transportation of gas for others and/or main line sales to industrial customers and classifies at least 90% of its mains (other than service pipe) as field and gathering, storage, and/or transmission.

Trap – A device designed for removing liquids or solids from a gaseous stream; a low spot in a pipeline or main.

Tube, Finned – Heat transfer tube or pipe with extended surface in the form of fins, discs, or ribs.

Tube, Injection – A tube with a venturi throat which leads from the primary air port and gas orifice or a gas burner to mixing chamber and burner ports. As the gas passes from the gas orifice through the tube, it draws air through the primary airport into the mixing chamber, after which the mixture is burned at the burner ports.

Turbine, Steam or Gas – An enclosed rotary type of prime mover in which heat energy in steam or gas is converted into mechanical
energy by the force of a high velocity flow of steam or gas directed againstsuccessive rows of radial blades fastened to a central shaft. Compare ENGINE, RECIPROCATING.

Turbine Inlet Cooling (TIC) – TIC is cooling of the ambient air before it enters the compressor that supplies high-pressure air to the combustion chamber from which hot air at high pressure enters thecombustion turbine. TIC is also called by many other names, including combustion turbine inlet air cooling (CTIAC), turbine inlet air cooling (TIAC), combustion turbine air cooling (CTAC), and gas turbine inlet air cooling (GTIAC).

U-Factor – The quantity of heat transmitted per hour through one square foot of a building section (wall, roof, window, etc.) for each degree Fahrenheit of temperaturedifference between the air on the warm side and the air on the cold side of the
building section.

U.S. Green Building Council (USGBC) – A non-profit organization committed to expanding sustainable building practices. USGBC is composed of more than 15,000 organizations from across the buildingindustry that are working to advance structures that are environmentally responsible, profitable, and healthy places to live and work. Members includes building owners and end-users, real estate developers, facility managers, architects, designers, engineers, general contractors, subcontractors, product and building system manufacturers, government agencies, and nonprofits.

Ultimate CO2 – The maximum theoretical percentage of flue gas CO2 that is possible to produce from the complete combustion of a fuel with the chemically-correct fuel-air ratio.

Ultimate Reservoir Capacity – Total volume of gas within a reservoir which exerts a pressure from 0 pounds per square inch gauge pressure to the maximum or ultimate reservoir gauge pressure.

Ultimate Reservoir Pressure – The maximum reservoir pressure permitted by the geological configuration of the reservoir.

Vacuum – A pressure less than atmospheric pressure, measured either from the base of zero pressure or from the base of atmospheric pressure.

Vacuum-Relieving Device – A device to automatically admit air or gas into space at a pressure below atmospheric.

Valve – A mechanical device for controlling the flow of fluids and gases; types such as gate, ball, globe, needle, and plug valves are used.

Valve Box – A housing around an underground valve to allow access to the valve and to protect the valve from mechanical damage or the effects of weather.

Valve Chamber – The space in a dry gas meter containing the slide valves and mechanism for their operation.

Valve Control – A fuel-air control system that operates by means of mechanical linkage of related valves, common in industrial combustion systems.

Valve Seat – The stationary portion of the valve which, when in contact with the movable portion, stops flow completely.

Valve, Automatic Input Flow Control – A device for controlling the gas supply to the main burner without manual attention.

Valve, Automatic Shut-Off – A device designed to shut off gas flow upon flame failure, pilot outage, control impulse, overpressure, or under pressure without manual attention.

Valve, Back Pressure – A valve built to maintain agiven pressure in a piping system by remaining in a closed position until the given pressure is reached, at which time it opens to permit flow until the pressure falls below the specified pressure.

Valve, Check – Avalve built to pass a fluid in one direction but to close automatically when the fluid tries to flow in the opposite direction.

Valve, Expansion – A valve for controlling the flow of refrigerant to the cooling element.

Valve, Firing – A lubricated plug-type variable position valve which is usually operated with anattached handle or, in the large sizes, by a loose fitting key or extended handle wrench..

Valve, Main Burner Control – A valve which controls the gas supply to the main burner manifold.

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Valve, Manual Input Flow Control – A manual valve, usually withstops, which can be set to limit the gas flow to the maximum required input to the burner or burners.

Valve, Manual Main Shut-Off – A manually operated valve or stop in the gas line for the purpose of completely turning on or shutting off the gas supply to the appliance except to pilot or pilots which are provided with independent shut-off valves.

Valve, Manual Rest – An automatic shut-off valve installed in the gas supply piping and set to shut offwhen unsafe conditions occur. The device remains closed until manually reopened.

Valve, Relief – An automatic valve designed to discharge when a preset pressure and/or temperaturecondition is reached. 1. Pressure Relief Valve. An automatic valve which opens and closes a relief vent, depending on whether the pressure is above or below a predetermined value. 2. Temperature ReliefValve. A. Fusible Type. A valve which opens and keeps open a relief vent by the melting or softening of a fusible element at a predetermined temperature. B.Manual Reset Type. A valve which automatically opens a relief vent at a predetermined temperature and which must be manually returned to the closed position. C. Reseating or Self-Closing Type. An automatic valve which opens and closes a relief vent when the temperature reaches a predetermined value. D. Vacuum Relief Valve. An automatic valve which opens or closes a vent for relieving a vacuum, depending on whether the vacuum is above or below a predetermined value. Frequently used in a hot water supply system.

Valve, Safety Shut-Off (Cut-Off) – A valve which automatically shuts off the supply of fuel through the functioning of a flame safeguard control or limiting device. This device may interrupt the flow of fuel to the main burner(s) only or to the pilot(s) and main burner(s).

Valve, Shut-Off – Stops or valves readily accessible and operable by the consumer, located in the piping system (to shut off individual equipment) or between the meter and gas main to shut off the entire piping system.

Vapor – The gaseous state of a substance as distinguished from permanent gases. A gaseous fluid may be classified as either a vapor or a gas. If it is near the region of condensation, it is called a vapor. If it is well above the region of condensation, it is called a gas. Vapors in general do not follow the ideal gas law, and engineers prefer to use tables and charts based on experimental data when working with vapors. Gases, however, may obey the ideal gas laws over a wide range of temperature and pressure.

Vapor Barrier – A moisture-impervious layer applied to the warm side for the purpose of preventing moisture travel.

Vaporizer – A heat exchange used to return liquid natural gas to a gaseous form and then continue to heat the gas to a temperature at which it can be sent into the distribution system.

Variable Cost – Operating costs which, in the aggregate, vary either directly or indirectly in relation to any change in the volume of gas sold and/or transported; i.e., compressorstation fuel and expenses.

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Vent – An opening in a tank or other piece of equipment, sealed to prevent escape of material within the equipment at normal pressures but so arranged that it automatically opens to relieve excessive pressure in the equipment. Can be arranged for manual opening to depressure equipment as desired. Also, the relief opening in a pressure regulator, normally open to the atmosphere.

Vent Connector – That portion of the venting system which connects the gas appliance to the gas vent or chimney.

Vent Damper – A device installed in the vent pipe that connects the furnace to the chimney.When the burner goes off, the damper closes automatically, restricting the amount of heated air that can be lost through the chimney.

Vent, Flue Gas – A conduit or passageway for conveying flue gases to the outer air.

Ventilation – The process of supplying or removing air by natural or mechanical means to or from any space. Such air may or may not have been conditioned.

Ventilation Air – That portion of supply air which comes from outside, plus any recirculated air that has been treated to maintain the desired quality of air within a designated place.

Viscosity – In general, resistance to flow; that property of semi-fluids and gases by virtue of which they resist an instantaneous change of shape or arrangement of molecules.

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Water Heater Blanket – Insulated wrap attached to a water heater which supplements the insulation contained in the water heater.

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Water Heater Efficiency Measures – Energy Factor (EF) – A measure of the overall efficiency of a water heater based on its recovery efficiency, standby loss and energy input as set out in the standardized Department of Energy test procedures.

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Water Heater, Direct, Fired-An appliance for producing hot water for domestic or commercial purposes otherthan for space heating.

Water Heater , Tankless – Provide hot water only as it is needed. A tankless water heater is used only when there is a demand for hot water. They heat water directly without the use of a storage tank. Therefore, they avoid the standby heat losses associated with storage water heaters. In an electric Tankless Water Heater an electric element heats the water. In a gas-fired Tankless Water Heater a gas burner heats the water. As a result, Tankless Water Heaters deliver a constant supply of hot water.

Water Piping System, Closed – A heating system utilizing anair tank which provides a means of pressurizing the system for operation over a wide range of conditions and of circulating water which is used as a heat medium.

Water Source Heat Pump (geothermal heat pump) – Water source heat pumps, also known as geothermal heat pumps, use the constant temperature of the earth as the exchange medium instead of the outside air temperature. This allows the system to reach fairly high efficiencies (300%-600%) on the coldest of winter nights, compared to 175%-250% for air-source heat pumps on cool days.

Water to Carbon Ratio – The ratio by weight of the amount of water to carbon compounds in a gas (vapor) stream.

Water-Cooling Tower – A device for evaporative cooling of water by contact with air.

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Weatherization – The reduction of air infiltration by methods such as caulking and weather-stripping.

Yield Point – The stress at which a material exceeds its elastic limit. Below this stress, the material will recover its original size on removal of the stress. Above thisstress, it will not.

Zero Gas – Gas at atmospheric pressure.

Zone Heat – A central heating and/or cooling system which is arranged so that different temperatures can be maintained in two or more areas of the building being heated or cooled or simultaneously heated or cooled.