13 SEER - This is the new minimum efficiency standard (effective January 2006) for an air conditioner or heat pump. All new units must now meet this standard. Previously manufactured equipment (10, 11 and 12 SEER) may be used, sold, and installed. SEER is defined later.

80% A.F.U.E. - 80% of the fuel burned is turned into heat delivered at the register. The U.S. government's established minimum AFUE rating for a furnace is 78 percent.

AC Alternating Current - A type of current where the polarity is perpetually reversing, causing the directional flow in a circuit to reverse at regular intervals.

ACCA - The Air Conditioning Contractors of America, a national trade association that represents heating, ventilation, air conditioning, and refrigeration contractors.

A-Coil - A heat exchanger consisting of two diagonal coils that are joined together in the shape of the letter A.

Accumulator - A storage tank located in the suction line of a compressor.

ACH - Stands for Air Changes per Hour. It is the number of times in one hour that the air in your house is completely replaced with outside air.

Acid Condition - The presence of corrosive substances in a sealed refrigeration system.

Add On Heat Pump - Installing a heat pump in conjunction with an existing fossil fuel furnace. The result is a dual fuel system.

A.F.U.E (Annual Fuel Utilization Efficiency) - A rating that reflects the efficiency of a gas furnace in converting fuel to energy. A rating of 90 means that approximately 90% of the fuel is utilized to provide warmth to your home, while the remaining 10% escapes as exhaust.

AHU (Air Handler Unit) - The inside part of the A/C system that contains the blower, cooling (evaporator) coil, and heater. The part of an HVAC system responsible for moving air, which may also clean, heat, or cool the air. This refers to equipment used to provide conditioned air to a space. The air handler unit generally includes a blower or fan, heating and/or cooling coils, and related equipment such as controls, condensate drain pans, and air filters. Does not include ductwork, registers or grilles, or boilers and chillers.

Air Cooled System - A type of air conditioning system that uses freon as a refrigerant and air as a condensing medium. Typically, the air-cooled condenser is located outside and refrigerant lines are piped to it from the indoor unit.

Air Diffuser - Air distribution outlet or grille designed to direct airflow into desired patterns.

Air Flow - The distribution or movement of air.

Air Handler - The portion of the central air conditioning or heat pump system that moves heated or cooled air throughout a home's ductwork. This unit is usually located in the attic, utility room or closet or in a crawlspace. In some systems a furnace handles this function.

Allergen - A substance capable of causing an allergic reaction because of an individual's sensitivity to that substance

Allergic Rhinitis - Inflammation of the mucous membranes in the nose that is caused by an allergic reaction.

Aluminum Fin - Attached to a sleeve around the coil and used to dissipate heat away from the coil.

Air Change - The amount of air required to completely replace the air in a room or building; not to be confused with recirculated air.

Air Conditioner - A device that modifies the temperature, humidity, cleanliness, or general quality of air.

Air Conditioning - The science of controlling the temperature, humidity, cleanliness or general quality of air. Abbreviated: AC.

Air Cooled - Uses a fan to discharge heat from the condenser coil to the outdoors.

Air Diffuser - Air distribution outlet or grille designed to direct airflow into desired patterns.

Air Duct - Pipes that carry warm air and cold air to rooms and back to furnace or air conditioning system.

Air Exchange Rate - The rate at which outside air replaces indoor air in a space. Expressed in one of two ways: the number of changes of outside air per unit of time air changes per hour (ACH); or the rate at which a volume of outside air enters per unit of time - cubic feet per minute (cfm).

Airflow - The distribution or movement of air.

Air Handler - The portion of a central air conditioning or heat pump system that moves heated or cooled air throughout a home's ductwork. In some systems, a furnace handles this function.

Air Pressure Control (Switch) – Used to detect air pressure drop across the coil in a heat pump outdoor unit due to ice buildup.

Air-Source - Air is being used as the heat source or heat sink for a heat pump.

Ambient Temperature - The temperature of the immediately surrounding air or area.

Amperage - The rate of electrical current flow in a circuit.

ARI - Air-Conditioning and Refrigeration Institute is a non-profit, voluntary organization comprised of heating, air conditioning and refrigeration manufacturers. ARI publishes standards for testing and rating heat pumps and air conditioners to provide you with a standardized measure of comparison. So, ARI ensures a level of quality within the industry.

ASHRAE - American Society of Heating Refrigeration and Air Conditioning Engineers

Auto-Ignition - A feature of newer gas furnaces that eliminates the need for a standing pilot light. The system shuts off completely when not in use.

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B

Balance Point - An outdoor temperature -- usually between 30°F to 45°F -- at which a heat pump's output exactly equals the heating needs of the house. Below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort.

Balancing or Air Balancing - Adjusting an air conditioning system so that the right amount of air is delivered to the right places in your home in order to achieve the right heating or cooling effect.

Boiler - A sealed chamber in which water is converted to steam or is heated for circulation in a hydronic heating system.

Boiling Point - The temperature at which the addition of any heat will begin a change of state from a liquid to a vapor.

Blower - An air-moving device; a fan. An air handling device for moving air in a distribution system.

Boot - A fitting that connects round to rectangular sheet metal or fabricated duct systems.

Breaker - A heat-activated electrical device used to open an electrical circuit to protect it from excessive current flow.

BTU ( British Thermal Unit) - In scientific terms, it represents the amount of energy required to raise one pound of water one degree Fahrenheit. One BTU is the equivalent of the heat given off by a single wooden kitchen match. For your home, it represents the measure of heat given off when fuel is burned for heating or the measure of heat extracted from your home for cooling.

BTU/H or BTU/HR- The number of BTUs in an hour.

Burner - The device that facilitates the combustion of air and gas.

Burner Orifice - The opening in the burner through which the gas or fuel passes prior to combustion.

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C

Capacity - The output or producing ability of a piece of cooling or heating equipment. Cooling and heating capacity are normally referred to in BTUs. The ability of a heating or cooling system to heat or cool a given amount of space. For heating, this is usually expressed in BTUs. For cooling, it is usually given in tons.

Carbon Monoxide - Carbon Monoxide (CO) is a colorless, odorless gas produced by burning any fuel. CO is poisonous and symptoms of CO poisoning are similar to those of the flu: headaches, fatigue, shortness of breath, nausea and dizziness. The Consumer Product Safety Commission (CPSC) recommends a yearly, professional inspection.

Celsius - A temperature scale that registers the freezing point of water as 0° and the boiling point as 100° under normal atmospheric pressure.

Central Air Conditioner System - System in which air is treated at a central location and carried to and from the rooms by one or more fans and a system of ducts.

Central Forced-Air Heating System - A piece of equipment that produces heat in a centralized area, then distributes it throughout the home through a duct system.

CFC - Chlorofluorocarbons, used as a refrigerant in air conditioners and heat pumps, linked to the depletion of the ozone layer.

CFM - A standard of airflow measurement. Cubic feet per minute. A typical system produces 400 CFM per ton of air conditioning. The abbreviation for cubic feet per minute, commonly used to measure the rate of air flow in an air conditioning system.

Charge - Amount of refrigerant in a system.

Charging a System - Adding coolant, or refrigerant, to an HVAC system.

Chase - A groove in a masonry wall or through a floor to accommodate pipes or ducts.

Chimney or flue - A vent for the products of combustion.

Coefficient of Performance (COP) - A ratio calculated by dividing the total heating capacity provided by the heat pump, including circulating fan heat but excluding supplementary resistance heat (Btu's per hour), by the total electrical input (watts) x 3.412. (See Heating Seasonal Performance Factor, below.) Coefficient of Performance, COP, is the ratio of energy input to heating capacity. This is the instantaneous measurement of the heating performance of your heat pump. It is comparable to knowing how many miles per gallon of gasoline your car gets when it is going full speed. You can find the COP on the nameplate of your heat pump.

Comfort Zone - The range of temperatures, humidity and air velocities at which the greatest percentage of people feel comfortable.

Commissioning - The final step in installing a heating or air conditioning system. Every component is checked and tested for compliance with codes, ACCA manuals, manufacturer requirements, and occupant needs. After commissioning, the technician will: provide documentation of testing, provide all equipment manuals, and show the homeowner how to operate the system.

Compressor - The heart of an air conditioning or heat pump system. It is part of the outdoor unit that pumps refrigerant. The compressor maintains adequate pressure to cause refrigerant to flow in sufficient quantities to meet the cooling requirements of the system. Part of a split-system heat pump or air conditioner’s outdoor unit that controls the pressure applied to the refrigerant, necessary for taking in heat to warm your home or getting rid of heat to keep your home cool.

Compression - The reduction of volume of a vapor or gas by mechanical means.

Compression Ratio - The ratio determined by dividing the discharge pressure, in PSI, by the suction pressure in PSI.

Condensate/Condensation - Water vapor that liquefies due to the lowering of its temperature to the saturation point. The process by which a gas is changed into a liquid at constant temperature by heat removal.

Condensation Point - The temperature at which the removal of any heat will begin a change of state from a vapor to a liquid.

Condensate Drain - An outlet for the moisture collected on an evaporator coil.

Condensate Pump - A water pump that disposes of or recirculates collected condensate.

Condenser - A device that transfers unwanted heat out of a refrigeration system to a medium (either air, water, or a combination of air and water) that absorbs the heat and transfers it to a disposal point. There are three types of condensers: air-cooled condensers, water-cooled condensers, and evaporative condensers. The evaporative condenser uses a combination of air and water as its condensing medium. Most residential systems have an air-cooled condenser.

Condensing Unit - Part of a refrigerating mechanism which pumps vaporized refrigerant from the evaporator, compresses it, liquefies it in the condenser and returns it to the refrigerant control. The outdoor portion of a split system air conditioner contains the compressor and outdoor coil ignoring the reverse cycle operation, also the outdoor in a heat pump system.

Condenser Coil or Outdoor Coil - Located in the outdoor unit, the coil dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid. Part of the outdoor portion of a split-system air conditioner or heat pump. By converting refrigerant that is in a gas form back to a liquid, the coil sends heat carried by the refrigerant to the outside.

Condenser Fan - The fan that circulates air over an air cooled condenser. (usually located outside)

Condensing Furnace - A high-efficiency, gas forced-air furnace that uses a second condensing heat exchanger to extract the latent heat in the flue gas.

Condensing Unit - A complete unit that includes the compressor and the condensing coil.

Conditioned Air - Air that has been heated, cooled, humidified, or dehumidified to maintain an interior space within the "comfort zone".

Configuration - This describes the direction in which a furnace outputs heat. A furnace may have an upflow, down flow or cross flow (horizontal) configuration.

Contactor - A switch that can repeatedly cycle, making and breaking an electrical circuit. When sufficient current flows through a coil built into the contactor, the resulting magnetic field causes the contacts to be pulled in.

Convertible Air Handler - An air handler that can be installed in either an upflow or a horizontal left configuration.

Cooling Capacity - A measure of the ability of a unit to remove heat from an enclosed space.

Cooling Load - Heat which flows into a space from outdoors and/or indoors.

Copper Coil - Coils move refrigerant under high pressure and copper is known for its durability and efficient heat transfer.

CSA - Canadian Standards Association.

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D

DC - Direct Current. A type of electrical current that only flows in one direction.

Data Plate - An equipment identification label; usually lists model and serial numbers and various unit ratings.

Damper - Found in duct work, this movable plate opens and closes to control airflow. Dampers are used effectively in zoning to regulate airflow to certain rooms. A type of "valve" used in duct work that opens or closes to control airflow. Used in zoning to control the amount of warm or cool air entering certain areas of your home.

Decibel (db) - A decibel describes the relative loudness of a sound. Some common sounds are fairly close to a typical air conditioner or heat pump's sound level: human voice, 7.0 decibels; blender, 8.8 decibels.

Defrost Cycle - The process of removing ice or frost buildup from the outdoor coil during the heating season.

Defrost Mode - During the heating cycle of a heat pump, frost may build up on the outdoor coil. To remove the frost and maintain efficiency, the system will automatically defrost itself. This usually only takes a few minutes, then the system automatically switches back to heating. It is normal to see steam rising from the outdoor unit when this happens.

Degree Day - The difference between indoor design temperature and each day's average outdoor temperature. Abbreviated: DD.

Dehumidification - The reduction of water vapor in air by cooling the air below the dew point; removal of water vapor from air by chemical means, refrigeration, etc.

Dehumidify - To remove moisture from air.

Direct Expansion Systems - One of two types of basic cooling media (the other is chilled water). Direct expansion systems utilize freon for cooling and dehumidification. The three most common methods of heat rejection are air cooled, water cooled and glycol cooled.

Direct Vent - Pulls outside air for combustion and vents combustion gases directly outside.

Disconnect - A switch box that cuts off electrical power to a machine being serviced.

DOE - The Department of Energy - A federal agency that sets industry efficiency standards and monitors the use of various energy sources.

Downflow Furnace - A furnace that pulls in return air from the top and expels warm air at the bottom. A type of furnace that takes cool air from the top and blows warm air to the bottom—common where your furnace must be located in a second-floor closet or utility area.

Duct - A pipe or closed conduit made of sheet metal, fiberglass board, or other suitable material used for conducting air to and from an air handling unit. Conduits used to carry air. They can be round or rectangular, sheet metal or fiberglass or vinyl tubes. In air conditioning systems they carry air from the home to the air conditioning system or furnace and back to the home.

Duct Heater - An electric-resistance or hot water heater mounted inside an air-delivery duct to provide supplementary heat to the delivered air.

Ductless Mini-Split System - A system where there is no ductwork involved, simply a single indoor unit (usually wall mounted) or two or more indoor units and a single outdoor unit (condensing unit/heat pump) Used to heat and cool areas where traditional ductwork is not feasible such as additions, workshops, warehouse offices, enclosed porches, etc.

Ductwork - Pipes or channels that carry air throughout your home.

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E

Energy Efficiency Ratio (EER) - A ratio calculated by dividing the cooling capacity in Btu's per hour (Btuh) by the power input in watts at a given set of rating conditions, expressed in Btuh per watt (Btuh/watt). (See Seasonal Energy Efficiency Ratio,below.)

Efficiency - The amount of usable energy produced by a machine, divided by the amount of energy supplied to it. A rating on comfort equipment is similar to the miles per gallon rating on your car. The higher the rating number, the more efficient the system and the lower your fuel consumption will be.

Elbow - Any fitting that produces a bend in the duct or piping run it connects.

Electric Heat - A heating system in which the energy source is electricity and the heat is produced by resistance elements.

Electronic Air Cleaner (EAC) - A filter that uses electricity to create a slight magnetic charge to help collect smaller particles. The EAC then draws tiny particles that are magnetized, such as viruses and bacteria, to a collector plate to remove them from the indoor air in your home. An electronic device that filters out large particles and contaminants in indoor air. It then electronically pulls out tiny particles that have been magnetized, such as viruses and bacteria, drawing them to a collector plate.

Electronic Leak Detector - A test instrument that detects the presence of refrigerants in small air samples.

Electrostatic filter or Precipitator - An air cleaning device that electrically charges foreign particles in the air and then collects them on positively charges plates.

Emergency Heat (Supplementary Electric Heat) - The back up electric heat built into a heat pump system. The same as an auxiliary heater, except it is used exclusively as the heat source when the heat pump needs repair.

Energy Star® - EPA rating given to products that exceed a standard efficiency level of operating costs of H.V.A.C. equipment. When properly installed, Energy Star-labeled products can save consumers 10-40% on heating and cooling bills each year. A government supported branding used to identify energy efficient products. The branding was developed by the US Department of Energy and the US Environmental Protection Agency.

Enthalpy - Heat content or total heat, including both sensible and latent heat. The amount of heat contained in a refrigerant at any given temperature with reference to -40°F.

E.P.A. - Environmental Protection Agency

ERV - Energy Recovery Ventilator, a machine that draws fresh air into the home and exhausts stale air from the home. It uses a process to preheat or pre-cool (depending on the season) to reduce energy costs associated with conditioning the air.

Evacuate - To remove, through the use of a vacuum pump, all moisture and noncondensables from a system.

Evaporator Coil - The coil that is inside your house in a split system. In the evaporator, refrigerant evaporates and absorbs heat from air passed over the coil. Part of a split-system air conditioner or heat pump located indoors. The evaporator coil cools and dehumidifies the air by converting liquid refrigerant into a gas, which absorbs the heat from the air. The warmed refrigerant is then carried through copper tubes to the outdoor unit (condenser coil).

Expansion Valve - A valve that meters the levels of refrigerant through a temperature or pressure control.

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F

Fahrenheit - The temperature scale on which water freezes at 32 deg. And boils at 212 deg.

Fan Coil - Another term for air handler. Which is generally the indoor section of a heat pump system which is made up of a blower and refrigerant coil. An indoor component of a heat pump system, used in place of a furnace, to provide additional heating on cold days when the heat pump does not provide adequate heating.

Fill-Type Insulation - Loose insulating material which is applied by hand or blown into wall spaces mechanically.

Filter - A device used to remove dust and other particles from air for the purposes of reducing the load on the respiratory system and to protect the HVAC equipment. Filters vary greatly in particle arrestance; the higher the MERV rating, the better the filter.

FLA (Full Load Amperage) - The current draw of a motor under full load, the current flow in a circuit when the load is at its rated peak.

Flexible Duct - A duct that can be gradually bent to go around obstacles.

Flue - A vent that carries the products of combustion from a boiler or furnace.

Forced Air - This describes a type of heating system that uses a blower motor to move air through the furnace and into the ductwork.

Free Delivery - There are no ducts and the unit may be installed in the field without ducts if needed. Ground-Source - The ground or soil below the frost line is being used as the heat source or heat sink for a heat pump.

Freon - A general term used to identify, any of a group of partially or completely halogenated simple hydrocarbons containing fluorine, chlorine or bromine, which are used as refrigerants.

Fungi - Any of a group of parasitic lower plants that lack chlorophyll, including molds and mildews.

Furnace - That part of an environmental system which converts gas, oil, electricity or other fuel into heat for distribution within a structure.

Fuse - A metal strip in an electrical circuit that melts and breaks the circuit when excessive current flows through it.

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G

GAMA - Gas Appliance Manufacturing Association is a national trade association serving the interests of manufacturers of gas, oil, and electric appliances and equipment, components and related products used in residential, commercial, and industrial applications.

Gas Furnace Heat Exchanger - Located in the furnace, the heat exchanger transfers heat to the surrounding air, which is then pumped throughout your home.

Gas Valve - A valve that controls fuel flow to the burner in a gas-fired furnace or heater.

Glycol-Cooled System - A type of air conditioning system that uses freon as a refrigerant and a water/glycol solution as a condensing medium. Typically, the glycol-cooled condenser is located inside the air conditioner with the rest of the refrigeration components. Water/glycol is piped to the unit from a drycooler or other suitable source. The glycol keeps the solution from freezing during winter operation.

Grille - A cage-like panel that covers the end of a duct, permitting the passage of air but not foreign objects.

Ground Water-Source - Water from an underground well is being used as the heat source or heat sink for a heat pump.

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H

HCFC - Hydrochlorofluorocarbons, used as a refrigerant in air conditioners and heat pumps. HCFCs were thought to contribute to the depletion of the earth’s ozone layer.

Head Pressure - High-side pressure in a refrigeration system; pressure from the compressor discharge to the metering device.

Head Exchanger - A device for the transfer of heat energy from the source to the conveying medium.

Heat Gain - The amount of heat gained, measured in BTU's, from a space to be conditioned, at the local summer outdoor design temperature and a specified indoor design condition.

Heat Loss - The amount of heat lost, measured in BTU's from a space to be conditioned, at the local winter outdoor design temperature and a specified indoor design condition.

Heat Pump - An electric air conditioning and heating system that captures existing outdoor heat and transfers or "pumps" this heat into your home. The most common type is an "air to air" meaning heat is captured from the outside air and transferred to the air inside your home. A heat pump is basically an air conditioner with a reversible valve that allows it to operate in reverse, removing heat from your house and shunting it outdoors in the summer, and removing heat from outdoor air and shunting it into your house in the winter. Because heat pumps do not actually create heat - they just move it from one place to another - heat pumps are more efficient than other forms of heating.

Heat Source - A body of air or liquid from which heat is collected. In an air source heat pump, the air outside the house is used as the heat source during the heating cycle.

Heat Strip - The supplemental or primary heating "coil" that produces heat using electrical resistance.

Heat Transfer - The movement of heat from one place to another, between two substances, or within a substance.

Heating Capacity - A measure of the ability of a unit to add heat to an enclosed space. The rate at which a specific device can add substantial heat to a substance, expressed in BTUh (British Thermal Units per hour).

Heating Degree Days - The number of degrees per day that the daily average temperature (the mean of the maximum and minimum recorded temperatures) is below a base temperature, usually 65 degrees Fahrenheit, unless otherwise specified; used to determine indoor space heating requirements and heating system sizing. Total HDD is the cumulative total for the year/heating season. The higher the HDD for a location, the colder the daily average temperature(s).

HFC - Hydroflorocarbon, used as a refrigerant in air conditioners and heat pumps. It has little or no effect on the ozone layer.

High-Efficiency Gas Furnace - A furnace that recycles combustion gases to obtain efficiencies of 85% to 95%.

High Side - A term used to indicate the high-pressure or condensing side of the refrigeration system.

Horizontal Flow - A type of furnace, installed on its "side," that draws in air from one side, heats it and sends the warm air out the other side. Most often used for installations in attics or crawl spaces.

Horizontal Furnace - A type of furnace most often installed in attics or crawl spaces. The furnace is installed on its side and draws air in from one side, heats it and emits warm air out the opposite side.

HRV - Heat Recovery Ventilator, a machine that brings fresh air into a home through a process that preheats the air so it has less impact on your utility bill.

HSPF = Heat Pump Heating Efficiency - It stands for Heating Seasonal Performance Factor, or HSPF. The higher the HSPF rating, the more efficient a heat pump is at heating your home. The US government has established a minimum 6.8% HSPF.

Humidifier - A piece of equipment that adds water vapor to heated air as it moves out of the furnace. This adds necessary moisture to protect your furnishings and reduce static electricity.

Humidistat - A device designed to regulate humidity input by reacting to changes in the moisture content of the air.

Humidity - The amount of moisture in the air. Air conditioners remove moisture for added comfort.

HVAC - Industry acronym for the general category of Heating, Ventilation, and Air Conditioning

HVACR - Industry acronym for the general category of Heating, Ventilating, Air conditioning, and Refrigeration

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I

IAQ - Acronym for Indoor Air Quality

ICM - Integrally Controlled Motor. A specially engineered, variable-speed motor used in American Standard's top-of-the-line indoor units. ICM motors are more than 90% efficient versus 60% efficiency for conventional motors. Continuous comfort, whisper-quiet operation and ultimate system efficiency are the benefits of the indoor products graced with the ICM motor.

Ignition - Elevating the temperature of a substance to the point of causing a combustion reaction.

Indoor Air Quality - The purity of indoor air or a lack of polluting gases or particles given off by equipment and furnishings in a space that can affect human health.

Indoor Coil - The portion of a heat pump or central air conditioning system that is located in the house and functions as the heat transfer point for warming or cooling indoor air.

Indoor Unit - This is usually located inside the house and contains the indoor coil, fan, motor, and filtering device, sometimes called the air handler.

Induced-Draft Furnace - A furnace in which a motor-driven fan draws air from the surrounding area or from outdoors to support combustion.

Infiltration - Air flow into a space usually through walls and leaks around doors and windows. Air that enters your home through holes, gaps, and cracks, (e.g., plumbing or electrical holes, the heating and air conditioning system, doors, and windows).

Insulation - Any material that slows down the transfer of heat.

Integrally Controlled Motor (ICM) - A variable-speed motor that operates at low RPM when possible for efficiency and quiet operation. ICM motors are more than 90% efficient versus 60% efficiency for conventional motors.

ISO 9000 Standards - The International Organization of Standards (ISO) 9000 standards define a Quality System which ensures the quality of a product.

ISO 9001 - The model for Quality Assurance in Design, Development, Production, Installation and Servicing. ISO registration is just one of the building blocks for achieving world-class products.

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J

No entries at current time.

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K

(K) Factor - The insulating value of any material. Also known as conductivity.

Kilowatt (Kw) - Equal to 1,000 watts.

Kilowatt-hour (Kwh) - A common unit of electrical consumption measured by the total energy created by one kilowatt in one hour.

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L

Latent Cooling Capacity - An A/C system's capability to remove moisture from the air.

Latent Heat - The heat energy needed to change the state of a substance (i.e.: from a liquid to a gas) but not it's temperature.

Life Cycle Cost - The sum of all the costs both recurring and nonrecurring, related to a product, structure, system, or service during its life span or specified time period.

Lifetime Cost - The cost of something, including purchase, operation, maintenance, and disposal costs.

Limit Switch - A protective device used to open or close electrical circuits when temperature or pressure limits are reached.

Line Drier - An accessory that removes moisture from a refrigeration system.

Line Set - A term used for tubing sets furnished by the manufacturer for connecting parts of an air conditioning system.

Liquid Line - The refrigerant tubing extending from the condenser outlet to the metering device. Usually the small warm line.

Load Calculation - A mathematical design tool used to determine the heat gain and heat loss in a building so that properly sized air conditioning and heating equipment may be installed.

Load Estimate - Studies performed to calculate heating and cooling requirements for a specific house, using the size of your home, size of your windows and doors, quality of insulation, and local weather conditions.

Locked Rotor Amperage (LRA) - The current drawn by a motor at start-up, before the rotor starts turning.

Louver - An opening with horizontal slats to permit passage of air, but excluding rain, sunlight and view.

Low Side - a term used to refer to that part of the refrigeration system that operates at the lowest pressure, between the expansion device and the compressor.

LP Fuel (Liquefied Petroleum) - A substance used as a gas for fuel. It is transported and stored in the liquid state.

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M

Manual D® - An ACCA procedure covering the proper design, installation, maintenance, and repair of ductwork.

Manual J® - An ACCA procedure covering the method for calculating heating and cooling requirements (load calculation) for single-family detached homes and mobile homes.

Manual RS® - An ACCA publication covering the design, installation, and commissioning of a residential HVAC system.

Matched System - A heating and cooling system comprised of products that have been certified to perform at promised comfort and efficiency levels when used together, and used according to design and engineering specifications.

Media - The fine material of a filter that traps dirt, dust, mildew or bacteria.

Mold - A natural byproduct of the fungi family that thrives when organic substances and water combine under certain circumstances. Mold reproduces via spores that can remain dormant, yet viable, for years. Many molds are beneficial. For example, they are the “bleu” in bleu cheese, and we use them to make wine, penicillin, and antibiotics. However, some molds can cause health problems.

Multi-Position - An indoor air handler or furnace that can be installed as an upflow (ductwork overhead or in the attic), downflow (ductwork in a basement or crawl space), or horizontal (air handler or furnace in a basement or attic) application, depending on individual need.

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N

NATE - North American Technician Excellence, the nonprofit organization that tests and certifies HVACR technicians.

National Electrical Code (NEC) - Publication that sets the standards for all electrical installations, including motor overload protection.

Natural-Draft Furnace - A furnace in which the natural flow of air from around the furnace provides the air to support combustion. It also depends on the pressure created by the heat in the flue gases to force them out through the vent system.

Natural Gas - A fossil fuel formed over millions of years from dead vegetation and animals that were deposited or washed deep into the earth.

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O

OEM - Original equipment manufacturer.

Operating Cost - The cost of running your heating and air conditioning system, day-to-day, based on energy use.

Orifice - An opening or hole.

Overcharge - To fill a system with refrigerant beyond its design capacity.

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P

Package System - A piece of air conditioning and heating equipment where all components are located in one cabinet. Used occasionally in residential applications, the package unit is installed either beside or on top of the home.

Package Unit - Any system that is self-contained in an outdoor package - no indoor section is required. Typically used in rooftop or mobile home applications.

Payback - The amount of time required (usually in years) for positive cash flows to equal the total investment costs. This is often used to describe how long it will take for energy savings resulting from using more energy-efficient equipment to equal the premium paid to purchase the more energy-efficient equipment.

Payback Analysis - An overall measurement of the efficiency and value of your heating and air conditioning system. Payback analysis is used to measure the period of time required to add up the energy saving on higher efficient equipment against the purchase price of that equipment. Or to calculate the monthly energy savings against the monthly payments to purchase an upgrade.

Plenum - A chamber which can serve as a distribution area for heating or cooling systems, generally between a false ceiling and the actual ceiling. A sealed chamber at the inlet or outlet of an air handler. The duct attaches to the plenum.

PMA - Planned maintenance agreement, which provides regular maintenance of your HVACR system. Most ACCA member contractors offer PMAs, although they may use different names for them, such as Maintenance Inspection Agreement, Planned Service Agreement, Energy Service Plan, etc.

Preventative Maintenance - The scheduled inspection and replacement of short-lived components in order to avoid untimely and expensive emergency repairs.

Programmable Thermostat - A thermostat with the ability to record different temperature settings for different times for your heating and/or cooling equipment. Programmable thermostats can be electronic, or mechanical.

Propane - An LP gas used for heat.

PSI - Pounds per square inch.

PSIA - Pounds per square inch, absolute.

PSIG - Pounds per square inch gauge.

Pump Down - To use the compressor to pump all of the system's refrigerant into the receiver and/or condenser prior to opening the system for service. This is also used in commercial systems to prevent refrigerant migration in the off cycle.

PVC - Polyvinyl chloride; a type of plastic.

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Q

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R-22 - A refrigerant containing chlorine used in air conditioning systems. The EPA has mandated that R-22 cannot be manufactured after 2010 because it has been linked to the depletion of the ozone layer and global warming. Most commonly referred to by its trademarked name, Freon.

R-410A - The refrigerant that will replace R-22 in the HVAC equipment manufacturing process. It does not contain chlorine and is not hazardous to the environment.

R Value - Term used to measure the level of effect of insulating products that lower temperature transfer.

Radiant Heat - Coils of electricity, hot water or steam pipes embedded in floors, ceilings, or walls to heat rooms.

Reciprocating Compressor - A type of compressor used in air conditioners that compress refrigerant by using a type of "piston" action.

Recirculated Air - Indoor air that is taken in from the conditioned space and sent through the HVAC system. It must be mixed with sufficient outdoor air to prevent the build-up of contaminants.

Reclaiming - The practice of returning used refrigerant to the manufacturer for disposal or reuse.

Recycling - The practice of removing, cleaning and reusing refrigerant.

Refrigerant - A chemical that produces a refrigerating effect while expanding and vaporizing. Most residential air conditioning systems contain R-22 refrigerant. R-22 is regulated by international controls under the Montreal Protocol and in the United States by the Environmental Protection Agency. It is scheduled to be in production until the year 2020. It's used in approximately 95 percent of air conditioning equipment manufactured in the U.S. today.

Refrigerant Charge (or, “charging the refrigerant”) - The procedure an HVACR technician performs to ensure that the system has enough of the right kind refrigerant for proper and peak operating performance.

Refrigerant Lines - Two copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil.

Refrigerant Recovery - The process of removing refrigerant from a system and placing it in a container.

Register - Combination grille and damper assembly covering an air opening or end of an air duct.

Relative Humidity (RH) - The ratio of the amount of vapor contained in the air to the greatest amount the air could hold at that temperature. Normally expressed as a percentage. The percent of moisture actually in the air compared to the maximum amount of moisture the air can hold at that temperature.

Relay - An electrical switch controlled by the flow of current in a separate or parallel circuit.

Remote System - Often called a split system where the condenser is located away from the evaporator and/or other parts of the system. See Split System.

Return - The ductwork through which air is returned to the source for re-conditioning. The path the air takes to get to an air-handling unit or furnace so it can be cooled or heated. It is the “return” path. The return side should be “balanced” with the supply side to ensure proper air flow and comfort.

Return Air - Air drawn into a heating unit after having been circulated from the heater's output supply to a room.

Return Intake - An opening through which air is exhausted from a conditioned space.

Reversing Valve - An electrical, four-way valve in a heat pump that diverts refrigerant flow according to whether cooling or heating is needed; also called a four-way valve.

Roof Top Unit - A HVAC unit located on the roof.

Running Time - The time a unit operates. Also called the on time.

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