Industry Terminology

Advanced Reciprocating Compressor Type of compressor that uses a more efficient process for compressing refrigerant for better cooling efficiency.
Afue Annual Fuel Utilization Efficiency is indicated as a percentage. Your furnace's AFUE tells you how much energy is being converted to heat. For example, an AFUE of 90 means that 90% of the fuel is being used to warm your home, while the other 10% escapes as exhaust with the combustion gases.
Ahri The Air Conditioning, Heating, and Refrigeration Institute (AHRI) is a North American trade association that represents HVAC manufacturers, and tests equipment to ensure government standards are met.
Ahri Reference Number All HVAC equipment tested and certified by AHRI receives a unique reference number.
Air Cleaner An HVAC product designed to filter pollutants out of indoor air.
Air Handler The portion of your air conditioner or heating system that forces air through your home's ductwork.
Airflow The amount of air an HVAC system can move in cubic feet per minute.
Air-side Economizer A controlled means by which an HVAC system introduces fresh air into a space to alleviate the need for artificial cooling in mild/cold weather conditions.
Aoh Based on geographical factors and anticipated weather conditions, annual operating hours (AOH) estimate the number of hours an air conditioner, furnace, or other HVAC unit might typically operate in a year.
Ashrae ASHRAE is a global organization focused on sustainable, built environment technology. Formerly the American Society of Heating, Refrigeration, and Air Conditioning Engineers.
Blower In HVAC, the device in an air conditioner that distributes the filtered air from the return duct over the evaporator coil or heat exchanger. This circulated air is cooled or heated and then sent through the supply duct, past dampers and through supply diffusers to the living or working space.
Boiler A vessel or tank where heat produced from the combustion of fuels such as natural gas, fuel oil or coal is used to generate hot water or steam for applications ranging from building space heating to electric power production or industrial process heat.
Btu British Thermal Unit. Used for both heating and cooling, BTU is a measure of the heat given off when fuel is combusted. Or for cooling, it's a measure of heat extracted from your home.
Btu/h A British Thermal Unit (BTU) is the unit of heat required to raise 1 pound of water by 1 degree Fahrenheit. BTU/H is British Thermal Units per Hour.
Building Envelope Elements of the building, including all external building materials, windows and walls that enclose the internal space.
Capacity The ability of a heating or cooling system to heat or cool a given amount of space. For heating, this is usually expressed in BTU's. For cooling, it is usually given in Tons.
Carbon Monoxide A colorless, odorless, highly poisonous gas produced when carbon-based fuels, such as natural gas, burns without sufficient air nearby. Carbon monoxide is produced in the incomplete combustion of carbon and carbon compounds such as fossil fuels (i.e. coal, petroleum) and their products (e.g. liquefied petroleum gas, gasoline) and biomass.
Ceer CEER stands for Combined Energy Efficiency Ratio and is most typically associated with room air conditioner or window air conditioner HVAC units. CEER measures the combined efficiency of the unit when it is in standby and when it's actually cooling a space.
Ceiling Plenum Space below the flooring and above the suspended ceiling that accommodates thmechanical and electrical equipment and that is used as part of the air distribution system. The space is kept under negative pressure
Central Air Conditioning System System in which air is cooled at a central location and distributed to and from rooms by one or more fans and a series of ducts.
Central Air Handling Unit The same as an Air Handling Unit, but serves more than one area.
Certified Matched System A heating and cooling system comprised of equipment that has been certified to perform at certified efficiency levels when used together, and used according to design and engineering specifications.
Cfc Chlorofluorocarbon (CFC) refrigerants are ozone-depleting chemicals once used as air conditioner and heat pump refrigerants.
Cfm Stands for Cubic Feet per Minute. A measurement of airflow that indicates how many cubic feet of air pass by a stationary point in one minute. The higher the number, the more air is being forced through the system. 1 CFM equals approximately 2 liters per second (l/s).
Chiller Chiller systems remove heat from water in large-scale cooling applications.
Combustion Combustion takes place when gaseous, liquid or solid fuels react at an elevated temperature with oxygen by burning, thus releasing heat.
Compressor 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 with a heat pump or getting rid of heat to keep your home cool.
Condensate The liquid that separates from a gas due to a reduction in temperature or an increase in pressure.
Condenser The device in an air conditioner or heat pump in which the refrigerant condenses from a gas to a liquid when it is depressurized or cooled.
Condenser Coil 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. This will return the hot vapor that entered the coil into a hot liquid upon exiting the coil.
Condensing Furnace This is a furnace with an AFUE of 89% or higher. Efficiency is achieved by extracting heat from the exhaust gases to the point where water is condensed out of the gases.
Conditioned Air Air that has been heated, cooled, humidified, or dehumidified to maintain an interior space within the "comfort zone."
Cop Coefficient of Performance (COP) is a metric for measuring performance efficiency. Higher COP is better than lower COP.
Damper 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.
Db Decibels (dB) are a unit measuring the intensity of noise.
Defrost The defrost cycle on an HVAC system is used to melt accumulated ice.
Doe Abbreviation for the U.S. Department of Energy, the federal agency responsible for setting national appliance efficiency standards and monitoring the consumption of energy sources.
Downflow A type of furnace that takes cool air from the top and blows warm air to the bottom-commonly used where furnaces must be located in a second-floor closet or utility area.
Dry-charged Unit A dry-charged unit is any air conditioner or heat pump system shipped from the factory without refrigerant pre-charged in the coils.
Dual Fuel A heat pump and furnace combination system that uses both electricity and gas to heat.
Ductwork Hollow pipes used to transfer air from the Air Handler to the air vents throughout your home. Ductwork is one of the most important components of a home heating and cooling system.
Eer Energy Efficiency Ratings (EER) measure the efficiency with which a product uses energy to function. It is calcuated by dividing a product's BTU output by its wattage.
Electric Heat Strip An electric heat strip looks like a series of coils. It attaches to the air handler on an air conditioning system and then heats the air coming out of the blower using radiant heat (with the AC in “fan only” mode). Essentially, it converts the air handler into a small-scale electric furnace.
Electronic Air Cleaner An electronic device that filters out large particles and bio-aerosols in indoor air.
Electronic Air Cleaner (Eac) 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.
Energy Factor Energy Factor (EF) is the amount of energy delivered as heated water in a day divided by the total daily energy consumption of a residential water heater. The EF is used to compare the energy efficiency of water heater models. Water heaters with higher EFs will have lower annual operating costs than comparable models with lower EFs.
Energy Guide Label A bright yellow tag indicating how much energy an appliance uses, and the estimated annual operating cost.
Energy Input Rating The amount of input energy delivered at the burner of furnaces, water heaters and boilers, measured in British thermal units (BTUs) per hour.
Energy Saver Switch An energy-saver switch causes the air conditioner's fan and compressor to cycle on and off together, reducing energy use.
Energy Star Energy Star is a government-backed program helping businesses and individuals protect the environment through superior energy efficiency. Products with the Energy Star rating will be efficient and save cost on energy bills.
Epa An abbreviation for the U.S. Environmental Protection Agency, the federal agency that develops and enforces federal environmental regulations. The EPA oversees the nationwide ENERGY STAR® program.
Evaporator 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 (or vice-versa). A blower moter, typically in a furnace, then moves air over the coil to either heat or cool your home.
Fan Coil An indoor component of an air conditioner or heat pump system, used in place of a furnace and evaporator coil, to provide change the refrigerant from a gas to a liquid (or vice-versa) and blow air over the coil to cool or heat your home.
Fhr First Hour Rating (FHR) is a measure of the capacity of a water heater referring to the amount of hot water a tank water heater can supply in an hour starting with a full tank of hot water. The number is stated in gallons and is found on the top left corner of the Energy Guide label.
Flow Rate The amount of water in gallons flowing past a fixed point over a period of time, typically expressed in gallons per minute.
Flue The passageways in heating equipment and vents through which combustion products pass to the outside atmosphere.
Flue Collar The portion of a gas appliance designed for the attachment of a venting system.
Flue Damper When a combustion heating system comes on, the flue damper automatically opens access to the flue, so that potentially damaging byproducts can be expelled safely.
Furnace A combustion heating system that will keep your home warm in cold weather.
Fvir Technology Flammable vapor ignition-resistance technology prevents the ignition of flammable vapors around your water heater. All gas-fired residential tank water heaters manufactured since July 1, 2003, must have this technology.
Gama The GAMA Efficiency Rating Certified logo appears on space and water heating equipment that has been certified by the Air-Conditioning, Heating and Refrigeration Institute. It is your guarantee that the equipment’s energy-efficiency ratings have been independently verified by a third party. Space and water heating equipment displaying the GAMA emblem includes furnaces, water heaters, boilers and direct heating equipment.
Gas Furnace A combustion furnace fueled by natural gas.
Gas Pack An HVAC system that houses both cooling and gas heating components in the same cabinet.
Geothermal An energy efficient heat pump design that uses the Earth as its heat source and sink.
Heat Exchanger The part of a furnace that transfers heat to nearby air.
Heat Pump A product that works just like an air conditioner in cooling mode; however, in heating mode, the refrigerant flow is reversed and heat is extrated from the outside air too heat your home.
Hepa Filter A High Efficiency Particulate Absorption (HEPA) filter can remove pollen, dust, mold, and other particulate pollutants from indoor air.
Horizontal Flow A Horizontal Flow unit is a design that draws air into one side of a cabinet, then expels the air into ductwork or a conditioned space connected to the other side.
Hspf The Heating Seasonal Performance Factor is a measure of the heating efficiency of a heat pump. The higher the HSPF number, the more efficiently the heat pump heats your home.
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 The humidistat is an HVAC tool that can automatically monitor and manage the humidity level in your home.
Humidity In an HVAC context, humidity is a measure of the moisture level in your home air.
Hvac Term used for Heating, Ventilation, and Air Conditioning.
Hybrid Heat Hybrid Heat systems deliver exceptional performance by using a heating source that provides the most energy-efficient comfort during moderate heating conditions.
Iap Indoor air polution
Iaq Indoor air quality
Indoor Coil See Evaporator Coil
Infiltration Air leakage inward through cracks and interstices and through cielings, floors, and walls of a space or building.
Ion An electrically charged atom or group of atoms that has lost or gained electrons; a loss makes the resulting particle positively charged; a gain makes the particle negatively charged.
Kilowatt Kilowatt (kW) is a measure of electrical power equal to 1000 watts.
Leed Leadership in Energy and Environmental Design (LEED) is a program to certify buildings that are environmentally conscious in construction, design, and daily operation.
Lineset In a heating and air conditioning system, a lineset is the conduit for refrigerant to move between interior and exterior components.
Load Calculation A load calculation can be performed to determine a building's ideal HVAC system production capacity.
Load Estimate A series of studies performed to determine the heating or cooling requirements of your home. An energy load analysis uses information such as the square footage of your home, window or door areas, insulation quality and local climate to determine the heating and cooling capacity needed by your furnace, heat pump or air conditioner. When referring to heating, this is often known as a Heat Loss Analysis, since a home's heating requirements are determined by the amount of heat lost through the roof, entry ways and walls.
Louver A louver is a system of blades, sometimes adjustable, in a duct or frame to manipulate air movement.
Low Boy Low Boy is a type of furnace configuration in which the furnace is lower in height and occupies more floor space.
Manual J Calculation The Manual J Calculation is a load calculation specifically for residential HVAC systems. If you don't know what size air conditioner you need for your home, a Manual J Calculation will tell you.
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 Filter A media filter is the component in an air cleaner that physically removes the pollutants from interior air.
Merv The Minimum Efficiency Reporting Value is the standard comparison of the efficiency of an air filter. The MERV scale ranges from 1 (least efficient) to 16 (most efficient), and measures a filter's ability remove particles from 3 to 10 microns in size.
Merv Rating Minimum Efficiency Reporting Value (MERV) is a measure of air filter effectiveness. The higher the MERV rating, the better the filter will trap foreign particulate.
Microchannel A microchannel coil is designed with small channels in the tubes to increase energy efficiency.
Net Metering Net metering is a service many utility companies provide to customers with solar panels. The solar power goes into the grid, and the homeowner may receive credit at full retail value.
Oil Furnace An oil furnace is a combustion heating system that uses oil for fuel.
Operating Cost The day-to-day cost of running your home comfort equipment, based on energy use.
Outdoor Coil See Condenser Coil.
Package Unit A package unit houses all the necessary heating and/or cooling components in a single cabinet.
Packaged Terminal Heat Pump A packaged terminal heat pump is similar to a through-the-wall PTAC, but utilizes a heat pump instead of only an air conditioner.
Payback Analysis Overall measure of the efficiency and value of your home comfort system. By combining your purchase price and ongoing operating costs, a payback analysis determines the number of years required before monthly energy savings offset the purchase price.
Pilot Light The pilot light on a combustion heating system is a small gas flame used to ignite the main burner.
Programmable Thermostat A programmable thermostat allows a homeowner to control and program their heating and air conditioning system.
Prop 65 Warning This product can expose you to chemicals including lead and lead compounds, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to
Psc Motor A permanent-split capacitor (PSC) motor is commonly used in HVAC blowers, fans, and air handling units.
Ptac A Packaged Terminal Air Conditioner (PTAC) is a self-contained air conditioning system installed through a wall, typically in an apartment or hotel.
Puron Refrigerant R-410A or Puron® Refrigerant is an environmentally sound refrigerant designed not to harm the earth's ozone layer. Federal law requires that all manufacturers phase out ozone depleting refrigerants in the next few years. Puron Refrigerant is approved by the US Environmental Protection Agency as a replacement from Freon 22.
Pv Module Photovoltaic (PV) modules convert solar energy into electricity.
Quietech QuieTech™ is a noise reduction system that provides comfortable heat while generating very little noise in the process.
R-22 Refrigerant R-22 is a single component HCFC refrigerant with low ozone depletion potential. It has long been used in a variety of air-conditioning and refrigeration applications in a variety of markets. Production of R-22 will cease in 2015 per the Montreal Protocol.
R-410a Refrigerant A non-ozone depleting refrigerant used in HVAC systems and approved to replace previous generation chemicals like R-22.
Radiant Floor A radiant floor system circulates hot fluid via subfloor channels to deliver even, powerful heating.
Reciprocating Compressor A type of compressor used in air conditioners that compresses refrigerant by using a type of "piston" action.
Reclaiming Returning used refrigerant to the manufacturer for disposal or reuse.
Recycling Removing, cleaning and reusing refrigerant.
Refrigerant Refrigerant is the chemical in an air conditioner coil that traps and moves heat throughout the system.
Refrigerant Lines Two copper lines that connect the Condenser (Outdoor) Coil to the Evaporator (Indoor) Coil.
Refrigeration Capacity A measure of the effective cooling capacity of a refrigerator, expressed in Btu per hour or in tons, where one (1) ton of capacity is equal to the heat required to melt 2,000 pounds of ice in 24 hours or 12,000 Btu per hour.
Room Air Conditioner Room air conditioners are compact, single-zone units designed for easy installation in a window or through the wall.
Rotary Compressor A rotary compressor uses a roller design to compress refrigerant in an HVAC system.
Scroll Compressor A specially designed compressor that works in a circular motion vs. an up and down piston action.
Seer The Seasonal Energy Efficiency Ratio is a measure of the cooling efficiency of your air conditioner or heat pump. The higher the SEER number, the more efficient the system is at converting electricity into cooling power.
Seer2 Short for Seasonal Energy Efficiency Ratio 2, SEER2 measures the efficiency of your air conditioning system over an entire cooling season. It contains standards that have been updated from SEER to make heating and cooling equipment more energy efficient. The higher the SEER2 rating on your HVAC system, the more energy efficient it is.
Setback Thermostat A state-of-the-art electronic thermostat with a built-in memory that can be programmed for different temperature settings at different times of the day.
Single Package Product One outdoor unit that contains both a heating and a cooling system.
Single-stage A single-stage operating system is the current industry standard in heat pump and air conditioner units.
Space Heater A movable or fixed heater used to heat individual rooms.
Specific Humidity The weight of water vapor per unit weight of dry air.
Split System Refers to an air conditioner or heat pump that has components in two locations. Usually, one part of the system is located inside (evaporator coil) and the other is located outside your home (condenser coil).
Static Pressure Condition that exists when an equal amount of air is supplied to and exhausted from a space. At static pressure, equilibrium has been reached.
Tankless Water Heater A water heater that heats water before it is directly distributed for end use as required; also known as an on-demand water heater.
Temperature Zones In HVAC, individual rooms or zones in a building where temperature is controlled separately from other rooms or zones.
Thermal Efficiency The thermal efficiency of a water heater is a measure of how much heat it can generate from a given amount of energy.
Thermidistat A thermidistat automatically adjusts an HVAC system to maintain a desired interior humidity.
Thermostat Unit that monitors and controls your HVAC system products.
Thermostatic Expansion Valve A thermostatic expansion valve (TXV) is precision device used to meter the flow of liquid refrigerant entering the evaporator at a rate that matches the amount of refrigerant being boiled off in the evaporator.
Ton A unit of measure for cooling capacity. 1 Ton = 12,000 BTU's per hour.
Total Home Comfort System The ultimate solution to providing you with consistent, customized home comfort, despite the ever-changing weather.
Truesense Dirty Filter Detection TrueSense™ dirty filter detection reminds you when it's time to change your media filter.
Two Stage Compressor Two Stage Compressors are capable of two levels of operation, a low stage and a high stage. Properly sized equipment will operate 80% of the time in low stage, enhancing efficiency and comfort with lower humidity levels and quieter operation. It's like getting two air conditioners or heat pumps in one system.
Two-stage Operation Two-stage operation provides superior efficiency and better long term performance than a single-stage system.
Txv A thermal expansion valve (TXV) measures the refrigerant flowing out of the evaporator and controls the refrigerant flowing into it.
Ul UL is an objective, non-profit organization that tests and rates electrical products for public safety.
Upflow A type of furnace that draws cool air from the bottom and blows the warmed air out the top into the duct work. This type of furnace is usually installed in a basement or an out-of-the-way closet.
Usgbc The United States Green Building Council is a nonprofit organization dedicated to sustainability-focused practices in the building industry.
Uv Light System Ultraviolet (UV) light systems neutralize and kill airborne pathogens.
Variable Speed Variable speed blower motors can manipulate airflow to improve comfort and efficiency.
Ventilator A ventilator captures heating or cooling energy from stale indoor air and transfers it to fresh incoming air.
Water Heater A water heater is a device that heats water for household use.
Weatherization In HVAC, caulking and weatherstripping to reduce air infiltration and exfiltration into/out of a building.
Weatherstripping A material used to seal gaps around windows and exterior doors.
Zoning A way to increase your home comfort and energy efficiency by controlling when and where heating and cooling occurs in a home. Programmable thermostats are used to control operating times of the equipment. Dampers are used to direct air flow to certain parts or "zones" of the home.