HVAC Glossary

This glossary of HVAC terms will help you to better understand your heating and air conditioning system.

A system or an assembly comprised of components designed to control air temperature, relative humidity and air flow.

A type of air conditioning system that uses air R-22 or R-410A refrigerant as a condensing medium. The condenser usually is located outside and the refrigerant is piped to it from the indoor unit. That way, heat is transferred to the outside air.

The air conditioning component that moves heated or cooled air throughout a home's ducts. The air is typically located indoors and includes a blower, dampers and other equipment in direct contact with air flow.

The amount of refrigerant in a system.

Equipment that enables heat transfer to and from the refrigerant and the air when installed inside an air handling unit.

The pump that circulates vapor refrigerant throughout the system from the indoor evaporator to the outdoor condenser, and back again.

A series of tubes filled with refrigerant that carries heat from the home and removes it outdoors, thereby allowing the refrigerant to condense or liquefy.

A device that condenses a substance from a gaseous to a liquid state, typically by cooling it.

Any pipe or closed chamber, usually made of sheet metal or fiberglass, used to house and conduct air flow from an air handling unit to the conditioned space.

A type of air conditioning system that does not use ducts to transfer cool. Instead, the outdoor condenser unit is connected directly to an interior air handler. Because of this direct connection, generally only one room or space can be cooled at a time making ductless mini-splits a viable option for room additions or add-ons.

A heating solution that combines a furnace and a heat pump to provide an economical way to heat a home. A heat pump is activated for moderate heating needs and a furnace is switched on when higher levels of heat are needed. This system helps maximize the energy efficiency of each unit.

A ratio to determine the energy efficiency of an air conditioner. The higher the EER rating, the more efficient the unit. EER ratings are generally lower than SEER ratings because SEER ratings are seasonally adjusted while EER ratings are calculated against a fixed temperature.

A series of tubes filled with liquid refrigerant that absorb heat from the air as the liquid refrigerant is evaporated into vapor.

An opening through which outdoor air is drawn into a system.

The HVAC component that adds heat to indoor air by burning fuel in a heat exchanger.

An air conditioner that has a reversing valve allowing it to alternate between heating in the winter and cooling in the summer.

A measure of the amount of moisture in the air.

A measure to determine heat gain and loss within a structure so that properly sized HVAC equipment can be installed.

A measure of the value of your system that determines the number of months required before monthly energy cost savings offset the initial investment.

An HCFC (hydro chlorofluorocarbon) refrigerant, often referred to by a brand name such as Freon®, used primarily in residential air conditioning systems. It is being phased out for its higher global warming potential (GWP) and ozone depleting properties. R-22 is no longer included in new air conditioning systems.

A non-ozone depleting refrigerant that has replaced R-22 as the preferred refrigerant of choice in the U.S., Japan and Europe.

A grille and damper assembly that covers the opening or end of an air duct.

The ratio of the amount of moisture in the air compared to the amount of moisture the air could hold at the current temperature, expressed as a percentage.

The air drawn into the heating unit after having been circulated through a room.

A rating that expresses the efficiency of air conditioning equipment throughout an entire average cooling season, including both the hottest and coolest days. It stands for Seasonal Energy Efficiency Ratio. The higher the SEER rating, the more efficient the system.

The most common type of residential system, it consists of two main components – a compressor and condensing unit installed outdoors, and an air-handler installed indoors.

A unit of measure used to describe the cooling capacity of an air conditioning system. One ton of cooling is the amount of heat needed to melt a one ton block of ice in a 24 hour period.

A method of providing independent heating or cooling to different areas or rooms, typically controlled by separate thermostats.

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