Common HVAC Terms

Popular Words in the HVAC Industry

HVAC terms

In the HVAC industry, we use a lot of terms that describe heating, cooling, system components, and more. As someone not in the HVAC industry, it may be hard to understand what they all mean, so we put together a list of common terms for you:


The way in which air currents move. Airflow usually refers to how freely air can move throughout a home.


British Thermal Unit, which refers to the amount of heat required to raise the temperature of one pound of water.

Central Air

A type of HVAC unit that heats or cools air at a main location, then distributes it throughout your home (as opposed to a room air conditioner or heater, which only heats or cools that room).


A component that is responsible for pumping refrigerant. Compressors are found in outdoor heat pumps or air conditioners.

Condenser Coil

A component that is responsible for collecting or producing heat. Condenser coils are also found in outdoor heat pumps or air conditioners and their job is based on the outside temperature.


A movable plate or gate that increases or decreases airflow in the ductwork.


The pathway of vents throughout your home that work with central air units to carry warm or cold air to each room.

Evaporator Coil

A component that is responsible for absorbing excess heat in your home. Evaporator coils are found in heat pumps or air conditioners.

Fan Coil Unit

A small unit often used in (hotels or apartments) that houses only a blower and a heating and/or cooling coil.


The part of an HVAC unit that warms the air before it flows through the ductwork in your home.

Geothermal HVAC

A type of HVAC unit that is located under the ground and uses the temperature of the earth to create energy. Geothermal units use special loops to transfer heat and heat or cool your home.

Heat Exchanger

A component that is responsible for warming the air before it’s distributed throughout your home ductwork. Heat exchangers are found in furnaces.

Heat Gain/Loss

Refers to the amount of cooling (heat gan) or heating (heat loss) needed to maintain a certain temperature or humidity.

Heat Pump

A type of HVAC unit that either removes heat or added heat to your home in order to maintain a certain temperature.


A system that regulates the amount of moisture in the air. The right amount of moisture can improve breathing, reduce symptoms of asthma, help prevent illnesses, and more.

Programmable Thermostat

An “after-market” thermostat that can automatically regulate the temperature of your home based on programmed settings.


The emission of electromagnetic waves or moving subatomic particles. Radiation is how radiators produce heat.


A fluid used in HVAC units that transforms from a liquid to a gas and back. The refrigerant produces a cooling effect as it transforms and helps heat or cool the air.

Refrigerant Lines

Found in an air conditioner or heat pump, refrigerant lines are copper lines that connect the outdoor unit to the indoor evaporator coil.


When liquid refrigerant is colder than the temperature needed for it to stay liquid (and not boil.) Can take place in heat exchangers or outside of them.


A unit used to measure the cooling capacity of an air conditioning system. The term is based on the amount of heat needed to melt 2,000 pounds (one ton) in a 24-hour period.


An application for homes or buildings that lets you independently control the temperature of specific rooms.

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