HVAC Terms

Below Are Some Of The Most Common HVAC Industry Terms For Your Reference


Air Conditioning Contractors of America – www.acca.org

AFUE (Annual Fuel Utilization Efficiency)

A measurement used to rate furnace efficiencies by dividing the ratio of heat output by heat input.

Air Conditioner

Assembly of equipment that changes humidity levels, temperature or quality of air.

Airflow Volume

Measured in cubic feet per minute (cfm), this is the amount of air circulated in a space.

Air Handler

Parts of a system including the fan-blower, filter and housing.


Air Conditioning, Heating and Refrigeration Institute


American Society of Heating, Refrigeration and Air Conditioning Engineers


British Thermal Unit. Measures the amount of heat required to raise or lower the temperature of one pound of water one degree Fahrenheit.


The number of BTU’s per hour


The device that facilitates the combustion of air and gas.


HVAC capacity is the output produced by the heating or cooling unit and is measured in BTUs per hour.

CFM (Cubic Feet per Minute)

A measurement of airflow volume.

Charging a System

Adding coolant, or refrigerant, to an HVAC system.


A pump that increases the pressure of gas.


Vapor that is turned into a liquid as its temperature is lowered.

Condenser Coil

Also an outdoor coil. A device that removes heat from the refrigerant allowing the refrigerant to be converted from gas to liquid.

Condenser Fan

A fan that passes air over the condenser coil to facilitate the removal of heat from the refrigerant.


Found at the exit point of ductwork, this plate usually contains grates that can be opened or closed to control the flow of air into a zone.


A device that removes humidity, or moisture, from the air.


A grille over an air supply duct with vanes that distribute the discharging air in a specific pattern or direction.


Department of Energy

Downflow Furnace

A furnace with an intake on the top and an air discharge at the bottom.

Drain Pan

Also a condensate pan. As the refrigerant vapor is liquefied, the drain pan collects the condensate and funnels it to the drain line.

Dry Bulb Temperature

The temperature as measured without the consideration of humidity.


A network of metal, or flexible material flowing throughout a space which delivers air from an HVAC unit to the respective areas of a home or office.


Energy Efficiency Ratio


Environmental Protection Agency

Expansion Valve

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

Evaporator Coil

Also an indoor coil. A device that is designed to absorb heat in the air in order to change the liquid refrigerant that flows through it into a vapor.


A temperature scale in which water freezes at 32 degrees and boils at 212 degrees at normal atmospheric pressure.


A device that creates airflow.


A device that acts like a strainer to remove dirt or undesired particles.


A vent that removes the byproducts of combustion from a furnace.


The major component in heating a home. A device that facilitates the combustion of fuel and air to create heat.


A delicate metal strip connecting two parts of an electrical circuit. This strip breaks, or melts, in the event of excess electrical charge, breaking the electrical circuit.

Heat Exchanger

A device through which heat is transferred to a cold area or surface.

Heat Gain

The amount of heat added or created in a designated area.

Heating Coil

A coil that acts as a heat source for a heating system.

Heat Loss

The amount of heat subtracted from a designated area.

Heat Pump

A device used for either the heating or cooling of a space by transferring heat between two reservoirs.

HSPF (Heating Seasonal Performance Factor)

This factor rates the efficiency of the heating portion of the heat pump.


A device that adds humidity, or moisture, to the air.


The device that measures humidity and turns the humidifier on and off.


Dampness in the air caused by water vapor.


Heating, Ventilation and Air Conditioning


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


Protective material that slows down the transfer of heat.

Kilowatt (kW)

1,000 watts.

Latent Heat

A type of heat that when added to an area produces an effect other than an increase in temperature.


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


North American Technician Excellence – Leading Certification in the HVAC industry.

Package Unit

A heating and cooling system contained in one outdoor unit.


Pounds per square inch.


Polyvinyl chloride; a type of plastic.


A chemical that condenses from a vapor to liquid and, in the process, decreases in temperature.

Refrigerant Charge

The amount of refrigerant in a system.

SEER (Seasonal Energy Efficiency Ratio)

A rating system developed by the U.S. Government to indicate the efficiency level of cooling equipment.

Sensible Heat

Heat added or subtracted that causes a change in temperature.

Supercooled Liquid

Liquid refrigerant cooled below its saturation point.


Creating a drop in temperature by removing sensible heat from a refrigerant liquid.

Superheated vapor

Refrigerant vapor heated beyond its saturation point.


Creating a rise in temperature by adding heat energy to a refrigeration vapor.


Sensors that monitor and control the output of an HVAC system.

Thermostatic Expansion Valve

A device that creates a constant evaporator temperature.


The unit of measurement for air conditioning system capacity. One ton of air conditioning removes 12,000 Btu’s of heat per hour from a home. Residential homes air conditioning systems usually range from 1 to 5 tons.

Upflow Furnace

A furnace that pulls in air from the bottom or side and releases it through the top.


A space where the pressure is significantly below that of standard atmospheric pressure.


A unit of electro-motive force.


The force pushing electrical current along wires and cables.


The unit of electrical power equal to the flow of one amp at a potential difference of one volt.


A system that divides a home, office or space into different regions in order to better control the temperature and effectiveness of a heating and cooling system.