HVAC Glossary

A major trade association for the HVAC industry, the Air Conditioning Contractors of America.

The number of times per hour a room’s air is replaced through ventilation.

An appliance designed to dehumidify and extract heat from a home or office, leaving the remaining air cooler.

The volume of air your duct system moves. In general, air conditioners are designed to move about 400 cubic feet per minute (cfm) for each ton of air conditioner capacity.

A large metal box, part of the indoor unit for a furnace/AC system that contains the blower and heating or cooling elements.

The thermal efficiency measure of space-heating furnaces and boilers, expressed as a percentage.

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers.

The outdoor temperature at which a heat pump’s output matches heating needs.

The section of shaped sheet metal that transitions the duct on one end to the grille or register on the other end.

One BTU is the energy required to raise one pound of water one degree Fahrenheit.

Also known as a ‘run capacitor’, it gives an air conditioning system the initial boost it needs to turn on and also provides continuous power.

Measuring the pressure of the refrigerant of an AC system to determine if it contains the proper amount.

Part of the air conditioner that performs heat transfer to air, mounted inside an air handler or ductwork.

A device that raises the temperature and pressure of the refrigerant in an air conditioning system.

A heat exchanger that removes heat from the HVAC system. The condenser is the ‘hot’ side of an air conditioner or heat pump.

The part of an HVAC system that controls all or part of the system, usually based on input from a thermostat.

Measurement of the change (delta) of the temperature of air moving through the evaporator coil.

A certification required by the Environmental Protection Agency (EPA) for HVAC technicians to be able to handlle refrigerants.

Part of the basic refrigeration cycle that absorbs or adds heat to the system, usually to absorb heat from the air.

Part of an HVAC system that adds heat to the air of a home.

Register used primarily in return air vents that doesn’t contain any moving parts.

Part of an HVAC system that transfers heat from the hot parts of the system to the cold parts.

Moves heat from inside to outside in the summer months and from outside to inside in winter.

A source from which heat is collected, such as outdoor air for heat pumps.

Based on the AFUE rating of a furnace, usually referring to a 90% or higher efficiency furnace.

A device that controls indoor humidity levels by adjusting moisture in the air.

Abbreviation for Heating, Ventilation, and Air Conditioning.

Heat that must be removed from the air to remove moisture.

Tubing that connects the condensing unit to the evaporator coil of an air conditioner.

Determining the correct HVAC system size for a home based on heat gain/loss.

The process of determining the proper size of an air conditioner and/or furnace for a home.

More efficient air filters for an HVAC system, constructed of materials that catch smaller particles.

A rating for filters used in HVAC systems. The higher the MERV rating, the more particles it catches.

North American Technician Excellence, a certification for HVAC professionals.

The sheet metal box connected to either side of an HVAC system’s air handler.

The coolant that enables modern air conditioning systems to remove heat from the home.

The cycle that allows an air conditioner to transfer heat from inside and send it outside.

Cover for a heating or air conditioner grate inside a home, usually with movable louvers.

The section of an HVAC ductwork system that returns air from the house back to the air handler.

Seasonal Energy Efficiency Ratio, measuring air conditioning and heat pump cooling efficiency.

An air conditioning system with an indoor unit and an outdoor condensing unit.

Refers to an AFUE rating of a furnace, typically in the 80% range.

The pressure inside a home’s ductwork system, affecting HVAC efficiency.

Auxiliary or emergency heat used when temperatures drop below a heat pump’s balance point.

The part of a home’s duct system that moves conditioned air into the living space.

A device that monitors and regulates an HVAC system.

The capacity of an air conditioning system. One ton equals 12,000 BTU/hour.

A large piece of ductwork that attaches directly to the plenum and distributes air.

An air conditioning system with high and low settings for efficiency.

HVAC motors that adjust speeds for improved energy efficiency and comfort.

Divides a home into sections that can be controlled independently for comfort.