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What does that Mean?! – The HVAC Glossary

HVAC-glossaryHave you called your heating and cooling professional and they asked you to locate the air handler on your air conditioner? What if they asked you the SEER of your heat pump?

 At Allstar Heating and Cooling, we strive to do everything we can to help our customers make informed decisions about maintenance and service repair. Because we want you to receive the best service possible, we’ve compiled a list of common HVAC terms:


Air handler – the air handler is the term for the blower fan and heat transfer coil, as well as the housing of those components.

Attic fan – an attic fan is a fan mounted on your attic wall that exhausts warm attic air to the outside.

Attic vent – your attic vent is a mechanical device used to ventilate an attic space, primarily to reduce heat buildup and moisture condensation.

Blower fan – the blower fan moves air from the return duct over the coil / heat exchanger. The circulated air is then heated or cooled and sent through the supply duct, past the dampers and into your home.

British thermal unit (BTU) – most furnaces and heating systems measure their heating output in terms of BTUs. One BTU is the amount of heat required to raise the temperature of one lb of water by one degree – this is equal to 252 calories.

Compressor – this is the outdoor unit on a split system air conditioner. The compressor puts pressure on the refrigerant in the air conditioner so that it can flow through the system.

Condenser – the condenser is a device in an air conditioner or heat pump where the refrigerant condenses from a gas into a liquid when it is depressurized or cooled.

Duct fan – a fan that helps blow air through your ducts. That one was easy.

Ducts – round or rectangular tubes, usually made of sheet metal, fiberglass board or a flexible plastic / wire composite. Your ducts carry the conditioned air through your home.

Forced air HVAC system – any HVAC system that uses a fan to blow conditioned air through air channels or ducts.

Fuel efficiency – this refers to the amount of heat produced by your heating system vs. how much fuel you burn.

HEPA filters – High Efficiency Particulate Arrestance filters. HEPA filters are the most effective air filters available and are commonly found in high-end air cleaners.

Return air – “used” air that is returning to your HVAC system to be reconditioned.

Return duct – a duct through which return air goes to be cycled back through your HVAC system.

Seasonal energy efficiency ratio (SEER) – a measure of efficiency for air conditioners and heat pumps. Specifically, the average BTUs of cooling delivered for every watt-hour of electricity used.

Split system air conditioner – an air conditioner that houses the different components in separate units.


We hope that you will find this glossary helpful and make any HVAC service needs less intimidating. If you have any questions or would like more information about air conditioner maintenance, contact your local experts at Allstar Heating & Cooling today at 262-361-3900.


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All Star Heating & Cooling

Preserving, Protecting and Defending Your Comfort Since 1904

Proudly serving Hartland, Waukesha and surrounding areas.