The HVAC industry uses terms and vocabulary that may not be easily understood by the average homeowner. In fact, there are probably a lot of people who don’t even know that HVAC itself stands for Heating, Air Conditioning, and Ventilation. This glossary list will help you understand are some of the more common HVAC terms used regularly in the industry so you can become more educated about the heating and cooling system in your home.

HVAC Terms Glossary

The following HVAC terms include common acronyms, units of measure, and types of equipment used in the heating and cooling industry.

ACH – An acronym for Air Changes Per Hour, which refers to how many times each hour a room receives air or has air removed via ventilation.

AFUE – An acronym for Annual Fuel Utilization Efficiency. It measures how efficiently your furnace can use fuel. 

Air cleaner (air purifier) – An installed system that removes allergens and other particles out of the heated or cooled indoor air. 

Air handler – An indoor unit that can be installed to push heated and cooled air through the home’s ductwork. Air handlers are typically paired with heat pump systems or air conditioners.

Blower – The component in a forced air heating and cooling system that circulates conditioned air from the furnace or air handler through the ductwork into the home. The blower assembly includes the blower motor and blower fan.

BTU – A term used to define heating capacity of a furnace or the amount of heat an air conditioner can extract from a space. BTU stands for British Thermal Unit, and is the amount of heat required to raise a pound of water by one degree Fahrenheit. Another common term, BTU/H stands for British Thermal Units per Hour.

Burner – A furnace component that combusts air and gas.

Capacitor – The run capacitor provides extra energy to the condenser fan motor and blower motor when they are in operation.

Capacity – A heating or cooling unit’s ability to heat or remove heat from a specified space. For heating systems, capacity is typically stated in BTUs, and cooling system capacity is stated in tons.

Charging – A term for adding refrigerant to an HVAC unit.

Compressor – A part of the air conditioner or heat pump that is located in the outdoor unit. It compresses, circulates, and pumps refrigerant to cool the air.

Condensate – Moisture that is pulled from the air as air makes contact with the evaporator coil in a cooling system, or the combustion byproducts that condense in a condensing furnace and are expelled as a liquid. Condensate is drained out of the system via the condensate pan and drain line.

Condenser coil – (outdoor coil) The outdoor part of the heat pump or air conditioner that releases or collects heat.

Condensing unit – The outdoor equipment that consists of the compressor, condenser coils, a fan motor, and their controls.

Damper – Plates that can be adjusted to restrict air flow in the ductwork.

Dehumidifier – A device that cools air to condense moisture vapor into a liquid in order to reduce airborne humidity levels.

Downflow – A furnace that takes in cool air at the top of the unit and blows out warm air from the bottom. This type of furnace is commonly used for installations on the second floor of a home.

Dry bulb temperature – Temperature when measured without considering humidity levels.

Ductwork – The distribution system for a forced air heating and cooling system which transports conditioned air from the furnace or air handler into the home.

EER – An acronym for Energy Efficiency Ratio, which represents a cooling unit’s output of cooling energy in BTUs to its intake of electricity at a given point.

ENERGY STAR® – HVAC products that meet or exceed EPA guidelines for high efficiency.

Evaporator Coil – The part of the air conditioner or heat pump that is located indoors and attaches to the furnace or inside the air handler. Refrigerant flowing through the coil absorbs or releases heat, changing in state between liquid and gas. Sometimes known as the indoor coil.

Fan coil – An indoor unit installed with an air conditioner or heat pump which changes refrigerant from gas to liquid and circulates air over the coil.

Filter – A component that filters contaminants from the air moving through the HVAC system to keep particulate matter out of the unit.

Flue – A vent pipe that allows a furnace’s combustion byproducts to safely exit the home and system.

Fresh air intake – An opening which allows outside air to be drawn into the home or HVAC system.

Heat Exchanger – Located inside the furnace, it transfers heat to air.

Heat Pump – An HVAC unit that heats or cools by moving heat. It removes heat from the indoors in the summer, and reverses to bring heat inside from the outdoors in the winter.

HSPF – HSPF stands for Heating Seasonal Performance Factor, and is used to measure the heating efficiency of a heat pump.

Humidifier – A device that adds water vapor or steam to circulating air in order to increase airborne humidity in a home.

Humidistat – A control that measures airborne humidity and operates the humidifier.

HVAC – Abbreviation for Heating, Air Conditioning, and Ventilation.

Hybrid system – A type of HVAC system that combines two different types of equipment and allows the most energy efficient option to operate for the present conditions.

IAQ – An acronym that stands for Indoor Air Quality.

Matched system – Indoor and outdoor units that are designed to work together and offer the specified energy efficiency levels.

MERV Rating – This acronym stands for Minimum Efficiency Reporting Value and refers to the size of the holes in a filter that air can pass through. Higher MERV ratings mean smaller holes in the filter that can trap more particles. 

NATE – North American Technician Excellence – The only certification program for HVAC professionals that is supported by the entire industry. NATE certification is a useful place to start to help determine which HVAC technician to choose for the job.

Packaged unit – A type of HVAC system that contains all system equipment in one cabinet.

Plenum – A component that connects the HVAC equipment and ductwork. A supply plenum moves conditioned air from the unit to the duct system, and a return plenum takes in return air from the ducts and sends it into the HVAC unit.

R-22 – A refrigerant (also known as Freon) that is found in older air conditioning and heat pump systems. Since it depletes the ozone layer, R-22 has been banned for use in any HVAC equipment manufactured after January 1, 2010; after 2020, manufacturers will no longer be able to produce R-22 for use with heat pumps and air conditioners. 

R-410A – A hydrofluorocarbon refrigerant that does not deplete the Earth’s ozone layer. Also known as Puron, this refrigerant is an alternative to R-22 and is used in the manufacture of new cooling equipment.

Refrigerant – A chemical substance used with most air conditioning units that helps cool the air.

Refrigerant charge – The amount of refrigerant within an HVAC unit.

Thermostat – A mechanism that detects temperature levels to activate and shut off your furnace or air conditioner. 

SEER – An acronym for Seasonal Energy Efficiency Ratio, which rates energy performance of an air conditioner or heat pump. A high SEER rating means higher energy performance and savings.

Split system – An HVAC system that has equipment located indoors and outdoors. Central air conditioning systems and heat pump systems are split systems, composed of an outdoor condensing unit and indoor air handler or furnace.

Ton – The measure used to reflect the cooling capacity of an air conditioner. 1 ton is equal to 12,000 BTU/H.

Upflow – A furnace that pulls in cool air from the bottom of the unit and blows warm air out its top. These furnaces are typically installed in basement applications.

Ventilation – Changing air in and out of an interior area via natural or mechanical methods.

Zones – Refers to separate rooms or areas in the home. Zoning systems can be installed with HVAC equipment to allow for separate heating, cooling, and humidity control in different areas of your house. Zoning systems use individual thermostats and dampers in the duct-work to direct heating and cooling where needed.

HVAC Services in Indiana

We hope that the above glossary of HVAC terms will help you better understand your home’s heating and cooling system. Knowing these HVAC terms will also help you communicate accurately with your HVAC technician during service calls. To schedule HVAC service for your home, call Star Heating & Cooling today.