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HVAC Glossary


Air Conditioner – An appliance, system, or mechanism designed to dehumidify and extract heat from an area. Usually this term is reserved for smaller self contained units such as a residential system. Comfort Solutions HVAC for are cooling specialists.

Air Handler – An air handler, or air handling unit, is the indoor part of an air conditioner or heat pump that moves cooled or heated air throughout the ductwork of your home. It is usually a large metal box containing important elements of an HVAC system that controls airflow and filtration.


British Thermal Unit (BTU) – A measurement of heat energy. One Btu is the amount of heat required to raise one pound of water by one degree Fahrenheit. The higher the Btu rating, the greater the heating capacity of the system.


Coil – Equipment that performs heat transfer to air when mounted inside an air handling unit or ductwork. It is heated or cooled by electrical means or by circulating liquid or steam within it.

Compressor – An AC or heat pump compressor is the part of an outdoor air conditioner or heat pump that compresses and pumps refrigerant to meet household cooling requirements.

Condenser – A condenser (or AC condenser) is the outdoor portion of an air conditioner or heat pump that either releases or collects heat, depending on the time of the year.


Damper – Found in ductwork, this movable plate opens and closes to control airflow. Dampers are used effectively in zoning to regulate airflow to certain rooms.

Dual Fuel System – A heating solution that combines a furnace and a heat pump to provide an economical way to heat a home.  A heat pump is activated for moderate heating needs and a furnace is switched on when higher levels of heat are needed. This system helps maximize the energy efficiency of each unit.

Duct – Any pipe or closed chamber, usually made of sheet metal or fiberglass, that is used for housing and conducting air flow from an air handling unit to the conditioned space.


EER (Energy Efficiency Ratio) – A ratio to determine the energy efficiency of an air conditioner. The higher the EER rating, the more efficient the unit. EER ratings are generally lower than SEER ratings because SEER ratings are seasonally adjusted while EER ratings are calculated against a fixed ambient temperature.

Evaporator Coil – A series of tubes filled with liquid refrigerant that absorb heat from the air as the liquid refrigerant is ‘evaporated’ into vapor.


Furnace – An indoor heating unit that works in conjunction with an air conditioner or heat pump.  Learn more about the heating services Comfort Solutions HVAC provides.


Gas Furnace – A gas furnace is the part of an HVAC system that converts natural gas or propane into high-temperate heat for the home.


Heat Pump – A heat pump is an HVAC unit that heats or cools by moving heat. During the winter, a heat pump draws heat from outdoor air and circulates it through a home’s air ducts. In the summer, it reverses the process and removes heat from the house and releases it outdoors.

Humidifier – A humidifier is a device that adds moisture to indoor air in a single room or throughout an entire house. Whole-home humidifiers may use the fan in your furnace or air handler to blow humidified air throughout the ductwork, or they may work independently of your heating and cooling system to maintain humidity levels even when the furnace or air handler isn’t operating.

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

HVAC – Term used for heating, ventilation and air conditioning.


Ignition – Elevating the temperature of a substance to the point of causing a combustive reaction.


Kilowatt (kW) – 1,000 watts of electrical power.


Latent Heat – Is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process that creates a change of state. An example is the latent heat of evaporation which creates a phase transition from liquid to a vapor at a specified temperature and pressure.


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


NEMA – National Electrical Manufacturing Association


Outside Air Temperature – A measure of the air temperature outside a building. The temperature and humidity of air inside and outside the building are used in enthalpy calculations to determine when outside air can be used for free heating or cooling. Abbreviated OAT.


Particulates – The fine liquid or solid particles contained in combustion gases. The quantity and size of particulates emitted by cars, power and industrial plants, wood stoves, etc are regulated by the U.S. Environmental Protection Agency.

Programmable Thermostat – A type of thermostat that allows the user to program into the devices’ memory a pre-set schedule of times and temperatures enabling or disabling the HVAC equipment.

PSI – A pound per square inch is a unit of pressure resulting from the force of one pound-force applied to an area of one square inch.


Radiant Floor – A type of radiant heating system where the building floor contains channels or tubes through which hot fluids such as air or water are circulated.

Refrigerant – The compound (working fluid) used in air conditioners, heat pumps, and refrigerators to transfer heat into or out of an interior space. This fluid boils at a very low temperature enabling it to exude and absorb heat.

Refrigerant Charge – The amount of refrigerant in a system.

R-22 – An HCFC (hydro chlorofluorocarbon) refrigerant, often referred to by a brand name such as Freon®, used primarily in residential air conditioning systems. It is being phased out for its higher global warming potential (GWP) and ozone depleting properties.


SEER – The efficiency of air conditioners is often rated by the Seasonal Energy Efficiency Ratio which is defined by the Air Conditioning, Heating, and Refrigeration Institute as the cooling output during a typical cooling-season divided by the total electric energy input during the same period. Learn more about SEER ratings in this blog post by Comfort Solutions HVAC.

Sensor – A device that reacts to a change in conditions.

Split System – An outdoor unit combined with an indoor unit (as opposed to a package unit), generally providing more efficiency and configuration options.


Thermostat – A wall mounted device that monitor and controls the output of an HVAC system.

Ton – One ton is 12,000 BTUs per hour.


Ventilation – The process of moving air (changing) into and out of an interior space either by mechanically induced (forced) means.

Volt – Is the derived unit for electrical potential and electromotive force.

Voltage – The force pushing electrical current along wires and cables.


Watt – Is defined as joule per second and can be used to express the rate of energy transformation with respect to time.


Zoning – A way to increase your comfort and energy efficiency by controlling when and where heating and cooling occurs. Programmable thermostats are used to control operating times of the equipment. Dampers are used to direct air flow to certain parts or “zones”.

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