Common Air Conditioning Terms

At Sansone, we believe a little air conditioning know-how is important for every homeowner. That’s why we’ve compiled this list of air conditioning industry terms and definitions from around the web to better help you navigate our site, and get the most out of your home investment.

The following terms are just a start. As always, if you have any questions about your air conditioning system, contact us right away.


AC fan

These various fans are driven by an AC (alternating current) motor providing air movement in heating, cooling and ventilation systems.

Air conditioner

An air conditioner is an appliance, system, or mechanism designed to control temperature, humidity and air quality in a defined space.

Air Handling Unit (AHU)

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.


British Thermal Unit (BTU)

This is a measurement of heat energy. A single 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.


Central Air Conditioning

Central air conditioning is a system in which air is cooled at a central location and distributed to and from rooms by one or more fans, and ductwork.


Chlorofluorocarbons (CFCs) have been widely used as refrigerants. The manufacture and use of such compounds has been phased out and has been replaced with zero Ozone depleting products such as hydrofluorocarbons (HFCs).


This is the component providing heat transfer to air when mounted inside an air handling unit or ductwork. The term is normally associated with a fin and tube heat exchanger using refrigerant or water as the heat transfer medium.


A key component of the refrigeration system, raising the pressure (and hence temperature) of the refrigerant, and circulating it through a closed loop system.

Related blogs: How to Tell If Your Home AC Compressor is Bad


A vessel or an air cooled coil that removes the superheat of compression, condensing the refrigerant gas into a high pressure liquid.



The process of removing moisture from the air within a conditioned space to maintain the required humidity.


Ducts are used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air including supply air, return air, and exhaust air.


Evaporator Coil

The part of an air conditioner or heat pump that absorbs the heat from the air in your house. It is located inside the air handler or attached to the furnace.

Related blogs: What to Do When Your Evaporator Coil is Leaking


Fan Coil Unit

A fan coil unit (FCU) is normally a chilled water device consisting of a heating and/or cooling coil, fan, valve(s) and a local controller. It forms part of a larger HVAC system found in residential, commercial, and industrial buildings.


Gauge Pressure

The reading taken from a gauge normally zeroed at atmospheric pressure (one bar absolute or 14.7 psi) so that pressures can also be read as a negative when below atmospheric pressure. (Often referred to with “g” on the end – e.g. Barg, Psig).


Heat Pump

A heat pump is a mechanical device that absorbs low grade heat from a lower temperature location and upgrades and transfers this higher temperature (created by mechanical work), to heat a space to a sufficient comfort level. Heat pumps may be air to air, air to water, water to water or ground to water.


The process of adding moisture to the air within a space.


HVAC (heating, ventilation, and air conditioning) is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality.


MERV Rating

The Minimum Efficiency Reporting Value (MERV) rating is used to rank the efficiency of air filters. Every air filter has holes that allow air and particles to pass through. The smaller the holes, the fewer particles that can pass through. Higher MERV ratings indicate smaller holes, and therefore a more efficient filter.


Natural Refrigerant

Natural refrigerants are non-fluorochemical refrigerants, such as ammonia (R717), carbon dioxide (R744) and hydrocarbons such as propane (R290) or isobutene (R600a). These products exist naturally in the environment. An alternative to fluorochemical refrigerants, often used due to their low direct GWP and ODP potential. (However it should be noted that commercial production of natural refrigerants is normally via man-made synthesis).



The fluid used for the heat transfer within a refrigeration system. The refrigerant absorbs heat at low temperature and pressure, and transfers heat at high temperature and pressure. The refrigerant can be many materials, commonly fluorocarbon compounds, but also natural refrigerants such as ammonia, CO2, hydrocarbons as well as other compounds, such as water and air.


Split System

A split air conditioning system consists of two main parts: the outdoor (condensing) unit and the indoor unit. Although any size of unit could be defined as a split system it normally refers to smaller equipment, specifically air to air heat pumps.



A device that automatically regulates temperature, or that activates a device when the temperature reaches a certain point.

Have a Question?

At Sansone, we want you to get the most out of your investment. Whether you have an AC-related question or need services, we’re here to help. Call our technicians today to schedule your next appointment or reach out to us online.
Broward: (954) 800-2858
Palm Beach: (561) 701-8274
St. Lucie: (772) 879-5656

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