hvac-r terminology
HVACR Terminology

Understanding heating ventilation, air conditioning and refrigeration (HVAC-R) systems and learning some terms will help you better communicate with a HVAC-R technician about the problems of your HVAC-R systems.

When you understand some HVAC-R terms you also know why and how to do some common maintenance. Another benefit is avoiding some HVAC-R technicians cheat on you for some components/parts.

In this part some common used terms in HVAC-R trade are listed here, that you might hear from a HVAC-R technician when you make a service call.

Frequently Asked Questions

BTU is a measurement of the amount of heat required to raise or lower the temperature of one pound of water one degree Fahrenheit.

PSI, pounds per square inch (PSI), is a widely used British and American unit of measure for pressure. It is a unit of pressure resulting from the force of one pound-force applied to an area of one square inch.

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


accumulator — A device installed in the suction line of an air conditioner to prevent liquids from entering the compressor.

air balance — A term describing the distribution of air in an HVAC system. A balanced system has enough air distributed to match the amount required by all parts of the system at any given time.

air changes per hour — The number of times the entire volume of air in a building is replaced via natural ventilation or air conditioning during one hour.

air diffuser — A distribution point where conditioned air is mixed with room air. Typically these are covered with some type of grille and located in the floor or ceiling.

air exchange rate — A measure of how quickly the air indoors is replaced by outside or conditioned air. The air exchange rate is often measured in air changes per hour.

air flow — The free movement of air.

air flow volume — The amount of air your air conditioner circulates through your home, typically measured in cubic feet per minute.

air handler — A moving part inside your home that propels air through the ductwork. A furnace or blower coil often serves this function.

air handling unit — See Air Handler.

air infiltration — The unintended entrance of air into a space via leakage, temperature differentials or wind.

air passages — Spaces through or within walls, floors and ceilings that allow conditioned air to move out of the structure.

all-in-one system — See Packaged Unit.

ambient air — Outdoor, unconditioned air.