A Glossary of HVAC Terms A-Z to Help You in School and in Your Career

hvac glossary of terms

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Planning a career in the heating, ventilation, air conditioning and refrigeration field? Get ready to memorize words, acronyms and their meanings. A lot of them.

HVAC training teaches all of the essential HVAC terminology, of course, but learning how to speak the language ahead of time will help you when terms like BTUH and SEER start flying around the classroom.

We’ve compiled a glossary of HVAC terms to help you tell your AOHs apart from your CAEs. Let’s dive in.


This is the abbreviation for Annualized Fuel Utilization Efficiency, which is the fuel efficiency rating for furnaces that are less than 150,000 BTUH (more on that later) and are powered by oil, gas or warm air.

(AHRI) Air Conditioning, Heating and Refrigeration Institute

ARI is an industry association that develops the standards for measuring and certifying product performance.

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Air Handler

The air handler is also known as a coil blower. It’s the indoor component of an air conditioning unit or heat pump that blows cooled or heated air through the ductwork of a home.

All-in-One System

An all-in-one system is a heating and air conditioning system where the parts are found in one cabinet and the unit is usually installed beside or on top of a home.


AOH is the abbreviation for Annual Operating Hours, which is the total allowance of full- and part-load operating hours in any given geographical location.


BTU is the abbreviation for British Thermal Unit, which is a unit of heat energy. One BTU of heat is what is needed to raise one pound of water by one degree Fahrenheit. The higher the BTU rating is, the more heating capacity the system will have.


BTUH is the abbreviation for British Thermal Units Per Hour.


CAE is the abbreviation for Combined Annual Efficiency, which is the measure of the amount of heat made for every dollar of fuel used, which includes both home and water heating systems.


The capacity is the producing capability of a heating or cooling system. With heating, it’s generally measured in BTUs. For cooling, it’s typically measured in tons.


CFM is the abbreviation for Cubic Feet Per Minute. This is how the amount of airflow is measured.


The compressor is the part of the outdoor AC unit or heat pump that compresses the air and pumps enough refrigerant to meet the cooling requirements.

Condenser Coil

The condenser coil is the exterior part of an air conditioner or heat pump that either releases or accumulates heat, which is determined by time of the year.


Cycling is the turning on and off of an HVAC system.


The damper is a movable part in a system’s ductwork that regulates the airflow. They are also used to redirect the air to a specific spot.


Ductwork is usually a tube or square channel by which air is moved through various rooms. Green ductwork is getting popular with homeowners because of its energy-efficient and environmentally friendly qualities.

Energy Star

Energy Star is a program developed by the Environmental Protection Agency (EPA) to help reduce energy consumption. The EPA issues energy efficiency ratings for HVAC systems.  An Energy Star label indicates whether the appliance meets or exceeds the EPA guidelines for energy efficiency.


EPA is the abbreviation for the Environmental Protection Agency. This government branch develops and enforces federal environmental regulations in the United States.

Evaporator Coil

The evaporator coil is located inside the air handler. Its primary function is to absorb the heat from the air.

Heat Exchanger

A heat exchanger moves heat from one fluid to another without letting them coming into contact with each other.

Heat Pump

A heat pump is an HVAC unit that heats or cools your space by moving heat.

HEPA Filter

HEPA stands for High Efficiency Particulate Absorbing. It’s a filter that removes particles from the air by trapping them as the air flows through it.


HSPF stands for Heating Seasonal Performance Factor, which is the heating mode of a heat pump that determines its efficiency over an entire season. The higher the rating, the more efficiently the heat pump performs.


A humidifier is a mechanism that adds moisture to dry indoor air, usually in the wintertime or in locations with a hot, dry climate.


A humidistat is an automatic device used to maintain humidity at either a fixed or adjustable setting.


HVAC stands for heating, ventilation and air conditioning.

Indoor Coil

The indoor coil is the interior part of the air conditioning system that is the counterpart to the outdoor unit. It’s attached to the furnace or air handler.


LEED stands for Leadership in Energy and Environmental Design and is a Green Building Rating System.

Load Calculation

A load calculation is an analysis of a home’s energy needs to determine which comfort system is best suited for its size.

MERV Rating

MERV stands for Minimum Efficiency Reporting Value. The MERV rating describes the size of the filter’s holes that let air to pass through. High efficiency and small filter holes result in a higher rating.

Modulating Heating

Modulating heating provides more fuel efficiency and better comfort control by continually adjusting to the fluctuating temperatures in a home.


NATE stands for North American Technician Excellence. NATE is a nationwide certification program for heating and cooling technicians.

Outdoor Coil

Located in the outdoor unit, the coil disperses heat from the refrigerant while turning the refrigerant from a vapor to a liquid.

Packaged System

A packaged system is an HVAC system where all the components are located in one cabinet.

R-22 Refrigerant

R-22 is the refrigerant that was previously used for residential air conditioners. It’s currently being phased out by the EPA.

R-410A Refrigerant

R-410A is a chlorine-free refrigerant that meets the EPA’s newest environmental guidelines.


A refrigerant is a substance that produces a cooling effect and is used in most air conditioning systems.

Scroll Compressor

A scroll compressor is a specially designed compressor that operates in a circular motion, instead of an up-and-down motion.


SEER stands for Seasonal Energy Efficiency Ratio. It’s an energy efficiency rating for air conditioners. The higher the SEER, the better the energy performance is.

Split System

A split system combines a heat pump or air conditioner with indoor components. They should be matched for optimal efficiency.


A thermidistat monitors the temperature and the humidity. It also regulates the heating or cooling system in order to maintain a set level.


A thermostat is a wall-mounted device that controls and regulates the heating and cooling equipment.


A ton is a unit of measurement used for determining cooling capacity. One ton equals 12,000 BTUH.


A ventilator is a system that swaps the stale indoor air with fresh, filtered outdoor air.


Zoning is a method of increasing comfort and energy efficiency by controlling when and where heating and cooling occurs, such as when using programmable thermostats and dampers. [1] [2] [3]

That’s a long list of words. It might seem overwhelming right now, but with enough repetition, you’ll have them committed to memory like any other pro.

Definitions are just the type of the iceberg, of course. Our HVAC programs will teach you not only what these words mean, but how they are applied. Enroll today.

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