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hvac terminology

Common HVAC Terminology Every Homeowner Should Know

Common HVAC Terminology Every Homeowner Should Know

You've hired a professional to work on your air conditioner unit. The technician tells you they're going to charge the system, so it runs more efficiently. What on earth does that mean? Your technician likely uses many other HVAC terminologies when explaining what they've done to your system. If you're feeling confused, you aren't alone. Continue reading to learn common HVAC terminology all homeowners should know.

Why Bother Learning HVAC Terminology?

You may be wondering why you should bothering learning common HVAC terminology. It isn't your chosen career path, so why invest the time it takes to learn the industry jargon?

If you own a home, you'll need to hire an HVAC technician at some point. These professionals work with heating, ventilation, and air conditioning. In terms of heating, this generally refers to natural gas heat, oil heating, and electrical heating.

Understanding the most basic, commonly used terminology can help you know what your HVAC tech is saying. A good professional will try to relay the issue or give details on the project in layman's terms. There are certain situations, however, where there just isn't a proper substitution for the correct words.

Industry Terms

There are many scientific and industry-specific terms you'll hear used by HVAC professionals. These terms generally refer to how air conditioning or heating work. The most common HVAC terminology is listed below.


The acronym AC stands for alternating current. This is a type of current where the polarity is continually reversing.


The acronym "AFUE" stands for "American Fuel Utilization Efficiency." This is a measurement used to determine how efficient a furnace is by using a math equation. The equation compares the amount of heating input versus output.

Air Conditioner

An air conditioner is a device used to change the humidity levels, temperature, or quality of air inside a building. Many units are designed to do some or all of these essential tasks at one time. Smaller, cheaper units may only alter the temperature.

Airflow Volume

The airflow volume is the amount of air that is circulated inside a specific space. The volume is measured in cubic feet per minute, or cfm.

Air Handler

The air handler is the indoor part of the air conditioning system. It includes the circulation fan, as well as the evaporator/condenser coil. The coil's two parts are useful in either summer (the evaporator) or winter (the condenser).


BTU is an acronym for British Thermal Units. This is a measurement of the heat required to raise or lower the temperature of one pound of water one degree. The water degrees are measured in Fahrenheit.


BTU/h is a measurement used in the HVAC industry. It represents the amount of British Thermal Units per hour.


A burner is a device that facilitates the combustion of air and gas. The gas (or alternative fuel) is allowed into this device through the burner orifice.


HVAC capacity is the total output produced by a heating or cooling unit. This output is measured in BTU/h.

"Charging a System"

When an HVAC technician is "charging a system," it means they're adding coolant or refrigerant to it. These fluids are necessary for a system to run efficiently.


The compressor is a type of pump that increases the pressure of refrigerant gas.

Condensate Pan

This is also sometimes known as the drain pan. Its job is to collect the liquefied refrigerant vapor. Once received, the pan helps funnel the liquid into the drain line so it can be disposed of.

Condenser Coil

A condenser coil is usually the outdoor coil or the one housed in your outside unit. Its job is to remove excess heat from refrigerant during the summer months. Removing this heat is vital because refrigerant won't work correctly if it's too warm.

Condenser Fan

This is a fan that speeds up the movement of air over the condenser coil. In this way, the condenser fan helps the coil to remove heat from the refrigerant.


DC is an acronym for direct current. Unlike AC, which shifts directions at regular intervals, DC moves in only one direction.


A damper is a device found at junction points of ductwork. It's comprised of plates of sheet metal that can be opened or closed to help control the airflow in a specific zone.


A degree-day is a number calculated by taking away the average outdoor temperature of a local area from 65 degrees Fahrenheit. This calculation is used to help determine how much cooling or heating will be needed to keep a building comfortable.


A dehumidifier is a device that takes the humidity out of the air.

Downflow Furnace

This is a type of furnace with an intake on the top. This leads down to an air discharge at the bottom of the furnace.

Duct Work

This refers to a network designed to deliver air from the HVAC unit to different zones inside a building.

Indoor Coil

This is also referred to as an evaporator coil. It's designed to absorb heat in the air so it can change liquid refrigerant into vapor. This initiates the cooling process.

Expansion Valve

This is the valve that meters refrigerant levels. It does this through temperature or pressure control.


The flue is the vent that removes byproducts created through the combustion process from a furnace.


This is the primary heating component for homes. The furnace helps combustion happen and then circulates the heat created throughout the house. A fan assists circulation.

Heating Coil

The heating coil acts as a source of heat for the heating system.

Heat Pump

A heat pump assists in both heating and cooling. It does this by transferring heat between two reservoirs.


HSPF is an acronym for Heating Seasonal Performance Factor. This is a term used to define how efficient a residential heat pump system is.


A humidifier does the exact opposite task of a dehumidifier. Instead of taking away humidity, it adds moisture to the air.


This device measures humidity. It also works to turn the humidifier on and off as needed.

Package Unit

A package unit refers to a heating and cooling system that is contained in a single outdoor unit.

Radiant Floor

This is a type of radiant heating system. The system works by circulating fluids through tubes located beneath the flooring.

Reciprocating Compressor

This is a type of compressor used to compress refrigerant with a piston action. A reciprocating compressor is found in cooling systems.


Refrigerant is a working fluid used to transfer heat into or out of interior space. This fluid is used in air conditioners, heat pumps, and refrigerators.

Industry Associations and Organizations to Know

Besides the HVAC terminology listed above, there are some industry-specific associations and organizations that homeowners should know about. When vetting a potential contractor, you're likely to come across some of these names.


ACCA is the Air Conditioning Contractors of America. They're a non-profit association that represents a large population of individuals who work in the indoor environment and energy services industry.


AGA is the American Gas Association, Inc. This is an association that represents more than 200 companies that deliver natural gas.


AHRI is the Air-Conditioning, Heating, and Refrigeration Institute. This is a trade association that represents the manufacturers of HVACR and water heating.


ASHRAE is the American Society of Heating, Refrigeration, and Air-Conditioning Engineers. They're a global society that places a heavy emphasis on bettering society and human life. They do this by focusing on energy efficiency, indoor air quality, and sustainability within the HVAC industry.

Energy Star

Energy Star is a program created by the United States Environmental Protection Agency. It's not a mandatory program but is instead voluntary. The Energy Star program is designed to help people save money and protect the climate through the highest energy efficiency.


NATE stands for North American Technician Excellence. It is the nation's largest non-profit certification organization for people working in the HVAC industry.

What If You Still Don't Understand?

If you still don't understand what your HVAC technician is saying after learning these standard terms, simply tell them as much. An excellent tech will take the time to ensure you understand. Most technicians won't assume you know HVAC terminology, so don't be afraid to speak up.

Do You Have More Questions About Common HVAC Terminology?

There are a lot of scientific and industry-specific terms used by HVAC professionals. The most common of those are listed above.

Do you have more questions about common HVAC terminology? Or do you require the assistance of an HVAC technician for your home's heating and air conditioning systems?

Contact us today. We will be happy to answer any questions you still have. We can set you up an appointment, too, if desired.


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