HVAC Glossary of Terms

AC – Air Conditioner
This appliance or system is designed to remove heat as well as dehumidify a room or building.

Normal atmospheric conditions of temperature and pressure.

A refrigerant mixture of two or more refrigerants.

Bubble point
The pressure at which a refrigerant liquid starts to vaporize.

Carbon monoxide
An odorless, colorless, tasteless, poisonous gas that’s produced when fuels like natural gas burn with insufficient air. A CO leak in your home can be extremely dangerous.

Component providing heat transfer to air when mounted inside an air handling unit or ductwork.

Coil cleaning
A technology that utilizes an appropriate amount of water pressure to remove the dust and debris from evaporator and condenser coils.

A modulating device for controlling airflow rates through ductwork.

Specialized pipes or channels that allow airflow within a home.

Energy star
Energy Star is a program by the U.S. EPA designed to help consumers and businesses save money by choosing energy-efficient products and technologies.

Evaporator coil
An evaporator coil is usually located indoors as part of a split unit. Inside the coil, refrigerant evaporates as it absorbs heat from the air that passes over it.

The HVAC filters used in your home’s heating and cooling system filter dust, pollen, pet dander, and debris out of the air.

A transfer of fluid volume per unit time.

Gauge pressure
The reading is taken from a gauge normally zeroed at atmospheric pressure so that pressures can also be read as a negative when below atmospheric pressure.

A facing across a duct opening, often rectangular in shape, containing multiple parallel slots through which air may be delivered or withdrawn from a ventilated space.

Heat transfer
Heat transfer describes the exchange of thermal energy between two interacting media passing through a heat exchanger, such as refrigerants, air, and water.

Heating, ventilation, and air conditioning is the technology of indoor and vehicular environmental comfort.

Intermediate fluid
A liquid or gas is used to transfer heat between two heat exchangers.

Indoor Coil
The part of an air conditioner or heat pump that absorbs the heat from the air in your house.

Mineral oil
A lubricant commonly used with HCFC and HFC refrigerants, with a low affinity for moisture.

Minimum outside air
The lowest amount of fresh air flow can be allowed into a recirculating system.

Natural refrigerant
Non-fluorochemical refrigerants, such as ammonia (R717).

NATE Certification
North American Technician Excellence (NATE) conducts rigorous, independent testing verifying the real-world knowledge and application of HVAC technicians and installers.Outside unit
The air conditioner’s outside portion is often referred to as the “condenser unit.” The outside unit’s job is to release the heat to the air outside.

Outside air temperature
A measure of the air temperature outside a building.

Packaged Units
Heating and cooling systems are contained in one outdoor unit.

Plenum space
An enclosed space inside a building or other structure is used for airflow.

A chemical that produces a cooling effect while expanding or vaporizing.

Refrigerant charge
The amount of refrigerant in kg in a closed system.

Scroll Compressor
A specially designed compressor that works in a circular motion.

Split System
A split air conditioning system consists of two main parts: the outdoor (condensing) unit and the indoor unit.

A thermostat is a device that monitors the indoor temperature and automatically adjusts your heating or cooling system to maintain the desired level.

Thermal zone
An individual space or group of neighboring indoor spaces that the HVAC designer expects will have similar thermal loads.

Upflow unit
A type of air conditioning system that discharges air into the conditioned space via a top-mounted discharge plenum.

Underfloor air distribution
A method for providing ventilation and space conditioning by using the air plenum below a raised floor.

Vacuum test
A test to check the gas tightness of a refrigeration system before charging it with refrigerant.

A ventilator is a device that replaces the stale, recirculated air with fresh, filtered outdoor air.

Water-Cooled System
A type of refrigerant-based air conditioning system that uses water as a condensing medium.

A watt is a derived unit of power in the International System of Units (SI).

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