HVAC Glossary of Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A-Coil
Two diagonal coils that are connected together to resemble the letter "A".

AC
Abbreviation for alternating current, an electric current that periodically reverses direction.

AC or DC
Usually seen as an abbreviation for units capable of operating on alternating or direct current.

ACCA
Air Conditioning Contractors of America.

Acoustical
Of or pertaining to sound. Usually seen when referring to the sound of a unit.

AFUE
Annualized Fuel Utilization Efficiency is a measure of your furnace's heating efficiency. The higher the AFUE percentage, the more efficient the furnace. The minimum percentage established by the DOE for furnaces is 78%.

AGA
American Gas Association, Inc.

Air Cleaner
A piece of equipment that removes unwanted particles from the air.

Air Conditioner
A system for controlling the humidity, ventilation, and temperature in a home or building.

Air-Conditioning and Refrigeration Institute (ARI)
ARI is an industry trade association that develops standards for measuring and certifying product performance.

Air Handler
The indoor part of an air conditioner or heat pump that moves cooled or heated air throughout the ductwork of your home. An air handler is usually a furnace or a blower coil.

ASHRAE
American Society of Heating, Refrigeration and Air Conditioning Engineer.

Bioaerosols
Microscopic living organisms suspended in the air that grow and multiply in warm, humid places.

BTU
British thermal unit. The standard of measurement used to guage the amount of heat required to raise the temperature of one pound of water by one degree (Fahrenheit).

BTUh
British thermal units per hour. 12,000 BTUh equals one ton of cooling.

Burner
A component that uses fuel to support combustion.

Burner Orifice
Air/gas mixing chamber opening of the burner.

CAE
The Combined Annual Efficiency is a measure of the amount of heat produced for every dollar of fuel consumed for the home.

Capacity
The ability of a heating or cooling system to cool or heat a given an area. For heating, this is expressed in BTU's. For cooling, it is given in tons.

Celsius
The metric temperature scale in which water freezes at zero degrees and boils at 100 degrees, designated by the symbol "C". To convert to Fahrenheit, multiply a Celsius temperature by 9, divide by 5 and add 32.

Central Air Conditioning System
System in which air is filtered at a central location and distributed to and from rooms by a fan system with an attached duct system.

CFM
The abbreviation for cubic feet per minute, commonly used to measure the rate of air flow in an air conditioning system.

Charge
Adding refrigerant to a system.

Compressor
The part of the outdoor air conditioner or heat pump that compresses and pumps refrigerant to meet household cooling requirements.

Condenser Coil
The outdoor portion of an air conditioner or heat pump that either releases or collects heat, depending on the time of the year.

Condensate
Vapor that liquefies due to a lowering of temperature.

Contactor
A switch that can make or break an electrical current as it cycles.

Crankcase Heater
This is the electric resistance heater on a compressor crankcase to keep the oil at a temperature higher than the coldest part of the system to prevent migration. Heat pumps require crankcase heaters; however, most new air conditioning units do not require a crankcase heater.

CSA
Canadian Standards Association.

Damper
This is a moveable plate found in ductwork that can be opened or closed to control airflow. They are also used in zoning to regulate airflow to certain rooms.

dB
A decibel is a unit used to measure the relative intensity of sound.

DC
Direct current electricity. This type of electricity flows in one direction only, without reversing.

Defrost
The process of removing ice or frost buildup from the outdoor coil during the heating season.

Degreeday
A computation that measures the amount of cooling or heating needed for a building. A degreeday is equal to 65 degrees Fahrenheit minus the average outdoor temperature.

Dehumidifier
A device used to remove moisture from the air. This unit reduces water vapor in the air by cooling the air below the dew point.

Diffuser
A grille over a supply duct having fins to distribute air in a defined pattern or direction.

DOE
The Department of Energy is a federal agency responsible for setting industry efficiency standards and monitoring the consumption of energy sources.

Downflow Furnace
A furnace that pulls in return air from the top and distibutes warm air at the bottom.

Drain Pan
This is also known as a condensate pan. This is a pan used to catch and collect condensate from the indoor coil.

Dry Bulb Temperature
Heat intensity, measured by a dry bulb thermometer.

Dry Bulb Thermometer
A device used for measuring air temperature independently of humidity.

Ductwork
A conduit through which air is supplied to an area. Ducts are typically made of metal, fiberboard or a flexible material.

DX
Direct expansion. A system in which the direct expansion of refrigerant passes heat along.

EER
Energy Efficiency Ratio. The ratio of the cooling capacity in British Thermal Units per hour, to the total electrical input in watts under ARI-specified test conditions.

Electronic Air Cleaner
An electronic device that filters out large particles in the indoor air.

ENERGY STAR®
Label given by the Environmental Protection Agency (EPA) to identify energy efficient products. ENERGY STAR products are more energy efficient and help reduce greenhouse gas.

EPA
Environmental Protection Agency.

Evaporator Coil (Indoor Coil)
The indoor half of an air conditioning system. These refrigerant filled tubes take heat and moisture out of indoor air as liquid refrigerant evaporates.

Evolution Control
Thermostat used with the Bryant Evolution System. This stat gives a homeowner maximum control over temperature, air flow, and humidity. This control also is able to run diagnostic tests on the system.

Evolution System
Bryant’s highest tier line of furnaces, air conditioners, and heat pumps. This group of systems gives the homeowner the most efficiency and money savings.

Expansion Valve
A refrigerant-monitoring valve with a temperature or pressure controlled orifice.

Fahrenheit
The temperature scale on which water freezes at 32 degrees and boils at 212 degrees; designated by the letter F. To convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit number, multiply by 5 and divide by 9.

Fan
Any piece of equipment that produces air flow.

Filter
Any device used to remove dust and other particles from the air to create healthier indoor air quality and prevent strain on an HVAC system.

Flue
Any conduit carrying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors.

Furnace
Part of an HVAC system that converts fuel to heat and supplies it to a home or building.

Fuse
A fuse is a protection device that prevents excess current from damaging a circuit.

GAMA
Gas Appliance Manufacturers Association.

Garage Heaters
Garage heaters are an excellent product for combating cold garages and workshops during the winter months. A newer example of these units is the Mitsubishi mini-split system.

Gas Furnace Heat Exchanger
The heat exchanger gives off heat to the surrounding air which is then distributed into the home.

Heat Gain
The amount of heat supplied to a space from all heat producing sources. These sources include appliances, solar energy, occupant respiration and lighting.

Heat Loss
Rate of heat transfer from inside a home or building to the outdoors.

Heat Pump
An automated compression cycle refrigeration system that can either heat or cool a space.

Heat Transfer
The movement of heat energy from one area to another.

Heating Coil
Any coil that serves as a heat source.

Hertz
A measure of the number of cycles or wavelengths of electrical energy per second.

HSPF
Heating Seasonal Performance Factor. This rating is used in measuring the heating efficiency of a heat pump. The higher the number, the more efficient the heat pump system.

Humidifier
A piece of equipmen that adds water vapor to the air to increase humidity.

Humidistat
A humidity sensing device designed to regulate humidity in a home or building.

Humidity
The measure of the moisture content in the air.

Humidity, Absolute
Ratio water vapor mass to the volume occupied by a mixture of water vapor and dry air.

Humidity, Relative
The percentage of moisture actually in the air compared to if it were fully saturated at that temperature.

HVAC
Heating, Ventilating and Air Conditioning.

Ignition
The lighting of a gaseous mixture to a particular temperature so that combustion can take place.

Indoor Air Quality
How clean or dirty the indoor air of a home is. IAQ can be improved with a number of devices including a humidifier, dehumidifier, electronic air cleaner, etc.

Indoor Coil (Evaporator Coil)
The indoor half of an air conditioning system. These refrigerant filled tubes take heat and moisture out of indoor air as liquid refrigerant evaporates.

Kilowatt (kW)
1,000 watts. A unit of electrical consumption measured by the total energy created by one kilowatt per hour.

Laminar Flow
Smooth undisturbed flow of a fluid.

Latent Heat
Heat given off or absorbed during phase change.

Legacy Series
Bryant’s basic tier of equipment. A homeowner can look to see the less energy savings and money savings with this tier.

Liquid Refrigerant
The compressor coolant used in the refrigerant cycle of a chiller for heat transfer.

Liquid Piping
Refrigerant piping from the condenser outlet to the evaporator inlet.

Load Swing
A large or radical change in cooling load requirements.

Matched System
A heating and cooling system comprised of products that have been certified to perform at promised comfort and efficiency levels when used together.

Media
The material in a filter that traps and holds dirt and dust.

MERV Rating
The MERV (Minimum Efficiency Reporting Value) rating of a filter describes the size of the holes in the filter that allow air to pass through. The higher the MERV rating, the higher the efficiency.

Micron
A unit of measure equal to one millionth of a meter, or one thousandth of a millimeter.

NADCA
National Air Duct Cleaners Association.

NEC
National Energy Council.

NEMA
National Electrical Manufacturing Association.

OEM
Original equipment manufacturer.

Operating Cost
The day-to-day cost of running your home comfort equipment, based on energy use.

Odors
Air contaminants in the form of gases.

Outdoor Coil
The outdoor portion of an air conditioner or heat pump that either releases or collects heat, depending on the time of the year.

Package Unit
A heating and cooling system contained in one outdoor unit. A package unit is typically installed outdoor at ground level or on the roof.

Preferred Series
Bryant’s mid-tier line of equipment. This equipment can provide a consumer with cost savings and energy savings.

Programmable Thermostat
A electronic thermostat with a built-in memory that can be programmed for different temperature settings at different times of the day.

PSI
Pounds per square inch.

PSIA
Pounds per square inch, absolute.

PSIG
Pounds per square inch, gauge.

PVC
Polyvinyl chloride; a type of plastic. Used primarily in venting high efficiency units along with draining.

R-410A Refrigerant
A chlorine-free refrigerant that meets the EPA's newest, most stringent environmental guidelines. Also referred to as Puron.

Refrigerant Lines
Two copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil.

Reciprocating Compressor
A compressor that uses pistons driven by a crankshaft to deliver high pressure gases.

Refrigerant
A chemical substance that while expanding and vaporizing produces a refrigerating effect.

Refrigerant Charge
The amount of refrigerant a system requires.

Scroll Compressor
A compressor that works in a circular motion, as opposed to up-and-down piston action.

SEER
Seasonal Energy Efficiency Ratio. A measure of seasonal or annual efficiency of a central air conditioner or air conditioning heat pump.

Self Contained System
A refrigerating system with self contained refrigerant lines. This is also know as a package unit.

Sensible Heat
Heat that when added causes a change in temperature.

Sensor
Device used to control conditions by detecting changes.

Setpoint
The indoor setting for temperature which is the desired comfort level for a homeowner.

Split System
The combination of an outdoor unit and indoor unit. The indoor unit usually consists of a gas or electric furnace and the outdoor unit usually consists of a heat pump or air conditioner.

Single Package
A heating and cooling system contained in one outdoor unit.

Termidistat
Used to monitor humidity in a home.

Thermostat
Device used to control an HVAC system.

Thermal Expansion Valve
A thermal expansion valve ( TXV) is a device used to monitor the flow of refrigerant entering the evaporator at a rate that matches the amount of refrigerant being boiled off in the evaporator.

Ton
A unit of measure used to determine the cooling capacity of a system. One ton of cooling is based on the heat needed to melt one ton (2000 lbs.) of ice in a 24 hour period.

Total Home Comfort System
The ultimate solution to providing you with consistent, customized home comfort, despite the ever-changing weather.

Two-stage cooling
The air conditioner/heat pump has a compressor with two degrees of operation. While the lower stage is adequate to meet cooling demands 80% of the time, a two-stage unit runs longer and produces more balanced temperatures.

Two-stage heating
The furnace has two stages of heat output. While the lower stage is adequate to meet heating demands 80% of the time, a two-stage unit runs longer and produces more balanced temperatures.

U-Factor
The factor used to determine the resistance of heat flow through various building materials.

UL
Underwriters Laboratories.

Upflow Unit
A furnace in which air is brought in through the bottom or side and distributes warm air out the top.

Vacuum
A pressure below atmospheric pressure.

Variable Speed Motor
A motor that automatically adjusts the flow of warm or cool air for ultimate comfort.

Volt
A measure of electrical force given to the electrons in an electric circuit.

Voltage
The force that pushes electrical current through wires and cables.

Watt
The unit of electrical power equal to the flow of one amp at a potential difference of one volt.

Wet Bulb Thermometer
Thermometer whose bulb is covered with a piece of water-soaked cloth. It is a type of temperature measurement that reflects the physical properties of a system with a mixture of a gas and a vapor.

Zoning
A method of partitioning a home into independently controlled zones for enhanced comfort and efficiency.