Are you having a difficult time understanding all the different terms in the HVAC industry? We have compliled a list of common HVAC terms and definitions to help alleviate some of the stress researching an air conditioning system can create. If you cannot find the term you are looking for don’t hesitate to contact our knowledgeable staff of trained and experienced air conditioning technicians.
Annual Fuel Utilization Efficiency applies to furnaces – both gas and oil. It describes the percentage of heat produced for every dollar of fuel consumed.
The Air Conditioning, Heating, and Refrigeration Institute is the authority on HVAC ratings such as SEER, EER, HSPF, and AFUE
The process of installing dampers in ductwork to direct airflow throughout a building. The dampers allow the contractor to adjust the amount of air that enters a Room.
An IAQ control strategy to remove various airborne particulates and/or gases from the air. The three types of air cleaning most commonly used are particulate filtration, electrostatic precipitation, and gas absorption.
A device used to control temperature and humidity of the air.
In HVAC it is the control of the quality, quantity, and temperature-humidity of the air in an interior space.
Air Handler or Air Handling Unit (AHU)
Used instead of a furnace for electric heating applications. The equipment that includes a blower or fan, heating and/or cooling coils, and related equipment such as controls, condensate drain pans, and air filters. Does not include ductwork, registers or grilles.
A substance capable of causing an allergic reaction because of an individual’s sensitivity to that substance.
The air external to a building or device.
A fan mounted on an attic wall used to exhaust warm attic air to the outside.
HVAC term for a passive or mechanical device used to ventilate an attic space, primarily to reduce heat buildup and moisture condensation.
The device in an air conditioner that distributes the filtered air from the return duct over the coil/heat exchanger. This circulated air is cooled/heated and then sent through the supply duct, past dampers, and through supply diffusers to the living/working space.
British Thermal Unit (BTU)
The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit, equal to 252 calories.
Carbon Monoxide (CO)
A colorless, odorless but poisonous combustible gas with the formula CO. Carbon monoxide is produced in the incomplete combustion of carbon and carbon
compounds such as fossil fuels (i.e. coal, petroleum) and their products (e.g. liquefied petroleum gas, gasoline), and biomass.
Chlorofluorocarbons are ozone-depleting chemicals and are being phased out by the Environmental Protection Agency. HVAC refrigerant R-22 is an example of a CFC that is being phased out and replaced by an HCFC.
A device used to compress air for mechanical or electrical power production, and in air conditioners, heat pumps, and refrigerators to pressurize the refrigerant and enabling it to flow through the system.
The device in an air conditioner or heat pump through which the refrigerant is circulated and releases heat to the surroundings when a fan blows outside air over the coils. This will return the hot vapor that entered the coil into a hot liquid upon exiting the coil.
Condenser or Condensing Unit
The component of a central air conditioner that is designed to remove heat absorbed by the refrigerant and transfer it outside the conditioned space.
Air that has been heated, cooled, humidified, or dehumidified to maintain an interior space within the “comfort zone.” (Sometimes referred to as “tempered” air.)
The quantity of heat that a cooling appliance is capable of removing from a room in one hour.
Controls that vary airflow through an air outlet, inlet, or duct. A damper position may be immovable, manually adjustable or part of an automated control system. Different types of dampers are used in air balancing and zoning
A device that reduces the level of humidity in a room or home.
Diffusers and Grilles
Components of the ventilation system that distribute and return air to promote air circulation in the occupied space. As used in this document, supply air enters a space through a diffuser or vent and return air leaves a space through a grille.
The round or rectangular tube(s), generally constructed of sheet metal, fiberglass board, or a flexible plastic-and-wire composite, located within a wall, floor, and ceiling that distributes heated or cooled air in buildings.
Energy Efficiency Ratings (EER) measure the efficiency with which a product uses energy to function. It is calculated by dividing a product’s BTU output by its wattage.
Electronic Air Cleaner
An electronic device that filters out large particles and contaminants in indoor air. It then electronically pulls out tiny particles that have been magnetized, such as viruses and bacteria, drawing them to a collector plate.
Conditions other than indoor air contaminants that cause stress, comfort, and/or health problems (e.g., humidity extremes, drafts, lack of air circulation, noise, and over-crowding).
Occurs when air escapes an area, specifically a building, and is the opposite of infiltration.
A device that removes contaminants, by mechanical filtration, from the fresh air stream before the air enters the living space. Filters can be installed as part of a heating/cooling system through which air flows for the purpose of removing particulates before or after the air enters the mechanical components.
Blower motor that operates at one speed only.
Forced Air System or Furnace
HVAC term for a type of heating system in which heated air is blown by a fan through air channels or ducts to rooms.
A registered trademark for a cholorfluorocarbon (CFC) gas that is highly stable and that has been historically used as a refrigerant. Typically called R-22 in HVAC terms.
Combustion heating appliance in which heat is captured from the burning of a fuel for distribution, comprised mainly of a combustion chamber and heat exchanger, also houses blower motor and circuit board.
Hydrochlorofluorocarbons are the safer refrigerant alternative to chlorofluorocarbons, or CFCs, which deplete the ozone layer. R-410a is a HCFC.
The heat that flows from the building interior, through the building envelope to the outside environment.
A product that works just like an air conditioner in cooling mode; however, in heating mode, the refrigerant flow is reversed and heat is extracted from the outside air too heat your home.
The rate of heat flow required to maintain a specific indoor temperature; usually measured in Btu per hour.
High efficiency particulate resistance (filters).
A measure of the moisture content of air; may be expressed as absolute, mixing ratio, saturation deficit, relative, or specific.
An acronym for heating, ventilation, and air-conditioning
Indoor air pollutant: Particles and dust, fibers, mists, bio-aerosols, and gases or vapors.
HVAC acronym for Indoor Air Quality
A series of studies performed to determine the heating or cooling requirements of your home. An energy load analysis uses information such as the square footage of your home, window or door areas, insulation quality and local climate to determine the heating and cooling capacity needed by your furnace, heat pump or air conditioner. When referring to cooling this is often known as a Heat Gain Analysis, since a home’s cooling requirements are determined by the amount of heat absorbed through the roof, entry way and walls.
A heating and cooling system comprised of products that have been certified to perform at promised comfort and efficiency levels when used together, and used according to design and engineering specifications.
Chemicals that contain carbon. Volatile organic compounds vaporize at room temperature and pressure. They are found in many indoor sources, including many common household products and building materials.
A state of matter in which solid or liquid substances exist in the form of aggregated molecules or particles. Airborne particulate matter is typically in the size range of 0.01 to 100 micrometers.
Fine liquid or solid particles such as dust, smoke, mist, fumes, and fog found in air and emissions.
HVAC term for an air compartment connected to a duct or ducts.
Regular and systematic inspection, cleaning, and replacement of worn parts, materials, and systems. Preventive maintenance helps to prevent parts, material, and systems failure by ensuring that parts, materials and systems are in good working order.
A type of thermostat that allows the user to program into the devices’ memory a pre-set schedule of times (when certain temperatures occur) to turn on HVAC equipment.
Puron® refrigerant is an environmentally sound refrigerant designed not to harm the earth’s ozone layer. Federal law requires that all manufacturers phase out ozone depleting refrigerants in the next few years. Puron refrigerant is approved by the US Environmental Protection Agency as a replacement for R-22 a.k.a. Freon.
R-22 is a single component HCFC refrigerant with low ozone depletion potential. It has long been used in a variety of air-conditioning and refrigeration applications in a variety of markets. Per U.S. EPA regulations, new R-22 cannot be used in new systems effective in 2010, although service quantities of the refrigerant may be produced until 2020.
R-410a is a blend of hydrofluorocarbons also known as HFCs which does not contribute to the depletion of the ozone layer. This is the “new refrigerant” which replaces R-22 systems. R-410a is not compatible with R-22 equipment due to its higher psi operation.
A measure of the capacity of a material to resist heat transfer. The R-Value is the reciprocal of the conductivity of a material (U-Value). The larger the R-Value of a material, the greater its insulating properties.
In HVAC a thin, reflective foil sheet that exhibits low radiant energy transmission and under certain conditions can block radiant heat transfer; installed in attics to reduce heat flow through a roof assembly into the living space.
The compound (working fluid) used in air conditioners, heat pumps, and refrigerators to transfer heat into or out of an interior space. This fluid boils at a very low temperature enabling it to evaporate and absorb heat.
Air that is returned to a heating or cooling appliance from a heated or cooled space.
The central heating or cooling system contains a fan that gets its air supply through these ducts, which ideally should be installed in every room
Seasonal Energy Efficiency Ratio (SEER)
A measure of seasonal or annual efficiency of a central air conditioner or air conditioning heat pump. It takes into account the variations in temperature that can occur within a season and is the average number of Btu of cooling delivered for every watt-hour of electricity used by the heat pump over a cooling season.
Split System Air Conditioner
HVAC term for an air conditioning system that comes in two to five pieces: one piece contains the compressor, condenser, and a fan; the others have an evaporator and a fan. The condenser, installed outside the house, connects to several evaporators, one in each room to be cooled, mounted inside the house. Each evaporator is individually controlled, allowing different rooms or zones to be cooled to varying degrees.
Condition that exists when an equal amount of air is supplied to and exhausted from a space. At static pressure, equilibrium has been reached.
HVAC term for the duct(s) of a forced air heating/cooling system through which heated or cooled air is supplied to rooms by the action of the fan of the central heating or cooling unit.
A unit of air cooling capacity: one ton is 12,000 Btu per hour and 350-450 CFM. Most residential systems are available in 1.5 – 5 Tons.
Two Stage Compressor
Two Stage Compressors are capable of two levels of operation, a low stage and a high stage. Properly sized equipment will operate 80% of the time in low stage, enhancing efficiency and comfort with lower humidity levels and quieter operation. It’s like getting two air conditioners or heat pumps in one system.
Volatile organic compounds are found everywhere from cleaning supplies to paint. Look for ‘Low VOC’ or ‘No VOC’ labels
Variable Speed Blower
Blower motor that changes speeds based on the amount temperature differential from the thermostat setting and ambient temperature of the room. Variable Speed Blower have increased efficiency from Fixed Speed Motors along with greater dehumidification.
A component of a heating or ventilation appliance used to conduct fresh air into, or waste air or combustion gases out of, an appliance or interior space.
HVAC term for a device mounted in the vent connector that closes the vent when the heating unit is not firing. This traps heat inside the heating system and house rather than letting it draft up and out the vent system.
A tube in which combustion gases from a combustion appliance are vented out of the appliance to the outdoors.
Caulking, weather-stripping,sealing holes and cracks to reduce air infiltration and exfiltration into and out of a building.
A material used to seal gaps around windows and exterior doors.
An area within the interior space of a building, such as an individual room(s), to be cooled, heated, or ventilated. A zone has its own thermostat to control the flow of conditioned air into the space.
The combining of rooms in a structure according to similar heating and cooling patterns. Zoning requires using more than one thermostat to control heating, cooling, and ventilation equipment.