Common HVAC Terms

ACCA – Air Conditioning Contractors of America.

Air Conditioning – The process of controlling the temperature, humidity, cleanliness and distribution of the air.

Air Handler – The portion of the central air conditioning or heat pump system that moves heated or cooled air throughout a home’s ductwork. In some systems a furnace handles this function.

Annualized Fuel Utilization Efficiency (AFUE) – A measure of furnace heating efficiency. The higher the AFUE, the more efficient the furnace. The government’s established minimum AFUE rating for non-weatherized gas furnaces is 80%.

Balance Point – The lowest outdoor temperature below which a heat pump is no longer sufficient to supply the heating needs of the home. This temperature is normally between 30° F and 45° F. Once the temperature outside dips below the balance point, auxiliary heat (usually electric heat strips in the air handler) is called on to aid the heat pump in providing heat to the home.

British Thermal Unit (BTU) – A measurement of heat energy. One Btu is the amount of heat required to raise one pound of water by one degree Fahrenheit. The higher the Btu rating, the greater the heating capacity of the system.

Carbon Monoxide (CO) – When carbon burns in a home without enough amount of air, a poisonous and odorless gas called as carbon monoxide is released.

Central Air Conditioner – A System in which air is treated at a central location and carried to and from the rooms by one or more fans and a system of ducts.

Coil – Equipment that performs heat transfer to air when mounted inside an air handling unit or ductwork. It is heated or cooled by electrical means or by circulating liquid or steam within it.

Compressor – The pump that moves the refrigerant from the indoor evaporator coil to the outdoor condensing unit and back to the evaporator. The compressor functions as the heart of the system, because it circulates the refrigerant in a loop.

Condenser – A component in the basic refrigeration cycle that ejects or removes heat from the system. The condenser is the hot side of an air conditioner or heat pump. Condensers are heat exchangers and can transfer heat to air or to an intermediate fluid.

Condenser Coil – A network of refrigerant-filled tubes where heat leaves the hot refrigerant vapor. The vapor then condenses into a liquid capable of absorbing more heat.

Condensing Unit – The portion of a refrigeration system where the compression and condensation of refrigerant is accomplished. Sometimes referred to as the ‘high side’.

Cooling Load – Heat which flows into a space from outdoors and/or indoors.

Cubic Feet Per Minute (CFM) – Abbreviation for cubic feet per minute, a standard measurement of airflow. A typical system requires 400 cfm per ton of air conditioning.

Dehumidifier – A device separate from an air conditioner that removes excess moisture from the air.

Department Of Energy (DOE) – A federal agency that sets industry efficiency standards and monitors the use of various energy sources.

Ductwork – A series of ducts that make up an entire household system that carry air throughout a building.

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

Energy Star® – A designation given by the Environmental Protection Agency to high-efficiency air conditioners that perform above and beyond the government’s minimum standards.

Environmental Protection Agency (EPA) – The U.S. Environmental Protection Agency (EPA) is a federal agency that develops and enforces federal environmental regulations and oversees the nationwide ENERGY STAR® program.

Evaporator – Absorbs heat from the surrounding air or liquid and moves it outside the refrigerated area by means of a refrigerant. It is also known as a cooling coil, blower coil, chilling unit or indoor coil.

Furnace – A component of an HVAC system that adds heat to air or an intermediate fluid by burning fuel (natural gas, oil, propane, butane, or other flammable substances) in a heat exchanger.

Gas Furnace Heat Exchanger – Located in the furnace, the heat exchanger transfers heat to the surrounding air, which is then pumped throughout your home.

Geothermal Heat Pump – A type of central cooling and heating unit that takes heat from the ground and uses it to heat home. This can be a very effective way to heat your home but can need the most amount of money to retrofit.

HEPA – a type of efficient air filter, acronym for High-Efficiency Particulate Air.

HSPF – Acronym for Heating Seasonal Performance Factor. The heating efficiency rating for heat pumps. The higher the rating, the more efficient the heat pump. There is no government established minimum HSPF rating for heat pumps.

HVAC – Heating, Ventilating and Air Conditioning. Used to refer to the industry at large, particularly dealers of heating and air conditioning equipment.

Heat Exchanger – A part of the system that transfers heat from the hot parts of the machine or a system to the cold parts of the machine or system.

Heat Gain — The amount of cooled air required to maintain a desired indoor temperature, despite heat collected by the structure through external and internal sources.

Heat Load Calculation – The amount of refrigerant and air flow it is going to take to heat or cool a space or place. Many factors go into heat load calculations.

Heat Loss – The rate of heat transfer from a heated space to the outdoors.

Heat Transfer – The movement of heat from one place to another, between two substances, or within a substance.

Heat Pump – Provides heating and cooling comfort as a split system or as a packaged system. A heat pump can be combined with a gas furnace for better performance when temperatures fall below freezing.

Humidity – Refers to the amount of water vapor in the air. High humidity inside of homes <60% could cause bacterial growth.

IAQ – Acronym for Indoor Air Quality.

Indoor Coil – Refrigerant containing portion of a fan coil unit similar to a car radiator, typically made of several rows of copper tubing with aluminum fins.

Load Calculation – A mathematical design tool used to determine the heat gain and heat loss in a building so that properly sized air conditioning and heating equipment may be installed.

North American Technical Excellence (NATE) – A nationally recognized certification that substantiates a technician’s knowledge and experience with heating and cooling systems.

Outdoor Coil/Condensing Unit – The portion of a heat pump or central air conditioning system that is located outside the home and functions as a heat transfer point for collecting heat from and dispelling heat to the outside air.

Refrigerant – Often referred to as FREON, PURON or gas.

Register – The type of cover you see in supply vents. It has operable louvers that allow you to control the air flow

Return – The side of the duct system that pulls air from the house back to the air handler to be conditioned again.

Seasonal Energy Efficiency Ratio (SEER) – A measure of an air conditioner’s cooling efficiency. The higher the SEER, the more efficient the product. The government’s established minimum SEER rating for air conditioners manufactured after January 2006 is 13.

Split System – A heat pump or central air conditioning system with components located both inside and outside the home. The most common design for home use.

Thermostat – A control device located inside your home or office used to set, maintain and control temperature levels. A thermostat will automatically turn on an HVAC system to maintain a preset temperature level and should not be used as a switch. Thermostats must be matched to the type of system used and wired accordingly.

Ton – A unit of measurement for air conditioner units equivalent to 12,000 BTUs per hour.

Two-stage Heating / Two-stage Cooling – Two-stage heating and cooling is considered to be more efficient, because it operates at low speed most of the time. However, on days when more heating or air conditioning is required, it switches to the next stage for maximum comfort.

Variable-Speed Motor – The fan motor used to drive a two-stage cooling system.

Zoned HVAC – An HVAC zoning system (also referred to as “zoned HVAC”) is a heating and cooling system that uses dampers in the ductwork to regulate and redirect air to specific areas of the home. This allows for the creation of customized temperature zones throughout the home for increased comfort and efficiency.