Heating & Cooling Industry Terminology & Definitions

Guide to Heating & Cooling Terms & Definitions

Advanced Reciprocating Compressor

Type of compressor that uses a more efficient process for compressing refrigerant for better cooling efficiency.

Air Handler

The portion of your air conditioner or heating system that forces air through your home's ductwork.


British Thermal Unit. Used for both heating and cooling, BTU is a measure of the heat given off when fuel is combusted. Or for cooling, it's a measure of heat extracted from your home. (One BTU is approximately equal to the heat given off by a wooden kitchen match.)


Stands for Cubic Feet per Minute. A measurement of airflow that indicates how many cubic feet of air pass by a stationary point in one minute.
The higher the number, the more air is being forced through the system.


The ability of a heating or cooling system to heat or cool a given amount of space. For heating, this is usually expressed in BTUs.
For cooling, it is usually given in tons.

Carbon Monoxide

A colorless, odorless, highly poisonous gas produced when carbon-based fuels, such as natural gas, burns without sufficient air nearby.


Part of a split-system heat pump or air conditioner's outdoor unit that controls the pressure applied to the refrigerant, necessary for taking in heat to warm your home with a heat pump or getting rid of heat to keep your home cool.

Condenser Coil

Part of the outdoor portion of a split-system air conditioner or heat pump. By converting refrigerant that is in a gas form back to a liquid, the coil sends heat carried by the refrigerant to the outside.


A type of "valve" used in duct work that opens or closes to control airflow. Used in zoning to control the amount of warm or cool air entering certain areas of your home.


A type of furnace that takes cool air from the top and blows warm air to the bottom-commonly used where furnaces must be located in a second-floor closet or utility area.


Hollow pipes used to transfer air from the Air Handler to the air vents throughout your home. Ductwork is one of the most important components
of a home heating and cooling system.


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.


ENERGY STAR® is a government-backed program helping businesses and individuals protect the environment through superior energy efficiency. Products with the ENERGY STAR rating will be efficient and save cost on energy bills.

Electronic Air Cleaner (EAC)

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.

Energy Saver Switch

An energy-saver switch causes the air conditioner's fan and compressor to cycle on and off together, reducing energy use.

Evaporator Coil

Part of a split-system air conditioner or heat pump located indoors. The evaporator coil cools and dehumidifies the air by converting liquid refrigerant into a gas (or vice-versa). A blower moter, typically in a furnace, then moves air over the coil to either heat or cool your home.

Fan Coil

An indoor component of an air conditioner or heat pump system, used in place of a furnace and evaporator coil, to provide change the refrigerant from a gas to a liquid (or vice-versa) and blow air over the coil to cool or heat your home.


Term used for Heating, Ventilation, and Air Conditioning.

Heat Exchanger

The part of a furnace that transfers heat to nearby air.

Heat Pump

A product that works just like an air conditioner in cooling mode; however, in heating mode, the refrigerant flow is reversed and heat is extrated from the outside air too heat your home.

Horizontal Flow

A type of furnace, installed on its "side", that draws in air from one side, heats it and sends the warm air out the other side. Most often used for installations in attics or crawl spaces.


A piece of equipment that adds water vapor to heated air as it moves out of the furnace. This adds necessary moisture to protect your furnishings and reduce static electricity.


A variable speed compressor that slows down or speeds up to match the heating and cooling load of the space. This also ensures higher comfort.

Load Estimate

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.

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, and used according to design and engineering specifications.

Operating Cost

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

Payback Analysis

Overall measure of the efficiency and value of your home comfort system. By combining your purchase price and ongoing operating costs, a payback analysis determines the number of years required before monthly energy savings offset the purchase price.

Puron Refrigerant

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 from Freon 22*.

R-22 refrigerant

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.

Reciprocating Compressor

A type of compressor used in air conditioners that compresses refrigerant by using a type of "piston" action.


Removing, cleaning and reusing refrigerant.

Refrigerant Lines

Two copper lines that connect the Condenser (Outdoor) Coil to the Evaporator (Indoor) Coil.


The Seasonal Energy Efficiency Ratio is a measure of the cooling efficiency of your air conditioner or heat pump. The higher the SEER number, the more efficient the system is at converting electricity into cooling power.

Setback Thermostat

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

Single Package Product

One outdoor unit that contains both a heating and a cooling system.


Smart Recovery starts the system in advance to be sure that each zone reaches your selected temperature setting at the scheduled time.

Split System

Refers to an air conditioner or heat pump that has components in two locations. Usually, one part of the system is located inside (evaporator coil) and the other is located outside your home (condenser coil).


The Thermidistat™ Control monitors temperatures both inside and outside, as well as indoor humidity and adjusts system operation to maintain the temperature and humidity levels set by the homeowner.


Unit that monitors and controls your HVAC system products.

Thermostatic Expansion Valve

A thermostatic expansion valve (TXV) is precision device used to meter the flow of liquid refrigerant entering the evaporator at a rate that matches the amount of refrigerant being boiled off in the evaporator.


A unit of measure for cooling capacity. One ton = 12,000 BTUs per hour.

Total Home Comfort System

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

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.


UL is an objective, non-profit organization that tests and rates electrical products for public safety.


A type of furnace that draws cool air from the bottom and blows the warmed air out the top into the duct work. This type of furnace is usually installed in a basement or an out-of-the-way closet.


A ventilator captures heating or cooling energy from stale indoor air and transfers it to fresh incoming air.


WeatherShield is a special coating of the outdoor condensing unit coil to resist corrosion from salt air found mainly in coastal areas.


A way to increase your home comfort and energy efficiency by controlling when and where heating and cooling occurs in a home. Programmable thermostats are used to control operating times of the equipment. Dampers are used to direct air flow to certain parts or "zones" of the home.