An air conditioning refrigerant that contains chlorine. According to the terms of the Montreal Protocol, the U.S. EPA agreed to a phaseout schedule for HCFCs, including R-22. R-22 will cease to be available by the year 2020.

The refrigerant that is replacing R-22. It contains no chlorine and is not associated with ozone depletion.

A rating of insulating or thermal resistance value. The ability to slow heat flow rather than to transmit it. A higher "R", number means better insulating value.

A compressor whose piston or pistons move back and forth in the cylinders.

Returning used refrigerant to the manufacturer for disposal or reuse.

Removing, cleaning and reusing refrigerant.

A chemical that produces a refrigerating effect while expanding and vaporizing. Most residential air conditioning systems contain R-22 or R-410A refrigerant. New HVAC systems will use the R-410A refrigerant as R-22 is scheduled to stop production by the year 2020.

The amount of refrigerant required to be in an air conditioning or refrigeration system. Used as a verb, the process of adding or "charging the refrigerant". Keeping the correct amount and type of refrigerant is critical for peak operating performance.

Also referred to as (Line-set). Set of two copper lines connecting the outdoor unit and the indoor unit.

Also referred to as (Floor Grille) or (Ceiling Grille). Combination grille and damper assembly covering an air opening or end of an air duct.

The ratio of the amount of vapor contained in the air to the greatest amount the air could hold at that temperature. Normally expressed as a percentage.

Also referred to as (Return). The path of air as it goes to the air-handler or furnace so it can be cooled or heated. The Return side should be "balanced" with the supply side to achieve optimum airflow and comfort. Sometimes described as "return", or "return air". Contrast with "supply side".

A device in a heat pump that reverses the flow of refrigerant as the system is switched from cooling to heating.