The output or producing ability of cooling or heating systems. Cooling and heating capacities are referred to in British thermal units (BTUs) per hour.

A colorless, odorless, and highly toxic gas produced when carbon-containing fuels are burned. When a furnace becomes worn or is not properly maintained, CO can enter indoor space.

(Central Air) A system in which indoor air is cooled and dehumidified at a central location. The air is delivered to and from the rooms by an air handler and a system of ductwork. Contrast with “window air conditioner” and “ductless air conditioners”.

Abbreviation for chlorofluorocarbons, these are used as the refrigerant in air conditioning systems and heat pumps. They have been linked to the depletion of the ozone layer of the atmosphere.

An efficiency ratio that expresses the capacity of a system divided by electrical energy consumed or compares the amount of heat delivered to the amount of energy used. A higher the score means the equipment is more efficient. This ratio is used to rate heat pumps.

A general name for part of a heating or cooling system. A coil unit is made of tubing or pipe, and often has fins for cooling.

A pump in an air conditioning system that moves refrigerant from the evaporator coils indoors to the outdoor condenser and back again in a closed system. The compressor is like the heart of the system because it circulates the refrigerant throughout the loop. Compressors come in many designs and types.

A condensate drain is just a pipe that removes water from the air conditioner evaporator coils and/or 90% and above gas furnaces. Condensate drains has a P-Trap, Pipe, Drain Pan and if needed a Condensate Pump.

The outside unit of an air conditioning or heating system. This unit condenses the refrigerant from a gas to a liquid thus releasing unwanted hot or cold air from the building to the outside air. Sometimes called the "heat exchanger".

A network of tubes outdoors filled with refrigerant that remove heat from the heated gas refrigerant and convert the refrigerant into a liquid form again. The excess heat escapes into the outside air.

The fan in the outside unit that circulates air over the air-cooled condenser to change the refrigerant vapor into a liquid.

A measure of the ability of a unit to remove heat from an enclosed space. COP - Coefficient of Performance of a heat pump means the ratio of the rate of useful heat output delivered by the complete heat pump unit (exclusive of supplementary heating) to the corresponding rate of energy input, in consistent units and under operating conditions. Also see "capacity".

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

Abbreviation for Coefficient of Performance, capacity of a system divided by electrical energy it consumes. Sometimes used to describe heat pumps. Cross-reference HSPF.