Condensing units are familiar temperature-control devices in refrigerators, air conditioners, heat pumps and chillers. They move energy in the form of heat by compressing a gas known as a "refrigerant," then pumping it through a system of coils and using the air around the coils to heat and cool spaces. Electronic controls, fans, pumps and coils manage the condenser's work.

Condensers apply pressure to gas until it becomes a liquid--forcing energy out as heat--and then circulate the cooled liquid through a closed system, where it absorbs heat as it returns to the compressor.

The first condensers converted the "ice box" to a "refrigerator," deriving the name from the gas used by the condenser that sat on top of the appliance.

Condensers contain a compressor, refrigerant, one or more pumps, fans and a system of tubing to manage the flow of the refrigerant.

All condensers are "heat exchangers;" fans force air over the metal coils to cool areas "outbound" from the condenser, or it is ventilated on the "return" (warm) side.

Condensers range in size from small units in office water fountains to huge machines used to air condition buildings as large as the Pentagon.

Condenser units facilitate living and working in areas that were once considered uninhabitable, heat pumps provide efficient heating for temperate locales and refrigeration extends the life of perishable food.