A thermostatic expansion valve is a key element to a refrigeration cycle; the cycle that makes air conditioning, or air cooling, possible. A basic refrigeration cycle consists of four major elements, a compressor, a condenser, a metering device and an evaporator.

As a refrigerant passes through a circuit containing these four elements, air conditioning occurs. The cycle starts when refrigerant enters the compressor in a low pressure, low temperature, gaseous form.

The refrigerant is compressed by the compressor to a high pressure and temperature gaseous state. The high pressure and temperature gas then enters the condenser. The condenser condenses the high pressure and temperature gas to a low temperature liquid by expelling heat either to the ambient air or a fluid similar to the action of an automotive radiator.

The low temperature liquid then enters the expansion valve where the valve acts on the refrigerant and changes it to a low pressure and temperature liquid. The low pressure and temperature liquid is now suitable for cooling.

The low temperature and pressure liquid enters an evaporator where, through the boiling refigerant, heat is absorbed from the air or another fluid and the cooling action takes place. After exiting the evaporator, the refrigerant is now a low temperature, low pressure gas.

The low pressure gas enters the compressor and the cycle repeats.

A requirement for 14 SEER or higher split system heat pumps
A requirement for many condensers or heat pump systems that use the new R-410A refrigerant
An optional upgrade for any other air conditioner or heat pump system