Thermal Expansion valves

A thermal expansion valve (often abbreviated as TEV, TXV, or TX valve) is a component in refrigeration and air conditioning systems that controls the amount of refrigerant flow into the evaporator thereby controlling the superheating at the outlet of the evaporator. Thermal expansion valves are often referred to generically as "metering devices" and are the most accurate way of metering the flow of refrigeration to the evaporator. Most high SEER equipment require the use of a TXV to achieve a specific rating, utility rebate, or tax credit.