Thermal Expansion Valves, or TXV's for short, are crucial internal components to any HVAC system. The TXV valve regulates the superheat point of the refrigerant released into the evaporator portion of an HVAC system. Thermal Expansion Valves are an essential element in any heat pump, and rarely fail. But when they do, you can trust HeatDoneRight.com to get you the one you need in a hurry!