A Thermostatic Radiator Valve, (TRV), is a self regulating valve fitted to hot water heating system radiators. The TRV controls the temperature of a room by regulating the flow of hot water to the radiator.
As the temperature of the room increases the medium whihch could be wax, liquid or gas expands, pushing the pin down and restricting the flow of hot water. As the room cools the plug contracts, the pin is let out a little and more heat is admitted into the room. This process, completely self contained and without complex electronic circuitry, keeps the room temperature at a desired constant level. TRV's filled with gas medium react faster and hence save more energy needed for space heating, compared with slower reacting TRV's filled with wax or liquid.
