Operation

As the temperature of the room increases the wax 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 temperature control is suitable for large rooms or buildings that are not constantly occupied, （such as warehouses and garages）, where precise control of the room temperature is not critical. They are subject to fairly wide swings in temperature inside the heated space due to external conditions, e.g. ambient temperature and/or wind velocity and direction, and since their setting is not readily adjusted, once the initial setting is made it is rarely changed.

It should be noted that TRVs should not be used in the same room as an electronic thermostat. The operation of the two devices are not compatible and would interfere with each other so that effective temperature control would be lost.