Thermostatic Radiator Valve

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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.

TRVs consist of two parts, a valve that opens or closes to control the hot water flow, and an actuator that controls the opening of the valve. The actuator adjusts the valve opening based on the temperature in the room via a mechanical linkage or pin connected to the valve. The actuator is usually a plastic unit containing a wax plug, the wax plug expands or contracts as the temperature of the room rises or falls. The plastic unit is preset by a screw mechanism that positions the wax plug a set distance from the connecting pin.

[edit] 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 one with 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.