Thermostatic Radiator Valve
2008-08-18

If you're throwing off the covers in the bedroom, just to keep the lounge warm then you should get Thermostatic Radiator Valves fitted.

A Thermostatic Radiator Valve, (TRV), is a self regulating valve fitted to hot water heating system radiators. It is a device that controls the flow of hot water to the radiator in effect controlling the temperature of the area of effect of a radiator. So as the room warms to a preset temperature, the valve will gradually close reducing the amount of heat given out. Conversely, as the room cools, the valve opens to allow more hot water in to the radiator so that it can give out more heat. 

Fitting thermostatic radiator valves will allow you to control the temperature accurately in each room where they are fitted. This can save considerable amounts of energy and cost by preventing some rooms in your home from becoming overheated. The valves are relatively cheap, starting at under £10 each, and are simple for a plumber to fit, so the cost is quickly recouped. The valves will soon pay for themselves in savings made on heating costs. Controlling the temperature separately in each room will also allow you to set bedrooms to be slightly cooler than living areas, leading to a better night's sleep.

Thermostatic Radiator Valves 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. 

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.

Thermostatic radiator valves can’t turn off the boiler when the whole house is warm, so to get the best out of the valves they should be used in conjunction with other heating controls, namely a programmer and a room thermostat.

Programmers allow the central heating and hot water to be switched on and off at different times throughout the day to suit the home’s needs, while a room thermostat senses the air temperature of the home and simply turns the heating on and off in order to keep the temperature at a set level. Both these jobs can be done by one device called a programmable room thermostat, which sets when the heating comes on and what temperature it reaches when it is on. It means different temperatures can be set for various times of the day and days of the week, saving energy and money.

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 thermostatic radiator valves should not be used in the same room as one with an electronic thermostat. The operation of the two devices is not compatible and would interfere with each other so that effective temperature control would be lost.