Thermostatic radiator valves, or TRVs, are the name of the valves on the side of your radiator that are numbered 1 to 5. These valves allow you to set the temperature that you would like the individual room to be, but the way they work is often misunderstood. So, we thought we’d take a bit of time to explain how they work and how best to use them to ensure you stay warm this winter.
TRVs work by sensing the air temperature adjacent to the radiator and turning the flow of hot water to the radiator on or off depending on if the air temperature is above or below the set point. Interestingly, they do not work like a tap, they either turn the radiator on or off, there is not much proportional control. What the 1 to 5 settings relate to is the air temperature at which the radiator will be turned off.
So at setting 5 the radiator will turn off when the air temperature at the TRV is roughly 25°C, and at setting 1 it will turn the radiator off at roughly 15°C. The TRV essentially does not control how hot the radiator gets, just how long it stays at the maximum temperature set by the boiler. If you want the room to heat up faster, it is best to increase the central heating water temperature at your boiler. If you want the room to get warmer in general, it is best to turn up your TRV in that room. (The problem with increasing the central heating water temperature at your boiler is that you will need to adjust the rest of the house accordingly.)
The images below show this nicely, when the colour of the valve is blue the water runs into the radiator and when the value warms up the pin is pushed in and the flow stops.
The best way to ensure the efficient operation of your central heating system is to make sure that your TRV’s are working as they should be. Make sure that the TRV’s are clear of obstructions such as curtains etc so that air can flow to them freely. The next thing to do is set the central heating water temperature. The theory states that the most efficient way to run a modern boiler is to have the central heating water temperature as hot as it can be, as this is when the boiler is most efficient. I find that this makes my radiators scaldingly hot and with a young child in the house I prefer to set the temperature at my boiler to around 60°C to avoid skin burns from touching the radiators.
Once the central heating water temperature is set, the general advice is to set all of your TRV’s to ‘3’ except your bedrooms that should be set to ‘2’. Leave your house to warm through for an hour or so and check the temperatures in each room. You can adjust the TRV’s in each individual room up or down from there. If you find the house is not warm enough in general, you may need to turn the central heating water temperature up a bit. It is quite likely that you will want your living room warmer than the rest of the house so the TRV setting is likely to be a ‘4’ or even a ‘5’ and if you want to feel even warmer, you could always try a Radfan.