How to fit a Thermostatic Radiator Valve (TRV)

What is a Thermostatic Radiator valve?

A Thermostatic Radiator Valve (TRV’s) is a self-regulating valve fitted to your hot water heating system radiator that will individually control the temperature in the room by changing the flow of hot water to the radiator.

 How does a TRV work?

TVR’s are actually pretty simple in how they operate.  They detect the temperature in a room with a highly responsive metal spring filled with either liquid or wax. When the room gets hot, the liquid in the spring expands and pushes on the valve jumper. This slowly closes the valve when the desired temperature has been reached.

Where can I fit TRV’s?

TRV’s can be fitted throughout the home. The most important thing to note when fitting TRV’s is to not fit a TRV on the radiator in the same room as your room thermostat. As the radiator valve closes and cools the air, the room thermostat will never reach its set temperature and knock the heating system off.

Can TRV’s reduce my heating bills?

Yes, when installed as part of a complete set of heating controls that include timers and a room thermostats, TRV’s can provide householders with substantial savings in the major area of energy expenditure, 84% of the energy use in a domestic house is in heating and hot water (Ref. Department of Energy and Climate Change).

Tests carried out in 2013 at The Energy House at Salford University by The BEAMA heating controls association, TACMA, found that savings of 40% can be achieved in a standard terraced house. They also calculated that, at 2013 energy prices, this could save a householder £409.46 per year (if they fitted a full set of controls where none were previously present.)

Disclaimer: The information contained in this page is for information purposes only. We cannot be held responsible for any problems that arise as a result of following the guidance contained on this page. We strongly recommend that plumbing work of this nature only be attempted by a qualified and fully insured expert plumber. 

How to fit a TRV

TRV -0028Ok we’ll start. For this purpose we will assume that you’ll already know how to drain down a heating system, if you don’t check out our guide here first.

Once drained the next step is to let air into the system where you want to install TRV’s. Open the valve with your radiator key and you will hear the air rushing into the radiator.

Now once the hose you used to drain the system has stopped running water that means you’re ready to start the valve change.

1. Removing the old lock shield valve.
TRV -0033Using grips and an adjustable spanner, slacken off the nut that is coming out of the radiator pipework. Once loose, and if your pipes coming out of the floor have enough flex, you can gently move the pipework out to see if all the water has drained out of the system. Remember to have something handy to catch any last bits of water and transfer it to a bucket.

TRV -0030Next, loosen off the 15mm pressure fitting on the bottom of the valve so that you can then remove the whole valve from the radiator pipework.

TRV -00352. Fitting the new thermostatic radiator valve.

Sometimes the new TRV’s will not fit on the radiator insert. All new TRVs are supplied with a new insert so usually the one on the radiator will need removing with a simple hex tool the is inserted into the hole and then loosened with an adjustable spanner.

TRV -0037Take some PTFE wrap around the thread of the new insert and push the insert into the radiator and tighten it up. The old nut and olive should be ok to use but if prefer then just pull the nut off and use a pair of grips to pull the olive off, just be careful not to damage the pipe.

TRV -0039Push the fitting back on and tighten up everything. Remove the top plastic cap which will reveal the valve. Quickly test that the springs moves up and down by pushing the valve. Put the TRV head unit on the top and have it set to 5.

TRV -0041

Problems with TRV’s

After a summer of being closed, TRV’s can get stuck causing your radiator to not feel hot but this doesn’t mean it necessarily needs replacing. All TRV’s have a small pin which is the valve jumper and its these that can become stuck. Two simple steps can solve this problem.

1/ Remove the TRV knob (they come apart either by unscrewing a holding ring or removing a plastic lug and twisting the collar.

2/ Once the head is off you should see a pin, move this pin in and out with a pair or pliers  or lightly tap it with a small hammer. Once the radiator has started to get hot, pop the TRV knob back on

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