Trv Faulty ??

[fbg40]

I have two radiators in my lounge, one either side of the french doors. Both have Drayton TRV4 valves fitted. One of the radiators is not getting as hot as the other, maybe a few degrees "cooler". Could it be that the TRV on this rad is not working properly ? I have tried tapping it and turning it backwards and forwards a few times but with no success.If it is faulty, I believe it's possible to change the "top" without too much hassle - am I correct. Any advice would be greatly appreciated.
FBG40

[bhg481]

It's more likely that the radiators aren't balanced properly. Radiators are balanced by adjusting the "other" valve ie, the one at the opposite end of the radiator to the TRV. All the radiators in your house should reach the same temperature so adjust the radiator which is different from the rest of the house. The adjustment is made by pulling off the plastic cap on the valve and then turning the valve with a small spanner; try half a turn and see how it goes.

[fbg40]

Thanks BHG, will have a look.
FBG40

[SlackAlice]

The sensing head is widely available
https://www.screwfix.com/p/drayton-trv4-sensing-head/7109r

Do 'bhg481' suggestions first though ☺☺☺

[bhg481]

Just to expand on balancing; the longer the pipe-run to a radiator the greater the resistance in the flow to that radiator. The radiator with the longest pipe-run should have the fixed valve fully open; as the radiators get closer to the pump the lockshield valve should be partly closed to try to get the same resistance for all radiators. This is usually a one-off adjustment, hence the cap on the valve to dissuade you from adjusting it unnecessarily.

[bobbinwales]

Hi. We have some problem in are batheooms but with a heated towel rails heated with central heating water. One is now stone cold. Have tried bleeding and turning the two knobs at the bottom. Anyone any suggestions please?

[fbg40]

BHG and Slack Alice
Thanks for the replies. Have tried adjusting the lockshield valve but it's fully open.Would it be worth swapping heads ? I have other rads with the same TRV, so thought I might swap one that does not matter so much and see how it goes rather than spending out on a new one ? Thanks again
FBG40

[SlackAlice]

//Would it be worth swapping heads ? I have other rads with the same TRV, so thought I might swap one that does not matter so much and see how it goes rather than spending out on a new one ? //

Worth a try, easily swapped over.

[malagabob]

The ones either side of the French doors,try setting the hottest one to 3-4 the coldest to 6.

[fbg40]

An update on my question - sorry it's been so long !
Have tried all of the suggestions, swapped heads over yesterday as the last try - nothing has changed. One rad still get nice and hot, the other, although fairly, warm remains cool ( not cold) in the bottom right hand corner. (Facing the rad). Could it be sludge in the rad ? Not desperate, just annoying. Thanks again for all the responses.
FBG40

[donny48]

Whilst changing the tops did you check that the pin under the head is working properly. when the top is removed the valve should open fully and heat the rad. The pin can stick.

[bhg481]

Sludge is a real possibility although, because I always have Fernox 1B in my system, I have no personal experience of it.

[fbg40]

Thanks again for such prompt responses. As always, will take all on board.
FBG40