TRV's which don't shut off!

[Deansplit]

I've restored my house and at the point of filling the CH system to test for leaks. But some TRV's just don't switch off! And some do, then without touching them, when the system's been emptied and refilled, they decide to leak, and I mean really soak the place! So this tells me that when the rads and heat are all on, turning the faulty ones off means they're not actually off, wasting money, right? Is this is a common problem? I don't really know how they work, They are made by Weatherall (I think) and 7 yrs old, but thought they had a longer lifespan than that! Also means I can't remove rads when installed if required!

Any help appreciated.

 

[Steve]

New ones have a "fully off" position, that older ones I believe didnt - they'd weep water through if I understand it. On new ones you can take off the TRV head and fit a decorating cap which forces the pin fully tight shut.

Though if your system has a lot of dirt in it, this may be blocking your TRVs from closing properly.

All A TRV is, is a normal "tap" with a thermostatic head that pushes down on a sprung pin in the tap to close the valve. The "tap" therefore without the head on, is fully open by default.

Perhaps use this opportunity to install new TRVs? And set them all appropriately, not using them as on/off switches.

 

[cantaloup63]

Have you used "decorators caps" to close the TRV's? Also, you can get blanking caps which screw on. where the radiator tails enter the valves.

 

[Deansplit]

Yeah, these have fully off too - plus frost setting, but on off, some leak real bad, i've attached a bit of pipe and an end cap on 3 or 4 of them to stop the leaking, but know that those ones will never fully switch off when in full operation!

 

[Deansplit]

no, haven't used decorators caps, I think I do have these, but that may cure the initial problem with testing the system without rads on, but it still surely means that when all rads are on, some will never shut off?

 

[cantaloup63]

A decorators cap closes the valve completely. The TRV head operates in a slightly different way since it require a full expansion of the liquid or spring within it to push the pin down fully.

 

[sooey]

no, haven't used decorators caps, I think I do have these, but that may cure the initial problem with testing the system without rads on, but it still surely means that when all rads are on, some will never shut off?

It easy to tell if a TRV is shutting the rad off.
Turn the TRV off and the heating on, if the rad stays cold the TRV is shut.

 

[Deansplit]

Turn the TRV off and the heating on, if the rad stays cold the TRV is shut.

Well that's a bit late by the time I have the house all back together and ready to move in! I would have thought if leaking slightly (which some are) it's not enough to make the rad warm though.

 

[misterdubya]

For future reference, you can try un-doing the TRV head and pop a 5 pence piece (or similar) in it and re-attach to the body. Then turn the valve off.

 

[cantaloup63]

For future reference, you can try un-doing the TRV head and pop a 5 pence piece (or similar) in it and re-attach to the body. Then turn the valve off.

Used to be a 1p or 2p coin. There's inflation for ya