heating problem/thermo valves?

when 1st switching on my heating his year some rads did not get warm. I have thermo valves to most rads. When I switched off all rads except furthest one, thinking I had air lock, rads in lounge got hot. When I opened valves, rads cooled. All rads bled no air. I do not know what is wrong. Are valves at fault?

Probably the pins are stuck in on your TRV's. This is caused by leaving them on their usual setting during the summer rather than setting them to their max setting when the system is not in use.

If you close the Lockshield on a rad where you suspect this the rad will not bleed at all because there is no way for water to get into the rad.This confirms the TRV is closed if the valve is set to the max position

My official answer is that the valves need renewing but read on and you may get them to work again.

Unsticking the pins by taking the head off and pulling the pin out a little can be a scary task when you pull too far and water comes out of it, especially if you then lose the pin through the gap in the floor where the pipe comes through. Its the only way to do it sometimes and doesnt guarantee that the valve that the pin held in the closed position can be unstuck, so you often need to carefully tap the valve in the hope that it will free itself.
Every year I get a job to free off some stuck Danfoss RAVL valves at a local dentist. He reckons and rightly so that it is more cost effective for me to do this once a year than get new valves which could still get the same problem. On those valves I just take the pin out clean it off, add a little silicone grease and put it back in again. Fortunately all the stuck parts inside the valve have worked free with gentle tapping and working the pin in and out.

Beware as not all valves are that easy to work with

Thanks for the advice, it is what I expected but I am still somewhat confused. I obviously have a rad in the bathroom that does not have a trv and this is the same in the en suite. They tend to react the same. Should I replace the trv's on the other rads, draining the system completely. The trv's fitted are now about 10 yrs old??

adrianclark said:

Thanks for the advice, it is what I expected but I am still somewhat confused. I obviously have a rad in the bathroom that does not have a trv and this is the same in the en suite. They tend to react the same. Should I replace the trv's on the other rads, draining the system completely. The trv's fitted are now about 10 yrs old??

Click to expand...

Hold on a minute the tend to react the same bit .... Do you mean that they arent working as well? Ok that could be another problem.

Can you give us a bit more info about your system and boiler?

My crystal ball is a little cloudy but I think I can see a Potterton puma

Right, here goes. The boiler is a Worcester Delglo. It is situated in the airing cupboard and in effect, the burner is situated directly under the hot water tank. There is a header tank in the loft and is at its normal level. The pump, next to the boiler, is working.
As I mentioned, there was no problem till I turned the heating on for the first time. I sought advice from a couple of friends who know a bit about plumbing. One suggested the trv's were suck, the other suggested an airlock. I have removed the 'knob' of the trv's and pushed in the pin in an attempt to release any stuck pin. The only exception to this is the larger rad in the kitchen as I cannot get that one off. I then turned all inlets off with the exception of this lager rad which is the furthest one from the boiler. This resulted in the two rads in the living room getting hot!! The heating is on at the minute. Some rads are hot, others ae warm but the pipe on the inlet side of he valve is hot. The two rads without trv's, bathroom and ensuite are warm, I can keep my hand on it all the time.
The boiler has been in the house since it was built, about 25 yrs I think.
I will probably get it changed but had intended to wait till after Xmas.

Theres a few other things that could be wrong with the system / boiler

In no particular order.


sludge in system
Weak pump, or pump erroneusly turned to low speed
Airlock in pipework perhaps near the diverter valve if one is fitted Can you see a vent near the cylinder.
Divertor valve if fitted not opening properly.
Boiler stat is a more remote possibilty seeing as you say that rads are not as hot as they should be.

If a trv is stuck on a rad then that rad will usually not heat up at all.
A circulation problem as above is far more likely in the light of new information than trv fault




Im not at all familiar with a worcester delglo.