2 cold rads. TRVs seem fine and bled them. Please help!

youngplug · 27 Nov 2010

Hi,

Last year we fitted a new central heating system and through last winter it all worked fine.

But now 2 of the downstairs radiators are cold. As far as we can reach them in the wall and the floor upstairs, the pipes running down to them are cold too. We've checked the TRVs and the pins spring back no problem. We've bled them, no air. We've tried turing all other radiators in the house off and turning the combi up to max. I wouldn't have thought that the radiators are full of muck because it was all brand new last year.

But it doesn't seem to making any difference.

Does anyone have any adivce?

Thanks

bster · 27 Nov 2010

if its a combi and hot water is fine then the pump is ok, if all other rads are turned off and they still wont heat then it is probably a blockage in a pipe that is common to the two rads, is the pipe work to the rads 8,10 or 15 mm. and are the other rads downstairs all working?
and are the valves on the problem rads definatly open (both ends)?

Hugh Jaleak · 27 Nov 2010

Whats the system pressure sitting at?

youngplug · 27 Nov 2010

Hi!

The pipework is all 15mm to the radiators, fed off the 28mm loop. And yes there's just one 15mm pipe that's common to both these rads.

The rads everywhere else work fine. And we've checked and rechecked the valves both in and out of the problem rads and we're sure they're all open.

We thought it might be an airlock that's developed over the summer and we hadn't noticed because we don't put the heating on much and this is the first time we've used these rads this year. Could that be it? But how would we get rid of it?

Thanks!

youngplug · 27 Nov 2010

The system was at 1.2. We put a bit more in to see if it would help it round and it's now at 1.8. The boiler is an Ariston E-combi condensing 38kW.

bster · 27 Nov 2010

not sure you will no answer to this but.. is it a 2 or 1 pipe system?

youngplug · 27 Nov 2010

Errr... not sure what you mean about 1 or 2 pipe system. But I can describe it to you.

We have a 28 mm pipe for the main flow and another separate one for the return to the boiler. All of the rads (except these two problem rads) have their own smaller 15mm pipe from the main flow and connecting back to the return. These 2 rads share a 15mm supply, but they are tee'd, not in series.

Does that answer the question?

Hugh Jaleak · 27 Nov 2010

Pressure is ok at that. Usual trick would be to turn all other rads off, and one of the affected two, then try and force any blockage/air lock through, but if you've already tried that then it may not work.... Next stage is to remove rad, and draw some water off from the valves into a bucket, check there is no obstructions or air locks in the pipework.

youngplug · 27 Nov 2010

Yes I don't fancy keeping the other rads off much more as the boiler has started giving error lights and getting too hot I think.

You suggested taking the rad off and opening valve at the end of the pipe. If we have to, then will do that. But one of these rads has a run off valve on it. Would it work to open this and let the water run through there? (Would save me emptying/removing the rad)?

Hugh Jaleak · 27 Nov 2010

You could try that, turn off opposite end first. Might clear any problems in that leg of the pipework. Make sure pressure is kept topped up though, partly to drive out any air lock, partly as if you let it drop too low you'll create more hassle than you solve.....

youngplug · 27 Nov 2010

Right. We'll give it a try tomorrow then. Happy Sundays! Will let you know how we get on.

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2 cold rads. TRVs seem fine and bled them. Please help!

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