I have one radiator that has gone completely cold. Rest of system is functioning normally, bled it an no airlocks, valve pin in TRV moves freely. What is my problem likely to be and how do I diagnose it? I can only think of a frozen pipe (seems unlikely in a house that has constantly been heated and in a room with two rads) or a stuck valve at a level below the pin.
Chris R
I've had it where the lockshield valve on a rad was open such a tiny amount and some debris got stuck in it and blocked the flow. I opened the valve a bit more and it cleared the blockage and the rad was piping hot within a couple of mins.
I have cured this by turning off all the other rads and fully opening the lock valve on the offending radiator.
Mike
Has the system been cleaned, drained, and upon refilling had an inhibitor added? If not it could be a sludge build-up.
If so go to your local plumbers merchant (not a DIY shed - WAY toooooooo expensive) and get a cleaner and an inhibitor. Part drain the system, pour the cleaner into the header tank and refill. Run the system for a couple of days (during which this radiator should start working) and then drain it down completely - the water will likely be black. Refill, run it for a few hours, and then drain again whence the water should come out clean. Pour the inhibitor into the header tank and refill.
Best thing I ever did and I've never had any sludge problems since.
Has the system been cleaned, drained, and upon refilling had an inhibitor added? If not it could be a sludge build-up.
If so go to your local plumbers merchant (not a DIY shed - WAY toooooooo expensive) and get a cleaner and an inhibitor. Part drain the system, pour the cleaner into the header tank and refill. Run the system for a couple of days (during which this radiator should start working) and then drain it down completely - the water will likely be black. Refill, run it for a few hours, and then drain again whence the water should come out clean. Pour the inhibitor into the header tank and refill.
Best thing I ever did and I've never had any sludge problems since.
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The system hasn't been drained for years, but has always had inhibitor in it. We did have some minor plumbing done, though, about two weeks ago, without draining the system - replacing a leaking valve.
Chris R
It could be an air lock that has worked it's way round to that radiator or pipework to that radiator. Switch of all the other radiators to se if you can get that one warm.
It could be an air lock that has worked it's way round to that radiator or pipework to that radiator. Switch of all the other radiators to se if you can get that one warm.
-------------------------------------------------------- Thanks, tried that but no joy. Also turned the lockshield valve on an off and opened the drain c*ck on the valve - runs with clear, cold water, not under much pressure.
Chris R
Are you sure your TRV valve is open? Hold the pin with a pair of pliers and give a gentle pull. Also give a firm tap to the side if that fails.
If this does not work you have an air lock. Close each valve in turn and bleed radiator for a time to see if that moves it.
Do you have a condensing boiler? I understand that they need a certain pressure to work correctly - mine is
1.5 bar. If the pressure is not correct you will get problems. If you do have a condensing boiler I think you have to top up the pressure after bleeding the rads.Mr Pounder
Do you have a condensing boiler? I understand that they need a certain pressure to work correctly - mine is
1.5 bar. If the pressure is not correct you will get problems. If you do have a condensing boiler I think you have to top up the pressure after bleeding the rads.----------------------------------------------------
The TRV pin moves up and down freely. I don't have a condensing boiler.
Chris R
Was the rad was okay before you had the recent plumbing job done?
Mr Pounder
Was the rad was okay before you had the recent plumbing job done?
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Yes, so my guess is that the plumbing work introduced some air into the system.
Chris R
Or something. I don't think it is air but it could be. Give that rad one hell of a bleeding into a bucket and I mean one hell of a bleeding. Half fill the bucket. If it is an older double rad it may have *two* bleed nipples. My rads are old; the one in the bathroom is double and has *two* bleed nipples. Do you have two pipes going into one valve?? This is important. I used to be in central heating but this was 40 years ago.
Mr Pounder
That would be combi boilers not condensing boilers that require 1 bar to work.
Mine is a condensing boiler and requires 1.5 bar to work. I know, I bought it and I set the pressure after I found a very small leak.
Or something. I don't think it is air but it could be. Give that rad one hell of a bleeding into a bucket and I mean one hell of a bleeding. Half fill the bucket. If it is an older double rad it may have *two* bleed nipples. My rads are old; the one in the bathroom is double and has *two* bleed nipples. Do you have two pipes going into one valve?? This is important. I used to be in central heating but this was 40 years ago.
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Bled it, bashed it, bled all the other rads in the house, turned off all other rads in the house, nothing doing. With the lockshield valve shut opened the drain c*ck, but it soon runs dry. Runs again when bleed valve is opened, so there is just no water flowing in from the supply side. time for a plumber I fear.
Chris R
I had a similar situation and in the end decided to change the valves on both sides of the radiator. This solved the problem. I assumed that although the plunger did move up and down it was not functioning correctly.
km
It might be an idea to ring the bloke who did your plumbing job and blame him.
Mr Pounder
What boiler is that ?
I *think* it is a Baxi Megoflo 34, but I could be wrong. The boiler is in the loft. I've been up there once today and nearly broke my stupid neck; I'm not going back up there.
Mr Pounder
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