Central Heating Air locks

[jvw45]

After 20 years we had a new boiler installed this summer although the pipework, pump and radiators were not changed. This is a very old large rambling house where the radiator system has been added to several times. Although the radiators have been vented initially, I have been away for three weeks and three adjacent radiators are now cold and all the radiators in the system are full. I have tried bypassing some of the radiators to no avail. Can anyone offer any advice?

Thanks

John Wood

 

[AnonymousImport]

There are a number of factors that could be the cause of this. Did the radiators ever get hot after the boiler was changed? Are these radiators more than 6m in height above the boiler? Was the pump change dwhen you had the new boiler installed?

If the pump is in the boiler let me know what type of boiler it is.

I am thinking that the pump isn't strong enough to reach thses rads.

The system could also need balancing.

I should be able to advise. Gasman

 

[oilman]

I am thinking that the pump isn't strong enough to reach thses rads.

Surely, this is not a problem if the system is full, since water going up is balanced by water going down. Or am I missing something?

 

[AnonymousImport]

I can see what you mean, but I have come cross a couple systems that have done this missing out the last rad people had in their new extensions. The problem was solved by changing a 15:50 to a 15:60.

I think it is the way the systems are piped especially if the new pipework is microbore.

Gasman

 

[ChrisR]

Try closing a lot of the other radiators - this would usually push put an air lock which could be stopping circulation.

If the rads have thermostatic valves then take the tops off to check that the central pins spring up and down and aren't stuck.

 

[Sam Gangee]

I had a house extension built, some years ago, and the radiators were added on to the old 13mm system (actually half inch I suspect) with microbore pipe. The downstairs one remained cold and the plumber said I'd have to have a whole new system fitted in the old part of the house.

But after 3 weeks the radiator suddenly became hot and has worked ever since.

 

[jvw45]

Thanks for the response.
To answer the questions. The pump was not replaced and has managed the job for the past six years when it was a replacement.

The rads are at the same height as the boiler.

The rads certainly did heat up after the boiler was changed. I have been away for sometime and my wife suddenly noticed that they had gone cold.

I have tried shutting off most of the other radiators, still to no avail. Grateful for any suggestions.

Thanks

John Wood

 

[oilman]

Did you have the system flushed, or were and cleaning chemicals added to the system? It's beginning to sound like a blockage somewhere.

 

[jvw45]

Yes the system was flushed and cleaned. You are probably right.

 

[ChrisR]

Hmm. It's looking like you may need to use a powerflusher on the system. Have known blockages shift with a new pump, or a pump put in backwards for a few minutes. Also by removing culprit rad and letting a good flow of water run out. (Garden hose will fit a 3/4" connecting union)