DIY Doctor

central heating

Postby claire.83 » Tue Sep 30, 2008 8:16 pm

We drained our system at the start of the summer to remove a radiator. we haven't put the radiator back yet, but we did put the central heating and hot water back on and both worked fine.

we then just had the hot water on through the summer, although we later switched it off when there was a screaching noise coming from the pump upstairs.

We've then since tried to start up both, but neither will work. when we swtitch them both on we get strange noises, but the boiler does boot up-but only for a short while-it goes off after about 20seconds.

we thought there may have been an airlock but the downstairs radiators have water up to the top, but the upstairs ones dont.

the bathroom one starts to heat in the first 20seconds or so, but then nothing happens when the boiler goes out.

we think it's the thermo in then boiler, but we're not sure, also there's the strange noise we can't explain.

cann anyone help?
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Simply Build It

Postby plumbbob » Tue Sep 30, 2008 10:48 pm

The logical explanation is an airlock around the pump. The fact that the boiler fires for only a few moments is caused by a lack of water being circulated around the system. Basically, the boiler is only heating a minimal amount of water rather than the whole system.

The screeching noise from the pump is caused by the bearings running dry (caused by the airlock) and if this is allowed to continue, will destroy the pump very quickly (if it already hasn't done so).
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Postby Steve the gas » Wed Oct 01, 2008 5:09 am

Sounds like a large air-lock
Do you have tanks in the loft?
If so check the little one has water in it?
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