"Jayne" wrote in message
.com...
Recently moved house and found we have a very noisy/clanking boiler.
When the boiler has been on for about 20 minutes it starts for a few
minutes then cuts out and starts up again. This is a typical example
when the boiler is on. Air in the system you may say, but I have bled
the radiators about 30 times with little or no air coming out now. We
have been here 2 months and drained the system twice because of a
previous problem and a radiator relocation.

Any ideas?

This is kettling I reckon. Do you have TRVs fitted to all your radiators? If
so leave one open and see what happens. Are the radiators getting hot?

Generally with TRVs if they are fitted to all radiators then the boiler
heats up, the TRVs close when the room is warm enough and the boiler can't
dissipate the heat inside so it boils. You should have one radiator open all
the time, ideally the one in the same room as your room stat if you have
one.

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MAlc