"Kevin Cowans" wrote in message
...
Hello all

I hope someone can help me with this problem as it is starting to really
annoy us.

I leave the heating turned on at the timer in the airing cupboard and
control the heating with the thermostat situated in the hall.

After the heating has been on for a few hours (this is not constant) at
approximately 20 Degrees C there is a very loud banging that sounds as if
it is coming from the airing cupboard.

There is also a kind of crunching sound that comes from the radiators even
though they are warm.

If I run the hot water tap for a few seconds then the banging will stop.

It sound as though the water in the system is boiling and trying to vent.
Perhaps the boiler thermostat is not operating properly or the boiler
temperature is set too high. The noise could perhaps also be a zone valve
sticking or trying to open/close.
--
Dave Baker - Puma Race Engines