In article ,
says...

"Jayne" wrote in message
.com...
In article ,
says...
Jayne wrote in message
d.com...

We have 11 rads in total, 4 have TRV's (bedrooms). All radiators are
getting hot. It does actually sound as though the water is bubbling
(red hot). Any chance the thermotat could have gone in the boiler?

I had similar trouble with a boiler a few years ago which was caused
by sludge and scale build up. As I understand it this can clog up the
heat exchanger meaning that heat from the burners is not dissipated
quickly enough causing the boiler to overheat and clank. I solved the
problem with a couple of doses of a pretty caustic product from Fernox
(DS40 as I recall) and a lot of flushing. Search the archives on
Google, there are several threads on this.

However, my clanking started up pretty much as soon as the boiler came
on. I can't explain why yours should take 20 minutes to start.

I have just had the plumber round and he thought he sorted it. All the
time he was here nothing happened. Typical. He said it was air in the
system. He bleed the pump and lots of air came out. It didn't make a
noise and didn't cut out. Until now. It's started again, back to
square one :O(

Hmmm. Either you have a leak which is causing air to get into the system or
it could be that your stat is cream crackered as you said earlier. Does the
problem go away if you turn the boiler stat down? If there's air getting in
where is it coming from? Are there any tell tale leaks or patches of rust on
the radiators?

--
Malc

Can't see any leaks or patches at all. The plumber said the stat on the boiler
isn't supposed to work as the wall stat and the water stat control the
boiler. The problem seems to get a little quieter when you turn the
boiler down, but this doesn't ring true with what the plumber is saying.