In article , Roger Mills
wrote:
On 13/06/2021 16:18, jkn wrote:


FWIW one reason for doing this *now* is that the back boiler has
starting making 'kettling' noises when it starts up. We've fairly
recently set the controller to not put the radiators on, but I wouldn't
have thought that that would have caused any such issues? It is looking
to me that the heat exchanger is really sooted up - I actually fitted a
new thermocouple, and cleaned the jet out, a month or so ago, and it
seemed fine then. I'd quite like to fix/understand that even if we do
finally sort out a new boiler...

J^n


What colour is the boiler flame? If the HE is sooting up it suggests
that there's not enough oxygen, so the flame will be yellow instead of
blue. Make sure that the air supply to the burner isn't blocked and - if
possible - check the gas pressure at the burner when it's firing.

If the boiler is kettling, that's likely to be due to scale on the
*inside" of the HE rather than soot on the outside. As JR says, there
are additives which will help with that.

screwfix is a good source - "noise reducer"

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle