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?

Well, it could do. Without the radiators acting as a €œheat sink€�, the heat
exchanger is probably running hotter, especially if your HW system relies
on a simple thermo-siphon to circulate the water to your HW tank.

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...

Sooting isnt good. Suggests inadequate air supply but a certain amount in
an old open vented boiler is probably normal. A good clean out and
sweeping the chimney wouldnt go amiss!

Tim



--
Please don't feed the trolls