In article , Andrew Gabriel
writes
I had an interesting problem with my Keston Celcius 25 condensing boiler
today. Switched boiler on to warm up a cold house. Arrive home a couple
of hours later to find radiators only luke warm and a wonderful gurgling
noise coming from the boiler. Actually, it was really quite loud if you
went outside to the flue terminal. Someone reported similar symptoms
here some months back and I speculated the combustion chamber was half
full of water.

Glad you fixed it...

I have had to remove the flexible flue pipe on mine to fix a leak of
condensate at the bottom and it is not too bad to refit. You need to
refit the bottom first (with the top not fastened) and use some silicone
sealant round the bottom of it. When I had the leak problem, Keston
denied that there should be any sealant on it (and what was I doing
messing with it anyway, that was a job for the installer). However they
had put some on mine, it just hadn't been applied properly, hence the
leak.

Having fitted the bottom you can stretch the pipe back up to the top
terminal and fit that.

Wee beasties can crawl down the flue pipe and end up in the burner /
condensate outlet. The flue pipe on mine is straight through the wall,
probably only about 12" long, so I can imagine things getting into the
burner and dying.
--
Tim Mitchell