Given the current weather, anyone any ideas what causes problems with
condensing boilers when it isn't the condensate pipe? CAn flue pipes
themselves freeze?

I have a 3-month old Worcester Greenstar CDi COnventional, 30 IIRC. It
is mounted in the cellar, with the tope just below external ground
level. The Flue apparently does a dog-leg within the thick stone walls,
then exits about 12" above ground level, then has an extension kit to
raise the (often dramatic) pluming above window level. The condensate
pipe runs internally under the flooring, and empties into the drainage
sump. I've double checked, this pipe is clear and free-flowing.

Everything has apparently been fine til today, we had hot water and
radiators the morning. May or may not be relevant that this is the first
day for a fortnight where daytime temperatures here have struggled to
marginally above freezing. At lunchtime, I noticed that the light on the
boiler was flashing, and the display gave an error code "EA", which
appears to be about as specific as the average Microsoft error code. I
pressed the reset button, and it appeared to fire up, but only for 20
seconds or so, then I noticed water dripping from under the boiler.
Closer inspection revealed quite a lot of water behind the panelling,
suggesting it had been leaking for several hours at least, or
intermittently for longer. Switched it all off and took out the fuse.

Inside, there is water lying on a ledge above the level of the sump/
condensate apparatus, but no obvious source.

Outside, the flue did not appear to be frozen - there were some water
drops on the lower pipe, and it all sounded perfectly hollow. To be
sure, I poured a large jug of fairly hot water over it, back inside,
more water then appeared inside the boiler apparently from somewhere
around the flue exit, so presumably either from what I had poured on or
possibly from something melting internally.

I'm reluctant to turn it back on with the free water, currently have a
fan heater on it before I risk any electrical connection again.

We have had reported temperatures as low as -10C in this area in the
last couple of nights, so it is perfectly possible for unusual things to
have frozen, but I would have expected it not to have worked first thing.

Any ideas, do flue pipes freeze?

For the comfort and convenience of the locals, I have posted this
separately to The Shed, rather than simply cross-posting!

Cheers folks.

--
JonG
.... the hydrostatic paradox of controversy. Don't you know what that
means? Well, I will tell you. You know that, if you had a bent tube,
one arm of which was of the size of a pipe-stem, and the other big
enough to hold the ocean, water would stand at the same height in
one as in the other. Controversy equalizes fools and wise men in
the same way. And the fools know it. Oliver Wendell Holmes