"SS" wrote in message
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"Doctor Drivel" wrote in message
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"SS" wrote in message
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"YAPH" wrote in message
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On Sun, 10 Jan 2010 17:31:20 +0000, JonG wrote:

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.

There should be a flue gas sampling point on the flue connection just
above the boiler. (There are two caps: one for the air inlet and one
for
the flue: you're after the one that communicates with the inner part of
the concentric flue assembly). If you pour water down the flue (not
air) hole it should run away via the condensate syphon/sump and
pipework
to the drain. If it doesn't your condensate waste system is blocked
somewhere along the line.

If you've got water in the air intake you may have further
difficulties.

--
John Stumbles -- http://yaph.co.uk

I'd rather have a full bottle in front of me
Than a full-frontal lobotomy

I had the same problem of cutting off, it turned out the condensate pipe
was frozen as it enters the ground sump.
A couple of kettles of boiling water sorted it.

It is a recently installed combi system so I had phoned the installer
and he advised me as he has had numerous call-out for that very thing.

It is incorrecty fitted. It should not ice up.

Cant argue with you as I am not a plumber, but from a laymans point of
view if the condensate pipe comes from internal to external in very
cold/extreme conditions then unless it has a heater of some sort on it
then surely it is possible for it to freeze?

Based on what you are saying then there must be a standard that makes it
impossible for it to freeze and if there is would you please advise as I
will take this up with the installer as the boiler is only 6 months old.


As you say, any external pipe with the occasional flow of water can freeze.
It is normal practice for a longer run to be of a larger diameter, which
needs a lot more ice to plug the pipe up.

Most condensate traps fill up and empty using a siphon action. The idea is
that you get a few 100 mils of water every so often, rather than a drip, to
lessen the likelihood of freezing.