In article ,
Adrian writes:
The boiler (Worcester Greenstar 30CDi, LPG, non-combi) has started
sulking.

After a morning of luke-warm showers, I poked my nose into the understairs
cupboard it lives in, to find "EA" flashing on it. Reset, and it fired
right up. EA appears to be a bit of a general catch-all error code.

Next morning? Same again.
Next morning? Same again. Over the weekend, with looking at it more
often, I've had to reset it several times. It gets up to temp, we've got
a cylinder of nice hot water, and the heating's been fine between resets.

This morning, it won't fire up at all. EA. Reset. Gurgle. EA. Reset.
Gurgle.

From the flue vent outside, there's loudly audible gurgling.

We've been here 18mo, not had it serviced or looked at at all in that
time. The house was more-or-less empty for five years before, since the
extension it lives in was built, so it was clearly new at that time.

I don't know this boiler, but...

My guess would be the condensate drain is blocked, and the heat
exchanger is filling up with condensate, to the point where it's
now blocked the pathway for the combustion gasses. If so, the
girgling (assuming that's a good description of the noise) will
coincide with the fan running (and be very audiable from the flue
as you say). It will eventually prevent the burner ignition, and
cause the burner to go out shortly after ignition.

Had this with my Keston a couple of times. The blockage was in
the bottom of the heat exchanger and I cleared it by disconnecting
the drain hose from it (nothing ran out) and poking a piece of
wire up it (several pints then came gushing out, so watch that it
isn't going to gush all over the circuit board, or a nice new
carpet). The Keston does have a detector for blocked condensate in
the U-trap (which would catch the classic frozen pipe case), but
as the blockage was before this, it couldn't see it. Don't know if
yours will detect this, so assume the blockage could be anywhere
in the condensate drain path. The condensate does wash debris out
of the heat exchanger in normal operation, and this could build up
in some places in the pipework, such as a U-trap. Clearing that is
part of routine servicing.

For the Keston (where it tends to block inside the heat exchanger),
I now avoid this problem by pouring a couple of pints of water in
the flue outlet a couple of times a year, which will wash out the
bottom of the heat exchanger before the dirt builds up enough to
block it. This may not be a good idea in other boiler designs.

--
Andrew Gabriel
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