Gurgling boiler

[Adrian]

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'm phoning around local fixers today, but anybody got any bets?

[Tim+]

What's the system pressure like? When did you last top it up?

Tim

[Tim+]

Oops, I was presupposing it was a sealed system. If not, worth checking that the header tank isn't empty.

Tim

[Adrian]

When it first threw an error, tail end of last week, it was about 0.5bar, so I topped it up to 1.0 - and it's stayed there.

[Adrian]

You presupposed right. I should have mentioned that. Pressurised hot water cylinder, with solar HW. Wet underfloor heating. Does the exact same whatever is on or off out of the heating (three zones/timers) or water.

Condensate drain appears to be all internal. There's plastic heads towards a wall and the back of the kitchen units, presumably joining the sink drain.

[Andrew Gabriel]

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.

[Adrian]

We have a winner!

Having a peer underneath, there's a flexible plastic tube going to a push- in connection, tie-wrapped to the frame. That push-in is the start of the hard plastic solvent-welded pipework going out towards gawd-knows-where.

Snip the tie-wrap, move it down as far as it will, and unplug the flexi. After a few drips, a steady flow started and emptied mebbe a litre and a half into a handy bucket. Blowing down the hard plastic was impossible at first, but a couple of good hard puffs (ooh, matron!) suddenly released whatever had blocked it, with an impressively tuba-like accompaniment.

And, reset, it fired straight up.

You, Sir, can award yourself a pint.

[Homeowner Mike]

replying to Adrian, Homeowner Mike wrote: Thanks! I saved a house call charge by reading this. Mine drained from the bottom of a U-bend, I unscrewed the bottom and it was chock full of sludge. Stuck my finger into it and all the water came gushing out! Yea, fixed!! Thanks!

[Brian Gaff]

Ah the stuff of nightmares and fat burgs, which I understand one is now available to view at a London museum. Brian