Blocked condensate pipe

[Ben Blaukopf]

Woke up this morning to find a d1 error - condensate pipe/trap blocked on my Vokera. Frozen, obviously - except it couldn't be, because it routes to an internal waste stack. I extracted the pipe and trap from inside the boiler and found the pipe blocked with a load of black gritty gunk (which apparently is due to the condensate dissolving the aluminium heat exchanger?). Cleaned that out, still didn't work. Faffed around a bit, and it started working, presumably because some condensate higher up had finally cleared the sensor. Put it back together, working boiler :)

So ice isn't the only problem. Question is, is this level of blockage normal? Or is my heat exchanger on its last legs?

[Andrew Gabriel]

My (Keston) runs at low temp - typically 45 flow, 32 return. I have had a couple of cases of something slimy/jelly-like growing in the bottom of the heat exchanger, and blocking the drain hole. You will get a build up of burned insects and the like there, which were sucked in the air intake. If you run the boiler at very low temperature like I do, this can form the basis for some organic growths, and even if you don't, that debris itself can block things if it builds up.

To clear out debris which collects in the bottom of the heat exchanger before it builds up enough to block the outlet, I now pour a couple of pints of water into the flue terminal a couple of times a year, which with my Celcius 25 does result in washing away any solids collecting on the bottom of the heat exchanger, and it hasn't blocked for some years now. I don't know if this is safe for all condensing boilers (but certainly don't make a mistake and pour it in the air intake - that's probably rather fatal in most cases). However, it's a lot easier that taking the burner off the top of the heat exchanger and flushing through with water, which is what the service instructions expect you to do (and always requires a new gasket, as a new gasket breaks into about 20 pieces the first time you fire up the boiler).

[Ben Blaukopf]

Ta.

In the "faffed about" stage, I was reading the bit in the manual about the heat exchanger and replacing seals, and deciding that was a step too far.

I presume that if I simply identify which bit of the flue the plume is coming out of, I'm unlikely to go far wrong, provided it doesn't run downhill to the outside!

[Andrew Gabriel]

Someone familiar with the insides of your boiler would need to comment on that - I'm not.

ISTM it shouldn't do any harm because condensation in the flue needs to run back into the boiler anyway and be drained out, but that path might not flush the base of the heat exchanger, and might not be able to handle more than a tiny trickle in all cases.

[newshound]

Presumably with the "concentric" flues, the vent is always on the inside with the intake as the annulus

[David.WE.Roberts]

If I understand what is going on (which is questionable) when my Worcester Bosch combi is first powered up it runs in a special low temperature mode and also primes the condensate drain.

So perhaps all I would need to do was power off then on again every 6 months or so.

Cheers

Dave R

[meatloaf]

Woke up this morning with water dripping from my sabre boiler, took it apar t and found that water was somehow getting into the combustion chamber,chec ked condensate trap and it was empty ,stripped out condensate pipe back to the Condensing unit it was blocked solid with ash like grit, Condensing uni t itself was blocked as well and full of water cleaned them all out and boi ler returned to normal operation