Does the flue from a gas boiler need to be swept?

[Phil]

As header really. The boiler installation is an old New World stowaway back boiler. Age unknown but it was here when we moved in some years ago. Still works well and is serviced annually. 2008 the heat exchanger was somewhat clogged with soot. This had been cleared previously in 2007 when it was also somewhat clogged. Over the last month or so the boiler has seen good use and now does not appear to warm the house as it should. I suspect the heat exchanger may be clogged. AFAIK the flue has never been swept. The boiler may be past its use by date but any constructive comments would be much appreciated. Thanks, Phil.

[OG]

It has been a particuarly cold January (coldest winter for 13 years I heard someone say on the radio just now), so the problem may not be with the boiler, but just that its colder outside.

We had our subsidised cavity insulation installed back in December, it seems to keep the inside about a couple of degrees warmer (not a formal measure I know, but hopefully you know what I mean) than before.

Our council are offering a 70% subsidy, worth taking advantage of.

[Fred]

I can't believe that a serviced boiler is creating soot. It really shouldn't be if done by anyone half competant.

[Harry Bloomfield]

Phil pretended :

Producing soot is certainly not normal, it is an indication of the boiler lacking an adequate supply of air.

[The Natural Philosopher]

Or poor installation. Or hort ycling

I used to get this a lot with an unbalanced flue..

[Tim Downie]

Although he doesn't say, I suspect that this is not a room sealed boiler so the "soot" could just be burnt fluff etc. that gets drawn into these boilers rather than an indication of incomplete combustion.

Tim

[YAPH]

If the heat exchanger has got sooted up the flue should certainly have been be checked for soot deposits (and any removed) before it was put back into service. The /cause/ of the sooting up should also have been ascertained - especially if it's happened twice! Whether that's inadequate ventilation, inadequate flueing, wrong gas injectors or whatever, two sooting incidents in 1-2 years indicates that something needs fixing, urgently.

[Ed Sirett]

This is the sort of boiler that just could possibly do you or someone else some harm. There is a reason for the soot build up and it is certain that the cause remains.

CO production will now be certain, and if the flue gases are not going up the flue where will they be going....

[Fred]

Those are my thoughts as long as the OP is really OP is seeing soot. Are there many instances where a service engineer would leave a boiler in such condition?

[YAPH]

I can think of one: that he leaves it cut off from the gas supply with a warning notice attached that it is "Immediately Dangerous".

[Fred]

My thoughts from the initial post. Either that or he'd have fixed it. Shame the OP hasn't come back. I can only assume the OP's been servicing it himself.

[Andy Champ]

Took me a while to get that one. You need a supercharger.

Andy

[Ed Sirett]

Very likely. There seems to have been treatment of the symptoms of soot rather than their cause.

Most likely the causes are (but not limited to) lint on the air intake gauzes, debris/lint on any part of the burn injector, mixing tubes, or burner bar, wrong gas pressures, flaming back to the injector. The list could go on an on, once soot builds up it makes things worse. This boiler is an accident waiting to happen, I hope no one is currently using it.

The flue liner could be the problem but that would be determined in a service with smoke matches (smatches) and a smoke pellet test.

[Phil]

Lacking an adequate supply of air or lacking an adequate exhaust facility?

[Phil]

Que?

[Phil]

Thanks Tim,

certainly not a room sealed boiler. Your suggestion may be a possibility.

[Phil]

Thus my OP. Induction is good, exhaust is as yet unknown.

[Phil]

Well, I don't know the definition of soot but the fins in the heat exchanger were clogged with a very fine black substance. Finer than talcum.

[Phil]

Thank you. BG applied such a warning notice some years ago. They then came in to put it right and issued a certificate saying that it was fir for use. Said boiler maintained by them since.

[Phil]

Not any shame at all, I don't live on the pc. I have not ever tried to service this myself and would never do so. Your assumption is entirely incorrect and more shame to you. I use the services of professionals. Costs a great deal of money and seems to get me nowhere.