Boiler ignition problem after powercut

[daviejam]

Hi folks. I have a kingfisher CF 55 outdoor (old) boiler which has started playing up.

After a power cut the boiler will not ignite by itself.

I have checked all fuses & checked that thermocouple tip is located in pilot flame. The thermocouple was replaced by an engineer a year ago.

The boiler lights fine when I do it with matches and all the covers are replaced in front of the boiler. It seems that when the house reaches the right temp. the boiler cuts of the flames but is not able to ignite later on.

This is pure guess work by me however.

All help is greately welcomed as its SNOWING outside again!

David.

[Dave Plowman]

I'd say the likely cause is a partially blocked pilot light jet causing the flame to be too small to activate the thermocouple. Remove it and give it a good soak followed by a scrub in hot water with washing up liguid. Use an old toothbrush or similar.

[BigWallop]

If it's lighting the burner when you put a match to it, then it sounds like the thermocouple has gone faulty again.

[daviejam]

Thanks.

I'll try to clean it up and if that fails then I'll get another thermocouple in there.

thanks for the help folks.

David.

[Ed Sirett]

We (I actually) need to establish whether 'lights fine' means you can light the pilot with matches OK or you can light the main burner at full rate with matches.

The former is OK and I suspect that there is probably a marginal pilot/thermocouple problem when the boiler gets hot.

The latter would be a very dangerous condition, I don't think you mean that though.

[BigWallop]

That's what I was trying to get at, but my wording is wrong. I wanted to know if it was the main burner that could be lit with a match.

[daviejam]

Sorry for the delay in returning the post.

I can ignite the pilot with matches.

What happened the other day was that the light didn't go out. It was a dodgy shade of orange tho. I left it with the intention of cleaning it when the wether permitted me to get in there with the tools to remove it.

When I returned a day or two later the flame was steady & blue. I guessed that something must have been blocked in there and so if this happens again it should just be a matter of cleaning it.

thanks for all help guys.

Davie.

[Martin]

This comes from many years experience nursing a temperamental Johnson Starley WAU, so if it doesn't apply, just ignore me.....

There should be an air inlet at the base of the pilot assembly, when this becomes obstructed (by dust etc) the pilot turns from blue to yellow, (due to oxygen starvation?) then if the restriction gets worse (more dust) eventually goes out and won't re-light. If you know where the air inlet is, just give it a quick suck from a vacuum cleaner (with everything shut-off first).