Help! Ideal system boiler failed for Xmas

[Joe Malone]

Can anyone shed any light on this please. The boiler failed yesterday and we managed to get a gas engineer yesterday who diagnosed and changed a faulty fan. The boiler started back up but appears to be 'hunting', at least this is the term I'd use, being an ex car mechanic. WE turned the boiler back off last night due to this problem and can't seem to get hold of the engineer today. Can anyone explain what causes this problem please? The boiler seems to speed up and slow down at regular intervals as though the gas supply is fluctuating.
Thanks in advance.

 

[spraggo]

You do not mention the boiler details, model No etc, but one cause of this could be lack of flame stabilization due to your RGI not sealing the combustion chamber door correctly, which should be rectified immediately.

 

[Joe Malone]

Thanks Spraggo, that makes perfect sense to me. Its an Ideal classic, the RGI had to remove the heat exchanger from the top to get at the fan. There was a hood which was removed which has a sealing gasket round it. Could a poor seal on this hood gasket cause what you describe?

 

[Joe Malone]

Incidentally; we've got hold of the RGI and he's coming back this afternoon. Fingers crossed!

 

[spraggo]

Yes this could cause flame vitiation (lack of oxygen), the flue and combustion chamber must be completely sealed.

Regards
spraggo

 

[Joe Malone]

He's been, it's fixed, you were 100% right. Thanks again.