Alpha 240x combi boiler cutting out

[diezeltruck]

Hi,

I was reading an old thread

The original OP question was

"This is an Alpha 240 x combi, the symptoms are, the burner comes on, for say, 5 secs, either for DHW or heating, and then goes out, then almost immediately, in about 1 or 2 secs, comes back on again. It might stay burning for 20 secs, but then goes off and restarts quickly.
I get the feeling the on/ off cycle is too quick for it to be water temp. related? happy to hear from anyone with more experience"

Several replies were given one by a member called Agile who suggested Air Pressure Switch as the cause of the problem.

A member called Namsag wrote "faulty sensor fitted beside the plate heat exchanger gives those symptons"

Is Namsag referring to differential pressure switch just below and to the right of the DHW heat exchanger?

I replaced the Primary Temp sensor thinking it was that but made no difference.

There is also an overheat thermostat and wondered if this could cause these symptoms.

Would any of you guys confirm your suggestions and whether I should replace the Air pressure switch first and whether I should also replace the differential pressure switch near the DHW heat exchanger

appreciate your thoughts

Thanks

Paul

 

[diezeltruck]

Not that anyone has replied to my initial post but here goes.

On removing the front boiler cover to locate the Air Pressure switch on the Alpha 240X boiler I have discovered that if the cover is sealed tight as it should be the the symptoms described in my OP occur but on loosening the cover the symptoms stop and the boiler continues to fire/burn without randomly cutting out every 10-20 seconds.

If I don't tighten the screws completely then the problem i've been having goes away.

If I tighten the front boiler cover so its 'air tight' then the syptoms come back and the boiler cycles on and off every 10-20 secs.

Now does this suggest definitely a faulty APS or could it suggest a blocked flue or failing flue fan?

Cheers

 

[ianmcd]

you need to clean the fan venturi, you really shouldnt be doing this as you are not registered and you shouldnt be removing the combustion cover or slackening it, this is dangerous