Alpha 240x combi boiler cutting out

[ianshearer]

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'm a computer tech, happy rewiring houses, but little experience on boilers, and I don't mess with the gas side of things
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, thanks in advance. I can check voltages and read the diagram
Ian

 

[Agile]

I expect its gas related so no advice from me other then fan/vent/APS.

Tony

 

[ianshearer]

Thanks Tony, I will see what the APS is doing. took me a bit of reseach to find that "APS"is a Differential air pressure switch, certainly would explain the symtoms

 

[bengasman]

aps is first guess, rectification second

 

[Agile]

I went to a boiler repair yesterday where the installer had suspected the APS because the on board diagnostics showed that. He then blew into the APS to totally spoil it.

He then replaced the APS and of course the boiler still did not work! By then he had spent about six hours on it so he gave up.

The Owner was most sceptical when I came along all smiles and "will soon have it going again for you". He said "I am impressed by your confidence" in a rather disbelieving way!

When I had it working a short while later he was most amazed as he clearly had not expected that I would be able to repair it. I just replied "its what I do all the time".

Tony

 

[Slugbabydotcom]

While you are waiting for MI's
Have a look into your flue to make sure it hasn't fallen apart inside.
Then check out CH temp sensor [if it has one]

 

[megsona]

Ian, have you made any progress with your fault on the boiler? I too have an Ocean Alpha 240E which is doing the same burn for a few seconds, cut out, restart, repeat, type behavior.

I'll tackle most things but boilers are not my forte. Any headway you've made would be welcome.

 

[namsag]

faulty sensor fitted beside the plate heat exchanger gives those symptons.

 

[ianshearer]

I haven't had a look at this yet, it's the boiler at my sons house. Thanks for all suggestions, I will post an update when I have tried again

 

[Andycul]

Hi Tony just wanted know what you did to fix the boiler that seems to have the same problem as mine.

 

[Agile]

Post your own new thread if you have a query giving full model details.

Tony

 

[ianshearer]

Just to finish this thread off, for the sake of anyone doing searches for similar symptoms, the problem got a bit better by itself, so I left it short cycling occasionally, but essentially working.
Recently it packed in completely, refusing to light. cleaning the fan blades got things going again for a week or two, then the not starting at all returned. I replaced the fan, which was looking and sounding a bit tired.
I then couldn't relight the pilot light, and replacing the ign board cured this.
The symptoms now are it will fire up and run for a few hours (CH) then sit with the CH pump running, and no flame. Switching the CH demand off and on again will restart it. I started another thread for this symptom. and somebody has suggested the Primary temp sensor thermistor could be playing up, so that's next on the list to be changed