Myson Apollo Fanfare 40si

[wclark1238]

Yesterday my boiler started to 'act up' and I was hoping that I might get some troubleshooting tips from some people cleverer than I.

When calling for heat (or indeed hotwater) the boiler fires up as normal and runs perfectly for several minutes. Once things start to get warm it then starts behaving erratically. Specifically it 'cuts out' (in that the main burner goes out). The pump and fan continue to run and then a short while later the main burner relights and things work as normal for another little while before the cycle repeats. The frequency and duration of these 'cut outs' is not consistent. Sometimes the the main burner will go on and off once every 3 or 4 seconds but other times it may stay off for 15 seconds etc.

My first thought was that the issue was to do with the low (or indeed high) thermostat having failed but the problem persists regardless of whether the 3 position switch is in low or high position.

My next thought is that it could be the overheat thermostat but, I would expect that if that was causing the issue then the time between it 'tripping' and resetting would be much longer than I'm experiencing.

Pump is definitely running and the thing does warm the rads (and/or the hot water).

I'd be grateful to hear any other bright ideas.

Thanks.

 

[Agile]

Sounds as if pump is not creating enough flow.

That can be the pump or a blockage or a blocked pump impeller.

Tony

 

[petit_pablo]

When was the boiler last servicd?

 

[wclark1238]

When was the boiler last servicd?

April 2013

 

[Agile]

Was that a PROPER service involving opening the boiler?

Or just a flue gas analysis ?

Tony

 

[wclark1238]

Was that a PROPER service involving opening the boiler?

Or just a flue gas analysis ?

Tony

Full monty. Burner out, little nifty hoover thingy applied to every nook and cranny........

Either those smarter than me think that the guy who serviced it broke it but it's taken 6 months for that to show up or there's some other reason for such avid interest in the servicing of my boiler.

As for the first response regarding a pump issue, thanks but I've eliminated that as a cause. It's working quite happily still drawing the usual 70w and making no unusual noises. Equally it is performing well enough to get heat out to all of the rads.

 

[Agile]

I don't think that the fault is caused by the service.

Are you capable of safely measuring the voltage applied to the second stage of the gas valve during the fault condition?

I suspect that the voltage is being lost!

But we are getting rather too close to what I am permitted to say here.

Tony

 

[wclark1238]

I don't think that the fault is caused by the service.

Phew. Neither do I.......I was being a little bit 'tongue in cheek'

Are you capable of safely measuring the voltage applied to the second stage of the gas valve during the fault condition?

I suspect that the voltage is being lost!

I am an electronics engineer by training with expereince working as a service engineer in the pump industry so I can indeed check voltage levels safely. Most importantly I do know my own limitations - as far as I am concerned the MOST important aspect of 'competency' is understanding when one's own experience/knowledge has been exhausted.

But we are getting rather too close to what I am permitted to say here.

Not sure if this will help (you to feel slightly less nervous about disclosing advice) or not but I have previously replaced a fan on this boiler - 18 months ago - but whilst I consider myself 'competent' to do so I am also smart enough to engage the services of my GasSafe registered neighbour to complete the 4 tests after I'd done 'the work'.

He doesn't do servicing usually (installation guy) but for the price of a beer he is happy to help me by completing the tests to ensure that my work hasn't introduced any issues. I've not yet spoken to him about his availability to drink a beer and complete the 4 safety tests once I get to the bottom of things this time (if indeed it turns out to be something that I can tackle myself).

Thanks for your inputs so far. I'll check voltage to solenoid tonight.

 

[wclark1238]

Well, how bizarre. Things have settled right down with, according to my wife, no recurrence of the spontaneous cycling phenomenon at all during today.

I'll keep this thread updated if/when things progress further. Meanwhile, fingers crossed.

 

[wclark1238]

Well, the problem has recurred and I've now done further troubleshooting. As I surmised it appears that the issue is the overheat thermostat. I have (temporarily) removed and bypassed it and the boiler works normally eventually cutting out in accordance with the low or high thermostat.

Now I shall start a search to find a replacement overheat stat.