Main multipoint ff

[dave1]

Got this multipoint water heater that locks out randomly. It's two years old and I can't find anything wrong. Correct polarity working pressure 19.5mb.
Works most times, it goes to solid lockout light sometimes and flashes 4 secs on 4 secs off others.
TNT says it even does this even if nothing being used and he is out.

New flow switch and overheat stat fitted, I Bellevue new aps and thermistors also fitted.

Any ideas????

 

[ambrosia]

had a similar problem

stuck and analyser in the flue and it had really high ratio

turned out fan wasnt clearing products of combustion and flame was sufficating

no idea why it would do it when nobody was using it however

 

[dave1]

Thanks ambrosia, stayed there yesterday for 2 1/2 hours reconfigured the pcb and put heat paste on thermistors. Didn't lockout the whole time got a call later to say it was still doing it. Very very strange.