suprima boiler fuse

[SparkyTris]

I have a Potterton suprima boiler which keeps blowing the 3 A fuse on the boiler PCB.

anyone got an intimate knowledge of the suprima PCB? what circuits does the onboard fuse protect?

The problem occurred naturally, after a fairly extended period of not using the CH system at all.

The problem does not appear to be the board (have tried 2 boards, both produce same fault),
it's unlikely to be the circulating pump (wiring checked & pump spindle turns freely)
it doesn't appear to be the gas valve (meters OK)

 

[undercover]

Have you 'metered' the fan

 

[Agile]

Most likely to be the pump!

Try supplying it from a seperate source fused at 3 A.

Could also be water in a motor valve.

Tony

 

[gas4you]

I would go for the pump first. Remove the pump live from boiler terminal, turn boiler back on. If fuse doesn't blow then it is the pump

 

[SparkyTris]

wise words, thanks for the quick posts. The plot, as always, is thickening.... apparently the boiler case is showing 240V wrt earth.
there has in the recent past been a bit of "rewiring" done in the vicinity of the boiler and/or pump, possibly a loose earth somewhere...

sounds like this one might be an amalgamation of a "simple" CH fault which has now been combined with a wiring fault....

fan aint been checked yet, but turns nicely and smells good. I feel that once the unearthed case has been fixed the pcb fuse will stop blowing and peace will be restored to the universe.

 

[gas4you]

Case is probably earthed through pipe work or fan anyway. You should be looking for the cause of it being live, not just getting the case earthed

 

[SparkyTris]

know what you mean but... case is not LIVE live, just reading 240V with a fluke. Well, at least I'm assuming that it's not live live as it hasn't given anyone a belter yet.