Ravenheat water too hot.

[PJfixit]

Having found that the c/h has now stopped working I decided to change pcb.
Bought one from Ebay (new) the seller had a good rating so I thought this would be ok.

I installed the pcb, great everything worked until water leaked over the burner!

Dried everything out, could not find anywhere the water had leaked from.
I discovered that with the replacement pcb fitted the boiler fires up as soon as dhw or c/h is selected without turning the hot tap on. That is to say I cannot stop the boiler from firing up unless I turn the selector to off.

With the original pcb (I swapped them back) I can have dhw but no c/h.

Should I conclude that I was sold a faulty pcb of could there be anything else worth checking?

By the way there is no sign of a leak now so I am guessing the problem was with the replacement pcb installed the dhw overheated (as the hot taps were turned off) & perhaps pressure escaped through the air vent?? No sign of water from the pressure relief valve though.

 

[PJfixit]

Further to the above...

I don't like giving up so I decided to keep fiddling.

I disconnected the potentiomiters at the new pcb one at a time & fired the boiler up.

Did this a couple of times & so far the boiler is now performing correctly with full temperature control over c/h & dhw.

I cannot say that I have a conclusive explanation for the saga but at least now we have the boiler up & running.

Thanks again for all input.. except for the skip