Potterton Promax FSB Overheating

[ianmcd]

As already said cant see what the difference would be on HW or CH, the boiler doesnt know what it is heating, it just knows there is a demand, wait untill the combustion seal is replaced and see what happens, It could and I mean could be that the burner is staying on longer for CH than when it is HW, and more products are leaking from the CC but without seeing it I dont know

 

[GraRob]

As already said cant see what the difference would be on HW or CH, the boiler doesnt know what it is heating, it just knows there is a demand, wait untill the combustion seal is replaced and see what happens, It could and I mean could be that the burner is staying on longer for CH than when it is HW, and more products are leaking from the CC but without seeing it I dont know

So the CC door seal had partially disintegrated, on the top left side. Looked ok, but crumbled when touched. Engineer fitted a new seal, cleaned & hoovered the burner & HE fins etc.

Seems to be working fine now, so fingers crossed.

Outstanding diagnosis by Ianmcd thanks. Really appreciate you taking time to provide help & advice.

I hope this thread is useful for anyone with the same problems.

Incidentally, the engineer left the thermostats & thermister that was replaced. All checked with a meter & now stored with the boiler documents for the future.

 

[ianmcd]

So the CC door seal had partially disintegrated, on the top left side. Looked ok, but crumbled when touched. Engineer fitted a new seal, cleaned & hoovered the burner & HE fins etc.

Seems to be working fine now, so fingers crossed.

Outstanding diagnosis by Ianmcd thanks. Really appreciate you taking time to provide help & advice.

I hope this thread is useful for anyone with the same problems.

Incidentally, the engineer left the thermostats & thermister that was replaced. All checked with a meter & now stored with the boiler documents for the future.

We are here to help, thank you for letting us know the outcome