Potterton boiler - heating / lockout

[mikeregan1]

We have a Potterton Combi 80 boiler.

Problem:
Running hot water leads to radiators heating up, despite the central heating being turned off (but this doesn't happen every time the hot water is run). After a while of heating up the boiler locks out.

About 9 months ago we replaced the diverter valve and PCB which fixed the problem but now it's returned and our engineer has told us the diverter valve and PCB look fine.

Any suggestions please?? Thanks

 

[Gasguru]

Was the whole diverter valve replaced or just the front section?

 

[mikeregan1]

Thanks for the quick reply. I believe the entire valve was replaced.

 

[Gasguru]

Are you sure the radiators are heating up when the hot water is being run? If so the diverter may be contaminated with system debris preventing the flow port to be fully closed or partially sticking.

The tops of some radiators may get slighly warm after several hotwater draw offs due to pump overun.

 

[freeflow]

there should be a external bypass fitted to this boiler,has it been closed?
this would give the problems you are describing.

 

[mikeregan1]

The radiators are definitely heating up.

When we turn hot water on this triggers the green 'flame' light as expected. Problem is sometimes when we turn the hot water off the flame light stays on (and you can hear the boiler working) and heats the radiators up until they are red hot, after a while the lockout light then comes on.

When I see the flame light staying on I switch the boiler to standby in order to turn it off. If i turn it straight back on the flame light come straight back on the radiators keep heating. If i leave it on standby for 15 mins before turning on again the problem seems to be fixed.

Can you please elaborate what you mean by an external bypass? Is it easy to check?

Thanks again for your help

 

[Rob]

Remove the front white cover. On the PCB you'll see a red LED. This indicates there is a Hot water demand. If it stays ON after the tap has been turned off you need a new flowswitch and microswitch.;

 

[Gasguru]

Problem is sometimes when we turn the hot water off the flame light stays on

Helps if you explain the problem properly in the first place

 

[mikeregan1]

Thanks for your help, looks like it was the micro switch.