Hi, I have a Potterton Suprima 50 that was constantly locking out. The upgraded PCB sorted that problem but now I have anew one! The central heating works fine but I can't always get hot water - when you switch on the call for hot water, the boiler switches on and off constantly as though it's sensing that there is enough hot water. The only way I can get it to stay on for about half an hour is to run the central heating for an hour beforehand. Any advice would be appreciated. Thanks in advance.

Tim McNally, July 2008

Anyone with a Potterton Suprima lockout problem - change the Thermister first £12 (simple clip and two wires). If the problem persists then change the PCB which now comes inclusive of the whole control set (printed circuit board (pcb) kit 5111603). This is much more reliable than the old PCBs (£140 to £180 depending on where you get is from). If instead you replace it with a reconditioned old PCB you'll get the same problem in a years time! With the new control set, make sure you get some instructions as it will look a little different than the old one.

Rob Crawford, May 2010

Turns out it was a problem with the Electronic Programme Unit - replaced it with a unit from Ebay and whilst replacing found a dodgy connection in the wiring at the back.

Tim McNally, July 2008

...just a couple more things that may help diagnose my problem - I've replaced the Thermistor and overheat stat.
Also, when the boiler lights for HW, it stays on for a few seconds (unless I've previously run the CH). The lights on the board then go to flashing green (boiler temp control satisfied) for 2 minutes and then to continuous orange (no external call for heat).

Tim McNally, July 2008

Thanks for this Iain, - I've crudely checked the zone valve - pretty sure I only have one. When I switch to HW the valve lever moves and the pipe to the HW tank gets hot. I guess this would indicate it's working properly?

Thanks,

Tim McNally, July 2008

my first visit would be zone valve motor

iain, July 2008