Potterton CH and HW control problem

[draftdodger1]

I have a Potterton system that is a Suprima Boiler with Programmer, Room Stat and Frost Stat. All works normally with a period in the morning and evening that the system runs. The problem is that about 4 hours after the system has closed down as dictated by the Programmer the CH system runs for 10 minutes and then shuts down. The 10 minute run is not activated by the Programmer as this remains off but the Room Stat comes alive, the CH Zone Valve opens, the Pump runs and the Boiler lights up. Then 10 minutes later it all shuts down until the next programmed session. Its all a bit strange and the programmed sessions are all normal.

The System is about 5 years old and as a result of the problem I have changed in order the Room Stat, the Programmer, the Frost Stat and the Zone Valve motor. I have not changed the PCB in the boiler which I know can give problems in the Suprima.

The time after the programme stops to when the 10 minute session starts is about 4 hours but not exactly and slightly different every time so it does not appear to be activated by the programmer (which does not activate anyway). Likewise the 10 minutes it stays on is slightly different every time.

I am at a loss as to why it happens but the system becomes live when switched off. Any ideas would be appreciated. Maybe the PCB is the problem, I thought the Frost Stat (but have changed it), maybe the system is wired up incorrectly but what sort of faulty wiring would cause such a problem.

Anybody out there with any ideas, many thanks in advance.

DD

 

[gas4you]

I would expect to find that the system has been wired up incorrectly in the wiring centre.

The pump over run, controlled by the pcb, sounds as if it has been wired to possibly the brown wire going to the ch 2 port valve, thereby turning the ch on when ever the pump is working

 

[draftdodger1]

Thanks very much gas4you. I am still puzzled why it only happens 4 hours after the programme has finished and then for only 10 minutes. If it is wired incorrectly I am still bemused as to why is does not happen all the time.