Firstly our system is old. Baxi boiler, Potterton controller, hot water tank etc.

We had an occasion last year when the controller turned the system off but the pump continued to run. The only way we were able to turn the pump off was to turn up the thermostat, start up the system again then shut it back down a few minutes later – this shut the pump off.

System was then fine with no issues.

Roll on 12 months and the system has experienced the same problem. The first time was solved as above but this evening this trick didn’t work. Turning the mains supply off shut the pump down but when switched back on the pump started up again and the boiler fired without a signal from the controller! Eek.

Now not sure what to do as the system seems to have a mind of its own.

Any thoughts as to what we could try or are we beyond that now?

Cheers,

Mark

probably a wiring fault, open up the junction box, get you multimeter out and see what is giving the pump and boiler a signal.

Start from the wiring from the motorised valve(s) and work back through thermostats to programmer.

failing that call a friendly professional.

Most likely the Motorised valve either motor or switch inside sticking. Unless you’ve got a frost thermostat somewhere?

Thank you guys.

YP – which valve are you referring to?

We had this problem in our last house and it turned out to be a fault with the motorised valve (in the airing cupboard).

As Stumpy says usually in the airing cupboard not a major job but sounds like you need to get someone in to repair/replace for you.