I have a pumped, vented, Gas CH / HW system with a room stat, boiler stat, electric programmer and two two-port electric valves that sit in parallel with each other - one does HW and the other does CH.
We noticed the pump and boiler have been coming on at funny times, or not going off at the end of the day like they should.
Valves seem to open / close fine.
I have currently removed the programmer from the wall AND un-wired the electric valves, but the pump is STILL running. Boiler is off. If I turn it all off at the wall the pump goes off, but as soon as I power it on again the pump restarts.
The only way to stop the pump is to manually operate the vales open (as they are currently disconnected) which allows the water in to the CH / HW circuits. Presumably this drops the water temperature and the pump eventually goes off.
So, I think there must be another thermostat somewhere in either the boiler or the pump (or both?) and this is causing the system to keep running somehow.
Any tips on troubleshooting please?