Central Heating Intermittently Staying On

[chrisctk]

Hi everyone. I am stumped - for some reason my central heating intermittently stays on even when the room thermostat tells it to turn off. I have checked the wiring the the thermostat call drops to 0v correctly when its meant to turn off, and 80% of the time the heating will turn off fine within a few minutes, but 20% of the time the heating stays on.

I am no expert with central heating, but following the wires it looks like the thermostat effectively controls the mid position actuator (BGMVSP-23), could it be that this is faulty?

Any tips??

Thanks!!

 

[jackthom]

It is possible that the 3 way valve actuator is sometimes sticking leaving the central heating port open and the boiler is occasionally firing up as normal because there is a call for heat from the hot water cylinder thermostat.

It could be a duff actuator, which sits on top of the valve assenbly, or the actual valve itself may be gunged up and stiff.

 

[chrisctk]

Thanks for your reply. Is there anyway to test / fix, or is it a case of popping to screwfix for a new unit?

 

[jackthom]

The actuator part can be opened or removed so you can look at what it's doing as it operates. Beware of mains voltages inside though.

After lifting off the actuator you should also be able to see if the valve itself is free to move (it doesn't rotate far, much less than 90 degrees).