Heating stuck on, thermostat working

AdrianW2

Apologies if this is has come up before, but I can't find quite the same problem in any of the other CH threads. Our Y design CH appears to be stuck on, regardless of the settings on the programmer.

It's still responding to the thermostat, so is still controllable. I suspect that rules out problems with the plumbing, pump and valve - is that a reasonable assumption?

So suspicions falls to the controller, but that also appears to be working, in that the lights come on and at least one relay inside clicks at the right times. Hot water seems unaffected. I've tried the reset button but it hasn't helped.

Next step is to start poking around with a meter, but I'm not entirely sure how the logic in these things is wired.

Any advice welcomed.

Robbo77

Sounds like the CH motorised valve has failed and is stuck open. When this happens, the microswitch on the valve will continue to operate the boiler, despite your timer being off. Its likely you stat shuts the burner off but the boiler and system will still contine to work. Hope this helps.