Worcester 9.24 won't shut off

[zenmonkey]

Hi everyone, first time posting here. I have a 16 year Worcester 9.24 electronic which has recently developed a fault. A few days ago I noticed the CH wouldn't shut off. I've disconnected the external timer/stat and tried using the front panel switch but still can't shut off the CH. I can use the switch to turn off the hot water though.

The relay is soldered onto the board, so I can't check it. So I'm guessing I need a replacement controller board? Or is there anything else I can try?

If I do need a new board, does anyone have any recommendations for a supplier?

Thanks

 

[Agile]

There are so many possibilities and the PCB is only one of them.

I assume you mean the boiler carries on running the CH. In that case I would expect its not very likely to be the PCB but external controls at fault.

Needs checking.

Tony

 

[zenmonkey]

Hi Tony, yes, you have understood correctly, the central heating won't shut off. It's running constantly to keep the rooms at a set temperature. The only control I have over it is the built-in thermostat, which is working as expected. The front panel switch does not affect the CH, only the hot water.

Any idea what external controls off the board would cause this symptom?

 

[spraggo]

I suspect that you have a frost stat fitted, possibly external.

 

[Agile]

Is the boiler fitted in an unheated area like a garage with a froststat nearby?

They look like a roomstat without any visible dial usually.

Tony

 

[zenmonkey]

No, the boiler is in a bedroom and to my knowledge there are no external devices. I can't see any wires running from the casing apart from the mains electricity feed and the timer/room stat I fitted myself (currently disconnected).

I understand the logic, a frost stat would presumably be designed to override the front panel switch to protect the boiler if the property were uninhabited. Could the board have developed a fault causing it to detect such an input? Does the frost stat present a pair of relay contacts to the board like a room stat? If so, are these NO or NC contacts? How would you fault find in this situation?