Worcester Bosch 30CDI I think, not mine.
Boiler continuing to run when heating and hot water service switched off.
Assuming this is not the frost stat. what is a likely cause?
Zone valve micro switch?
Cure?
regards
Tim Lamb explained :
Boiler stat?
What do you mean by "boiler running"? My ancient WB 280RSF will sometimes run the fan (but no gas or ignition) when it's very cold, even when otherwise off. Unless you look through the window, it sounds like it's running.
Not that. No heat selected overnight but radiators still warm the following morning.
regards
In message , Harry Bloomfield writes
Probably not actually a 30CDI. The owner can't remember:-)
It is cycling on the boiler stat. OK.
regards
>
If it's an S-Plan system (separate 2-port valve for each zone) it's probably a zone valve microswitch failed in the 'on' position. It won't be immediately obvious which actuator's switch has failed because they're all wired in parallel. Try a bit of light percussion on all the actuators in the hope of unsticking it. If that fails, you'll need to disconnect the orange and grey wires of each actuator in turn from the wiring centre and see which ones are shorted. You'll then need to replace the offending microswitch - or even the whole actuator.
If it's a heating zone whose switch is faulty, as a temporary measure you could nick the actuator from the HW zone (assuming they're all the same type) and use an immersion heater for hot water.
In that case, what I wrote earlier may not be correct because the zone valve must actually be open for the radiators to be hot - and it wouldn't be if just its mircoswitch had failed.
Sounds more like a room stat has failed shut regardless of demand - unless a zone valve has physically seized in the open position. When this problem happens, is the zone valve's manual lever floppy - like it is when the valve is open? Does the valve close if you remove all power to the system?
Unfortunately the owners are in transit: staying with us overnight for a taxi service to Heathrow very shortly!
The boiler is 30 miles away and unattended.
I am hoping to pass on sensible suggestions to any attending plumber. The above looks testable.
Thanks
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