Potterton Profile thermostat dial slowly moves,turns off

27 Oct 2012
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United Kingdom
Hi all-

I have a Potterton Profile boiler which has been working fine but now turns off by itself when using the central heating. Room thermostat set to max, controller set to 24hr constant for central heating, off for hot water. If I set the dial on the boiler to 3 or 4, the boiler fires up, hot water goes to the radiators. Over a period of time (hour or two) the dial slowly goes down to 1 and the boiler turns off. If I move the dial back to 4 the boiler turns on again.
Is this a normal function to protect the boiler if it is overheating i.e. fault is elsewhere, or is this due to a thermostat fault?
I have bled the radiators, pump and fan seem to be working.
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Are you saying the boiler thermostat knob turns itself off? as in the dial turns from 4 to zero on it's own accord? , suggest you contact the local priest for an excorcism. :eek:
Yes, i set it to 4 and the boiler fires up. After a couple of hours the boiler switches off even though I have set it to run constantly and the the dial is now at 0 (or close to it). If I put it up to 4 the boiler turns on again.
I wondered whether the boiler is overheating so the thermostat is turning it off and setting itself back to 0, or whether the thermostat/dial is faulty and slifding back to 0 by itself and hence turning off the boiler.
Any thoughts?
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Only other solution would be to change the thermostat (RGI needed for that due to having to go into the combustion chamber).

Would love to see a time lapsed vid of this happening though.
Ha ha well if you dont have a ghost the only thing I could think of that could possibly cause this is that the thermostat control rod is extremely loose and that vibration from the boiler is causing it to turn itself off , it should never move by its own accord, set it at 4 and place a strip of sticky tape of some sort accross the control knod and stick it to the surface plate to stop it moving and see if that stops your problem, if it does then you need a new boiler thermostat or just leave it taped up wont do any harm
OK thanks- wanted to make sure I wouldn't do any damage by stopping the dial turning back to 0. I'll try a bit of sticky tape.

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