I have an ageing Thorn M Type boiler, what I have noticed is that the boiler seems to run OK but if I turn it off via the programmer (by moving the selector switch to off) whilst it is still lit the boiler continues to run until the water in the gravity fed system overheats and turns my loft into a tropical paradise. At first I suspected the boiler thermostat but as long as mains power is fed to the boiler the thermostat functions properly i.e. if I turn it off the boiler stops, and it also "cycles" normally. I am assuming that the gas control valve requires a mains feed to shut itself off. Is this correct? My concern is that in the unlikely event that the electricity gets cut when the boiler is running then it will continue running until the boiler melts down.
Thorn M Boiler Wont Stop
- Thread starter MarkPG
- Start date
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I've already tried unplugging it but the boiler keeps on running.
As for the sticking gas valve, I thought that but it works O.K when the power is on, since when I turn the thermostat down the gas shuts off, and the boiler cycles ok on its own. How does the valve return to its off position does it use a spring?
As for the sticking gas valve, I thought that but it works O.K when the power is on, since when I turn the thermostat down the gas shuts off, and the boiler cycles ok on its own. How does the valve return to its off position does it use a spring?
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Yes. Gas valve with no power should close.
Possibility:
You may have power supplied separately to a motorised valve switch which supplies power to the boiler. The motorised valve could be powered from the programmer via the thermostat(s).
If the valve is driven shut (when your programmer power is ON) then the switch is opened and the boiler supply goes off. If the valve is open (switch is closed) and the programmer power is turned off, the boiler stays on because the switch is supplied separately.
See?
Possibility:
You may have power supplied separately to a motorised valve switch which supplies power to the boiler. The motorised valve could be powered from the programmer via the thermostat(s).
If the valve is driven shut (when your programmer power is ON) then the switch is opened and the boiler supply goes off. If the valve is open (switch is closed) and the programmer power is turned off, the boiler stays on because the switch is supplied separately.
See?
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