i have a glow worm ultracom 12hxi heat only boiler which has an expansion system not an f and e tank,only i cannot switch off the central heating mode unless i turn off the boiler at the switch spur,it will not turn off when it has reached temperature,

big al 21, December 2011

big al 21, if you have a room stat check for a little 'click' when you move the dial if not could be that its stuck on demand, if no r/s could be time clock has shorted-out, lest likely is boiler stat gone (if heating pipes are boiling hot )

hope helps

Tim, December 2011