About once a week my potterton suprima 60 CH goes mad and gets hotter and hotter. If i click the CH room thermostat down it keeps going, if i turn the CH off on the timer it keeps going. The only way to stop it is to power the boiler and timer off and back on, then its fine until the next time.

any idea whether its the boiler, timer, or thermostat?

Tim, January 2007

i havent tried the thermostat, I will try it. Where are the zone valves, in the boiler or do you mean the valve in the airing cupboard?

Tim

Tim, January 2007

can I assume it goes off when you turn the boiler stat down?
if it does as I suspect it will be one off your zone valves sticking - possibly the micro switch inside

Paul the gas man, January 2007