The gas central heating system does not always switch off. The electronic timer switches the heating off but the central heating pump still runs and the gas boiler cycles on and off. the wall thermostat has no effect.
At the moment this is happening at night (uncomfortable sleep) but can happen in the day. the electronic timer has recently been replaced but this fault was there before.
you don,t say what system you have ie combi, or more likely standard boiler with three port valve for heating and hot water. if so valve may have stuck . another possibility is if boiler is in outhouse or garage is there a frost stat fitted?
give us a clue...........
The boiler is a standard gas boiler, not condensing or combi, about 7 years old on a three port valve for heating and water. There are thermostatic valves on all radiators and more than one is open fully. The boiler is located in the kitchen. My initial suspicion was a stuck valve but it seems to follow a pattern of night time and certain times of the day.
try: when house cool turn cylinder stat down to make sure it's not calling boiler, then with ch on prog. set to on room stat should turn boiler on and off, note pump may run on for a while after boiler shuts off this is normal so check at boiler not pump.
if no control suggests room stat u/s