Came back after a night out to find the house very hot indeed.
Had a play with the thermostat (set to 18degC) and it clicked at 27degC. So whatever the system's doing it isn't reacting to inputs from the thermostat.
I've turned the radiator water temp down at the boiler, which means the house doesn't get quite so uncomfortably hot but we don't have to sit there and shiver either (the house is also our home office so we're around a lot of the time)!
System is an Ideal Classic RS260 boiler, Landis and Gyr heating control panel, Honeywell junction box, Honeywell thermostat, Honeywell 3 port valve (replaced in Dec 2010 due to sticking on the hot water setting).
Any tips on diagnosing the problem? The obvious suspect is the thermostat, but are there any further areas to look into before I go and buy one?
Had a play with the thermostat (set to 18degC) and it clicked at 27degC. So whatever the system's doing it isn't reacting to inputs from the thermostat.
I've turned the radiator water temp down at the boiler, which means the house doesn't get quite so uncomfortably hot but we don't have to sit there and shiver either (the house is also our home office so we're around a lot of the time)!
System is an Ideal Classic RS260 boiler, Landis and Gyr heating control panel, Honeywell junction box, Honeywell thermostat, Honeywell 3 port valve (replaced in Dec 2010 due to sticking on the hot water setting).
Any tips on diagnosing the problem? The obvious suspect is the thermostat, but are there any further areas to look into before I go and buy one?