I've got a Honeywell CM thermostat (which is a slightly updated CM67). I've found that the heating sometimes comes on when the room temperature is above the target temperature. This has happened 4 or 5 times in the last day or so (maybe as the heating's been on more than usual).
For example this morning at one point the target temperature was 17.5 deg C. However the thermostat triggered & when I looked at the thermostat (a few secs after it came on ) the room temperature was 18 (& had been 18 or 18.5 for the previous half hour or so).
Is there something weird going on - or is it just the proportional bandwidth working itself out?
Michael
PS I'm not using the optimisation feature.