Hi, I am not an electrician but am quite good with electrics and wanted some advice before calling out an electrician to work out what is wrong with our room thermostat. I have a Main HE Condensing Boiler and three room thermostats that operate different parts of the house, which has been extended a few times. There is also a Drayton Lifestyle LP722 dual channel programmer for hot water and heating next to the boiler. Two of the heating thermostats work perfectly, i.e. when the timer on the LP722 is off for heating the thermostats have no effect. The third thermostat works differently. It comes on during the night (sometime after 3am) and during the afternoon (just before 4pm) if the temperature dial is low enough for it to come on. I am wondering how this can be. The heating and hot water are off between 11pm and 5:50am, so it seems this has no effect on the third thermostat. All three thermostats are of the old fashioned type, turning a dial to the desired temperature. The third thermostat is a Honeywell 4200 (looks quite old). I would really appreciate if anyone could help in telling me why the third thermostat can operate in this way.