Location, location, location. I've lost count of the times people have asked me to look at a 'faulty' thermostat but actually there was nothing wrong with it. 8 times out of 10 relocating the thermostat solves the problem. However there are some homes that are tricky to meet all of the criteria. and other adjustments are required. Once downsizing a radiator in the room where the thermostat was located kept the system running a bit longer to allow the other rooms to heat up first.
There are no fixed best places, as to where a room thermostat should go. A hallway may be good if it's cool, but not if it's totally internal, or south facing with a large glass area that is warmed by the sun. Every building is different, so here are the principles that should be considered when selecting a location.
1. The room thermostat should be in a cool area, ideally the last to warm up. That way the other rooms will already be warm enough, (but not overheated because of their TRV’s) before the room thermostat switches the entire heating system off.
2. It should be in a room that is not effected by other sources of heat such as an open fire, cooking equipment, or direct sunlight etc. It should not be somewhere draughty or too close to a window, especially one that is opened in the winter.
3. At least one radiator in the room with the thermostat installed should not have a TRV fitted. Otherwise the TRV can prevent the room thermostat from working properly.
4. The thermostat should be mounted about 1.5 metres from the floor, and not close to, or above a radiator.
5. Preferably it should not be on an outside wall, (although if you have well insulated walls, this is not quite so crucial.)
6. It should be in an area where air can circulate easily, not in a corner, or hidden behind curtains, or furniture.