Where should a room thermostat be positioned?

A room thermostat is a single temperature sensor deciding for an entire building. Everything about whether the heating behaves sensibly depends on whether that one point is representative.

What you'll need

• A tape measure
• An electrician if the thermostat needs moving or rewiring

Step by step

1. Choose a representative room.Traditionally the hall, because it is central and connects everything. A living room works if it is genuinely the room whose comfort matters most, but it is affected by cooking, sunlight and occupancy.
2. Fix it about 1.5 metres above the floor.High enough to be out of floor draughts, low enough to be in the occupied part of the room. Very high positions read the warm air near the ceiling.
3. Use an internal wall.An external wall runs cooler than the room, so the thermostat under-reads and the house overheats.
4. Keep it away from heat sources.Not above or beside a radiator, not near a lamp, a television, a router or an airing cupboard. Any of those satisfy it early and leave the house cold.
5. Keep it out of direct sunlight.A patch of winter sun for an hour a day will shut the heating off in the middle of the coldest part of the year.
6. Keep it away from draughts.Beside an external door, under a letterbox or in a through-draught, it reads cold and runs the boiler continuously.
7. Do not enclose it.Behind a curtain, inside a cupboard, or with a coat hung over it, it reads its own microclimate. This is more common than it sounds.
8. Check what happens in that room.A hall thermostat next to a radiator with no TRV is fine; one next to a radiator with a TRV that someone turns down is not.
9. Consider a wireless thermostat if the position is wrong.Many modern controls have a wireless sensor that can simply be moved to a better spot, which avoids rewiring.
10. Get any rewiring done professionally.Moving a wired thermostat means altering fixed wiring. That is an electrician's job, and in some positions it is notifiable work.

Tips

• If the house is always too warm, look for a heat source near the thermostat. If it is always cold, look for a draught or sunlight.
• A wireless thermostat can be moved around for a week to find the position that behaves best.
• Whatever room it is in, that room's radiator should not have a working TRV.

Common mistakes

• Mounting the thermostat on an external wall — The wall surface and the air near it run cooler than the room, so the thermostat under-reads and keeps calling for heat. Every other room overheats.
• Placing it in a room with an open fire or a wood burner — When the fire is lit, the thermostat is satisfied and the rest of the house gets no heating at all, which is exactly backwards.

If it doesn't work

Questions people ask