How to install a semi-recessed thermostat

Where the thermostat goes matters more than how it is set

A badly placed thermostat makes the installation work against itself. Avoid: a wall that faces outside, a through corridor, directly above a cabinet, immediately next to a door, and any spot the sun reaches late in the day. The sensible compromise is an internal wall, about a metre and a half up, in the room whose comfort matters most.

The opening

A hole saw with a 67 mm cutting diameter is enough. The depth needed is that of the back box, worth checking before cutting, particularly on an insulated lining where the vapour barrier must not be pierced.

Wiring and finish

Fix the box, make the connections, then push the unit into place. Semi-recessed fitting leaves the housing slightly proud, which absorbs the flatness defects of an older wall without being visible from the front.

The commissioning that follows is described on the page about the radio and wifi receiver, and removal, should it be needed, on the one about the mounting plate.

Semi-recessed or surface: what decides

Semi-recessed calls for a box in the wall, which assumes you can cut without meeting a conduit or piercing a membrane. In light renovation, on a thin partition or on a stone wall, surface mounting avoids a risky opening for a result that still looks clean.

The height, and why it matters

A metre and a half is not an aesthetic convention. Lower, the unit reads the cold air creeping along the floor and overheats the room. Higher, it reads the warm air gathered under the ceiling and underheats. That height is the compromise that reads closest to what a person sitting or standing actually feels.