A corner is a weak place for a wall split. The jet curls back into the return, the unit short-cycles, the nearest chair sits in a draught, and the far side of the room lags. The better mount is the long wall, throwing down the length of the room. Use a corner only when no other structure will take the unit, and then ask for a capacity that can modulate and a vane aimed along the longer dimension. F-gas installation and Planning Portal checks on the outdoor unit are unchanged.
A short path from the fascia back into itself
Wall units want a clear throw of several metres so the air mixes before it is drawn back in. Tight into a corner, the supply travels a short path into the side wall or straight back into the fascia. The sensor is content. The opposite corner is not. People call that a weak unit. It is often a trapped unit.
The nearest chair on the first hot night
The nearest seat, bed or desk takes the draught because there is no distance for the jet to rise and diffuse. That complaint arrives on the first hot night. Expect a dead zone opposite a corner mount.
The long wall before anyone accepts the corner
Prefer the long wall, throwing down the length of the room.
- Prefer the long wall.
- Expect a dead zone opposite a corner mount.
- Do not oversize a unit that will short-cycle.
- Aim the vane along the longer wall if the corner is unavoidable.
A pier left between chimney, glass and wardrobes
Chimneys, glazing and wardrobes sometimes leave only a corner of solid wall. A smaller capacity that can run gently is kinder than the largest unit that fits the bracket. Ask the installer to set the vane along the longer dimension and to stand in the far corner and say honestly what that spot will feel like. A bigger unit usually short-cycles harder. The air still does not reach the far side.
A floor console moved a metre along the wall
A floor console in the corner has the same trap if the air cannot leave the corner. Moving the console a metre along a wall is often the whole repair. Say if furniture can move. Pointing the vane out of the corner helps in a small room. It does not turn a corner mount into a long throw. Ask the installer to show the direction before the bracket is fixed.
Wrong when the corner is chosen for a short pipe run
Installers like corners because the outdoor unit is the other side and the pipe run is short. A short pipe run on a bad throw is still a bad room. Pay for a longer insulated run to the long wall if that wall exists and the line can be trunked with the lids removable. Only use the corner for the pipes if the throw also works. The outdoor position still has to be lawful and quiet. In England, read the Planning Portal conditions. The company still needs F-gas certification. Neither is improved by tucking the indoor unit into a corner.
Core buying guides
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Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.