A lightwell is a shaft, and an outdoor unit in a shaft often breathes its own exhaust. Hot air in cooling, and a restricted supply in heating, short-cycle the coil. Noise reflects off the opposite wall and into windows that face the same well. Service access fails when the only way in is a ladder through someone else's flat. Airflow and access fail more often than the wish to keep the unit unseen. Use the site only if the manual's clearances and a real service route both work. In England, Planning Portal conditions still apply.
Exhaust thrown at the opposite masonry
The fan throws air at a wall a short distance away. That air comes back warmer in cooling, or the coil cannot see enough fresh air in heating. The manual's front clearance is the test, measured to the opposite masonry, not to an open sky you cannot use. Seeing the unit is the smaller issue.
Windows on the well, drips, and a lease
A bigger fan speed does not fix a small well. If the gap is below the manual, the model does not go in that well. There is no universal metre rule that overrides the manual, and there is no special lightwell allowance. Opposite walls bounce air and noise. Manual clearances are measured to those walls.
Basement and ground-floor windows often open onto the same well. Defrost water and, if the drain is wrong, condensate, should not become a drip onto a cill below. Clear defrost water is normal in heating. An oil sheen is not. Talk to the freeholder before you treat a shared well as your plant room. The lease is the usual gate in a block. Planning and noise complaints are the other gate. Hidden plant can still be unlawful or leased to someone else.
Commissioning, coil cleaning and a failed fan all need a person and a panel. An F-gas company that cannot safely attend has not finished the design. Service access has to be real, not heroic. Pipe length and height difference back to the indoor unit are still manual limits, often in the familiar small-split classes, and always the figure for that outdoor unit.
Scaffold in the well, or a rise that is still too tall
If the only service route is scaffolding the well or crossing a neighbour's area, that cost and that permission belong on the price before the bracket is ordered. A short hop across a well can still be a tall rise against that outdoor unit's manual.
Frequently asked questions
Is a lightwell a good place because nobody sees the unit?
Seeing it is the smaller issue. Recirculation, reflected noise and poor service access are the usual reasons to refuse the well.
Can I point the fan upwards to clear the shaft?
Only if that orientation is allowed by the manual and the clearances still work. Many wells are simply too tight. The survey should say so.
Do planning rules apply if the unit is below street level?
Yes. Check Planning Portal heat pump conditions and the lease. Being out of sight does not remove either.
Who hears a unit at the bottom of the well?
Noise reflects off the opposite wall and into windows that face the same well. A unit that cannot be heard in your kitchen can be the only thing a lower flat hears. Noise complaints are a separate gate from how hidden the cabinet is.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
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.