Outside Light Install in NR15

Outdoor lighting fails in predictable ways. Water gets into a fitting that was never rated for the position it was put in, and fixings corrode until the thing hangs off the wall.

Selection comes first. IP44 covers a sheltered porch. Exposed wall lights and floodlights want IP65, and anything ground-recessed or near water wants more. On the Norfolk and Suffolk coast salt-laden air attacks fixings, gaskets and thin aluminium housings, so cheap fittings fail years earlier a mile from the sea than they do inland.

Cable route comes second. A run underground has to be steel wire armoured, with the armour earthed and used as the protective conductor. IET Guidance Note 1 recommends burying it at least 500mm deep, with marker tape or cable covers over the route. Twin-and-earth pushed through a length of hosepipe is not a garden cable.

Then earthing. On a PME supply, BS 7671 restricts exporting the earth to outdoor metalwork and outbuildings, because a broken PEN conductor can leave a metal lamp post or garage frame at a dangerous voltage relative to true earth. The answer is a local earth electrode and RCD protection for the outdoor part.