Like it or Not. The outdoor CU/DB is here to stay.

In the recent years there has been a massive increase in the use of outdoor switchgear for the domestic dwelling (PV, EV, Heat Pumps etc).  They are mainly metal but this then brings in the question of RCD protection for the enclosure itself and the characteristics of the supply cable to the CU/DB.


EG Is it OK for the CU to be fed from Henly Block (Other Brands are available) with only the protection offered by ( BS 1361 ) the main cut out fuse?  The standardized BS 1361 breaking capacity of these fuse-links is 33kA at 0.3p.f. However to cater for increasing fault levels all Lawson house service cut-out fuse-links have been ASTA tested to 80kA at 0.15 p.f.

A few suggestions

Height from floor and positioning.  IE can a child touch it, if so should the metal enclosure go inside a plastic or GRP enclosure?  GRP being preferred.

A breather plug/vent

A sticker on the front Stating.....All Penetrations to Enter from Below

A sticker on the front Stating.....IP rating, IK rating for the enclosure and Pollution Degree rating for the breakers inside if it is sold as a kit.

Pollution degree (IEC 60664-1)

Pollution degree    rough environment
1    In a clean environment or enclosed equipment
2    most common environment
3    Harsh environments such as factories
4    Outdoors where it is mainly exposed to the elements

As always please be polite and respectful in this purely academic debate.




Come on everybody let’s help inspire the future.

Parents Reply Children
  • And about the only thing sealed by that definition, is a potted joint, lids with O rings gaskets and so on do not hold against pressure unless piston sealed or clamped to a reference profile at close intervals, and all glands and screw heads need dowty washers which on electrical stuff they never have...

    In reality it always all leaks, slowly . And don't use stranded wire through compression glands and expect a seal either - air will pull along it between the strands once you get over a few inches water gauge of pressure, and thermal variations over a day/night in the UK for a truly closed  box in the sun can easily be a few hundred cm of water gauge  (a few PSI) between inside and outside.
    Mike

  • Then, I think that we agree that ordinary electrical gear is not sealed in the precise sense of the meaning.

    Even submarines are not necessarily as sealed as you might think. Water can collect in the bilges and be pumped out as with any other ship.

    I have a number of MK switches in my outbuildings at the bottom of (galvanized) conduit drops. All have a hole in the bottom corner, but they also all contain a few corpses of wee beasties.