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

Sergio Fernandez

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

  • Sinking ball valve floats in hot water header tanks.

    If there is a pinhole in the float below water level, as the water in the cylinder is heated, the hot water expands and goes up into the header tank warming the water in the header tank and the float, the air in the float expands when it warms up and bubbles out of the pinhole, as the air in the float cools it sucks water back and the float fills with water up to the level of the pinhole and it may no longer have enough buoyancy to shut the water valve off.

    The same heating and cooling process that results in IP rated outdoor electrical fittings filling with water.

  • in reply to Sparkingchip

    Exactly that  ! the daily 'breathing' of air in and out with temperature will occur, short of building the enclosure with seals like a submarine,  so the trick  has to be to make sure the intake is not somewhere that rain water or condensation will collect, by providing one you have control of to neutralise the pressure gradient, rather than uncontrolled blow-by into cable glands and fixing screws.
    I must admit, these photos remind me of why steel boxes outdoors are really not a good idea, fire containment or not, a decade is a long time for powder coated mild steel to survive the elements in the UK  There are situations where there  is a lot to be said for a suitable plastic, reinforced with glass fibres for larger volumes and that is before we get onto the exported PME earths and all the rest of it.

    regards Mike.

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  • in reply to Sparkingchip

    Exactly that  ! the daily 'breathing' of air in and out with temperature will occur, short of building the enclosure with seals like a submarine,  so the trick  has to be to make sure the intake is not somewhere that rain water or condensation will collect, by providing one you have control of to neutralise the pressure gradient, rather than uncontrolled blow-by into cable glands and fixing screws.
    I must admit, these photos remind me of why steel boxes outdoors are really not a good idea, fire containment or not, a decade is a long time for powder coated mild steel to survive the elements in the UK  There are situations where there  is a lot to be said for a suitable plastic, reinforced with glass fibres for larger volumes and that is before we get onto the exported PME earths and all the rest of it.

    regards Mike.

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