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.

  • May I add that upon inquiry, it was found that none of the usual wholesalers were familiar with or had stocked this particular plug.

  • In my engineering judjement if you drill the top of the enclosure moisture will always get in.  It also lacks a breather vent/drain. 

    If the enclosure is sealed, it does not need a drain. However, I accept that moisture might track inside a conduit.

    If you attach a cable or conduit to the top of an enclosure which is exposed to the elements, are you not duty-bound to ensure that it is water-tight?

  • Perhaps order in from  a more specialized  wholesaler - electrical and electronic places do them, but I agree screwfix B& Q etc don't.

    Electrics

    https://www.tlc-direct.co.uk/Products/WK20VP.html?

    https://www.tlc-direct.co.uk/Products/WK20VPG.html?

    https://www.cef.co.uk/catalogue/products/1865506-m12-sealed-16l-h-anti-condensation-valve-ip68?

    Electronics.

    https://uk.farnell.com/schneider-electric/nsycag12lph1/valve-anti-condensation-16l-h/dp/2499479?

    https://www.mouser.co.uk/ProductDetail/Amphenol-LTW/VENT-PS1NBK-O8001?

    https://cpc.farnell.com/hylec/jdae12pa7035/venting-plug-ip66-ip69k-grey-m12/dp/EN83189?

    hope that helps

    PJ

  • Vent plugs a little too late for these;

  • 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.

  • 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.

  • If the enclosure is sealed, it does not need a drain. However, I accept that moisture might track inside a conduit.

    Not true. Moisture is always in the air that's sealed in a gas-tight enclosure, which can condense if the temperature changes quickly outside the enclosure. In addition, there are ways that moisture can enter in vapour/gaseous form in enclosures that are only sealed against water but not gas.

  • If the enclosure is sealed, it does not need a drain

    I disagree with this.

    If the enclosure is outside in the UK then moisture will form internally due to the warming and cooling cycles.  When the air inside the enclosure hits the Due Point then it will condensate on the inside of the enclosure.

  • The other thing to consider is that under fault conditions the Normal user may need to reset the device. 

    That is the same indoors.

    I would like to think that indoors there would be no water or moisture in the the CD/DB.  Outside it is highly probable that there will be water or moisture present in the CU,  this could possibly cause damage to the Circuit Protective Devices causing them not to function properly or deliver electricution or shock when touched.

  • I would like to think that indoors there would be no water or moisture in the the CD/DB.  Outside it is highly probable that there will be water or moisture present in the CU,  this could possibly cause damage to the Circuit Protective Devices causing them not to function properly or deliver electricution or shock when touched.

    On the other hand we've been putting MCBs, RCBOs etc in outdoor boxes for decades in things like caravan hookup (and similar for boats) ... and no great disasters seem to have happened.

       - Andy.