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Struggling with insulated consumer units and information on power dissipation

Alan B

I am quoting for a new consumer unit to go in to  a domestic garage. Supplies 3 circuits in the garage and a couple of circuits to other outbuildings.

Especially with the recent guidance on metallic consumer units outside I have been leaning towards using a plastic consumer unit, then comes the challenge.

I don't think anyone still builds populated consumer units for more than 4 ways. So then I look at building my own and power dissipation, very little information available from what I can see, the only company providing data is MCG at 1a very low 11W.

The best I can find is that some enclosures state then are ok for say 63A, no idea what the assumed heat dissipation is. Also heat a dead end when looking for heat dissipation from RCBO's, I remember in the past seeing 12 to 15w at full load. So I seam to be left with a choice of putting a metal board in and hope it doesn't suffer from condensation, or puta plastic one in and hope it doesn't over heat. I could also put a metal board in a plastic enclosure, a bit less risk with heat.

I could probably just use any plastic din rail enclosure and not have an issues, but frustrating this is so difficult.

Thoughts?

  • 0 in reply to tattyinengland

    lThose Blakley units are really very good & solid, and optionally available in stainless steel as well as with rain covers on request. (https://www.blakley.co.uk/products/permanent-distribution/ip66-mcb-distribution-boards/distribution-boards-ip66-125a-spn/14w-125a-ip66-spn-mcb-distribution-board/)

    However most steel CUs are not full seam welded, phosphated and epoxy coated like that. A light dusting of powder coat is more likely, so  do not expect the same life from a wylex.

    for temporary outdoor power, personally I find rubberbox very good, but not a cheap option either ;-)
    Mike.

  • 0 in reply to Gary Jones

    BS 7671 does not say you must use a metal CU in an outbuilding or garage - it says just lists it as one possible fire reduction measure for installations within domestic buildings. I agree that the practical effect is that mostly folk fit steel everywhere willy nilly, and that is what most wholesalers stock - but there are plenty of places where the environment makes that unwise. its not that many decades ago we were ripping out badly corroded metal switchgear where the earthing had rotted off in church basements and farmyard out-buildings to replace it with the then more modern  non-rusting plastic alternative. A lot of the problem is the choice of which plastics, and if suitable fire retardant has been added.  In many ways, CU makers have been quite sloppy. After all, meters and service heads are nearly all insulating by design these days, and in many DNO regions if you report a cast iron service head, they will come and change it (very carefully if there is an asbestos risk) for a new one.

    I can't see the detail of the original posters situation of course, but the world is not as simple as 'steel good - plastic bad' in all cases.
    Mike.

  • 0 in reply to Colin Jenkins

    I agree much better to stick with what BS7671 states and use metal CU. The product below would be ideal and will not rust. 

    FuseBox F100GRA Garage Consumer Unit - The FuseBox F100GRA Garage Consumer Unit is a popular choice for residential garages due to its durability, compact design, and excellent safety features.

    Key features of this consumer unit include:

    • Design - The FuseBox F100GRA is a metal consumer unit constructed from high-quality steel, ensuring durability and protection against impact and environmental conditions. It is designed to accommodate various electrical circuits with up to ten usable ways, providing flexibility for connecting multiple devices and appliances.
  • 0

    Well, I do a few site temporaries for construction sites outdoor compounds.

    I usually source my DBs from a company called Blakley

    These things sit out in the cold & rain and snow for years. They're pretty tough. Perhaps see if they do a DB you'd be happy with?

  • 0 in reply to Chris Pearson

    it is fixed infrastructure. I'd like the wiring and accessories to last the life of the building, much like the bricks and roof tiles which are also cheap, a brick is cheaper than a CU (!)  if it's that sort of garage and not some temporary wooden thing.
    I see no reason why PVC or PE wires going in now that are lightly loaded and out of the sunshine, should not be still in service in a century or two. A washing machine is not infrastructure, and has parts that perish or fatigue over time and so has finite life, looking at our own washing machine history, typically ten to twenty years perhaps.  Cars seem to fail due to something being beyond economic repair, suspension, dual mass flywheels etc. or collision damage.  Corrosion in a big way was more of a 20th century thing  - I presume modern paints are better, and maybe modern steels too.

    Mike.

  • 0 in reply to gkenyon
    gkenyon said:
    CU vs the vehicle (latter may be better protected against salt corrosion than damp)

    I find it extraordinary that cars made in the past 15 years or so do not rust.

    mapj1 said:
    a car gets driven about and maybe replaced after a few years, a CU less so

    Strange that people seem to want something as cheap as a CU to last longer than a car!

    How long do people expect a washing machine, for example, to last?

  • 0 in reply to Chris Pearson

    If the garage is so damp that a steel-enclosed DB would rust away, it will not do much for the cars.

    At lot depends on individual circumstances - how much rain seeks under the up-and-over door when it rains with the wind in the wrong direction, how much overhanging trees reduce warming/drying when they sun's out. Even within the garage a metallic box screwed directly to a single brick outside wall is likely to get cooler quicker (and so suffer more from condensation) than a metal box stood off the floor on rubber tyres and with a foot or so of still air around it. Of course in the old days we'd mount CUs on a slab of chipboard with a 3/4" air gap behind it which would act as a thermal break, but that's probably not fashionable now. It's not just the steel enclosure rusting either - a bit of damp can wreck havoc to the terminals and internals of delicate modern devices like RCBOs.

       - Andy.

  • 0

    Hello Alan.

    Fit a metal one. The metal 8-way Wylex all RCBO CU  in my unheated detached garage has been there since 2008 and has no corrosion at all.

  • 0 in reply to Chris Pearson

    a car gets driven about and maybe replaced after a few years, a CU less so - what about a CU in a car port for example ?

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    If the garage is so damp that a steel-enclosed DB would rust away, it will not do much for the cars.

    Yes ... and no ... it depends on how long you want to keep the cars, but also on whether there's anything else going on (such as salt spray in the atmosphere) that might affect the corrosion of the CU vs the vehicle (latter may be better protected against salt corrosion than damp).

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