10mm cable 10.5KW shower... What MCB? Crabtree...

Discussion in 'Electricians' Talk' started by alexjb1989, Jan 2, 2020.

  1. alexjb1989

    alexjb1989 Member

    Hi all,

    I know this has been discuss a lot, but I have a slightly different issue.

    I have a 10mm cable, so that is fine ( I am not entirely sure of the length to the consumer unit).

    We have just replaced our 8.5kw shower with a 10.5kw shower.

    The Triton manual says to use a 45MCB - However, we have a Crabtree Consumer unit and they do not have a 45MCB! Apparently it is something that has been discussed before...

    So... I have read that 40MCB would most likely be fine, as unless you sat under the shower for 45mins, its unlikely to overload. So I'm thinking to go with the 40MCB. They do a 50MCB, and a few are recommending that, but surely its safer to err on the side of caution with the 40MCB - worse case scenario, it trips a lot....


    Many thanks.
  2. Comlec

    Comlec Screwfix Select

    Fairly easy to work out

    load < MCB < cable capacity
  3. alexjb1989

    alexjb1989 Member

    ... Indeed
  4. Sparkielev

    Sparkielev Screwfix Select

    What crabtree is it ? Loadstar or starbreaker, you would be better off with a 50amp MCB
  5. Peterdevon

    Peterdevon Active Member

    If you go 50A the switch needs to be 50A as well. A 40A won't trip for 10,000 seconds at 45A
  6. alexjb1989

    alexjb1989 Member

    Thanks all for the help - It turns out I was told incorrectly, I only have a 6mm cable - so we went for the 8.5kw shower in the end.
    Cheers thoguh!
  7. peter palmer

    peter palmer Super Member

    Not necessarily, depends on what the load is, you could for example fit a 20A DP switch on a 32A Ring if its only switching a single socket.

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