Can anyone suggest a straight swap for this MCB?

Discussion in 'Electricians' Talk' started by Carld, Mar 24, 2023.

  1. Carld

    Carld Member

    Hi

    I've had the boiler removed and have a spare MCB, have a 10.5kw shower I'd like to put in its place. Any idea which MCB would be a straight swap?

    Cheers

    T
     

    Attached Files:

  2. FlyByNight

    FlyByNight Screwfix Select

    NONE
     
    Ind spark likes this.
  3. baldelectrician.com

    baldelectrician.com Well-Known Member

    You need a new consumer unit

    If you look at the shower instruction manual it will state a 30mA RCD, you have a 100mA RCD in the picture
    Also the RCD is an AC type RCD, these are no longer recommended for most circuits (Amendment 2 BS7671), as the RCD does the rest of the house there may be an issue with DC issues on other circuits.

    See RCD info I add on EICR's below
    Older AC type RCD's are prone to being blinded by dc leakage from other items plugged in to the property. In other words this RCD may fail to operate when other electronic items are plugged in which leak DC in to the mains.
    Regulation 531.3. 3 of BS 7671:2018+A2:2022 states that the appropriate RCD shall be selected according to the presence of DC components and AC frequencies. Further, Type AC RCDs shall only be used to serve fixed equipment, where it is known that the load current contains no DC components.
     
  4. Jimbo

    Jimbo Screwfix Select

    Do you think it worthwhile to swap existing ACs for As?
     
  5. The Happy Builder

    The Happy Builder Screwfix Select

    You might get a MCB through EBay for around fifty quid, if someone just happens to have put one up for sale.

    In all honesty, you will be better off putting your fifty quid towards having the consumer unit replaced, because as @baldelectrician.com pointed out you need a lower rated RCD as well.
     
  6. Carld

    Carld Member

    Many thanks fellas.

    T
     
  7. FlyByNight

    FlyByNight Screwfix Select

    @Carid As above, £50 for an extra MCB (not guaranteed fully functional), £50-80 for an RCCB (not guaranteed fully functional), £100 labour ...

    A new 4 circuit CU, with expansion room plus changeover will not be much more!
     
  8. baldelectrician.com

    baldelectrician.com Well-Known Member

    We do EICR's
    I always now recommend repalcement on an EICR for existing RCD's that are type A. It's really a cover my back thing as it's better to be save than sorry

    With the abundance of electronic things in properties now I don't know if an exisitng type AC RCD will be affected adversely but I do recommend chaging to clients- it is up to the client if they accept or ignore my advice but the buck is passed to them in the instance they decide not to.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice