1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

My Consumer Unit and RCD

Discussion in 'Electrics UK' started by mstizomad, 8 Apr 2018.

  1. mstizomad

    mstizomad

    Joined:
    19 Nov 2016
    Messages:
    88
    Thanks Received:
    0
    Country:
    United Kingdom
    Hello,

    The house that we have bought has a CU that was last tested in 2016.

    It has a 100A supply Main Switch and then a single 63A RCD that protects 7 x MCB:

    1 x 40A Shower - 10mm Cable
    1 x 32A Cooker - 6mm Cable
    1 x 32A Ground Floor Ring Main - 2.5mm Cable
    1 x 32A First Floor (small) + Kitchen Ring Main - 2.5mm Cable
    1 x 6A Ground Floor Lights Radial - 1.5mm Cable
    1 x 6A First Floor Lights Radial - 1.5mm Cable
    1 x 20A Outdoor Socket/Shed Radial - 2.5mm Cable

    Does this seem OK, or should i get a sparky to come and have a look and install an 80A RCD?

    Also, in a few months time, we will be completely removing the 40A shower circuit, as we will be switching to a Combi Mixer Shower. So that will obviosuly be less load on the system.

    Thanks
     
  2. Sponsored Links
  3. ban-all-sheds

    ban-all-sheds

    Joined:
    27 Aug 2003
    Messages:
    69,784
    Thanks Received:
    2,857
    Location:
    London
    Country:
    United Kingdom
    It's fine - when anybody adds up all of the ratings of their fuses/MCBs, they always come to more than the RCD rating, more than the main switch rating, more than the supply fuse rating.

    It's because you never have everything going flat out at the same time.

    http://www.tlc-direct.co.uk/Book/6.2.1.htm
     
    • Thanks Thanks x 1
  4. OwainDIYer

    OwainDIYer

    Joined:
    5 May 2010
    Messages:
    4,498
    Thanks Received:
    685
    Location:
    Stirlingshire
    Country:
    United Kingdom
    If there are 2 spare modules in the CU you'd be better getting the circuits split over 2 RCDs.

    Or at least shuffle the RCD along one and put the shed on iots own RCBO
     
    • Thanks Thanks x 1
  5. Brian shepherd

    Brian shepherd

    Joined:
    7 Mar 2018
    Messages:
    11
    Thanks Received:
    1
    Country:
    United Kingdom
    Diversity
     
    • Thanks Thanks x 1
  6. winston1

    winston1

    Joined:
    11 Jan 2010
    Messages:
    5,797
    Thanks Received:
    422
    Location:
    London
    Country:
    United Kingdom
    Someone wasted money using 1.5mm cable (note lower case c) for lights instead of 1.0mm, but it is not worth changing now.
     
  7. Taylortwocities

    Taylortwocities

    Joined:
    28 Jul 2006
    Messages:
    19,153
    Thanks Received:
    1,925
    Location:
    Oxfordshire
    Country:
    United Kingdom
    As above. The load is fine.
    What is wrong is having one RCD for everything.

    One simple fault on any circuit will kill every circuit in the house.

    Yes, get an electrician to advise if s second RCD can be installed and the board split to mean that you’ll only lose half of everything if there’s an earth fault.
    Or (better) have the MCBs changed for RCBOs.
     
    • Thanks Thanks x 1
  8. sparkwright

    sparkwright

    Joined:
    20 Aug 2009
    Messages:
    7,364
    Thanks Received:
    898
    Location:
    Dorset
    Country:
    United Kingdom
    If you go for all RCBOs, you would remove the 63A RCD.
     
    • Thanks Thanks x 1
  9. Sponsored Links
  10. sparkwright

    sparkwright

    Joined:
    20 Aug 2009
    Messages:
    7,364
    Thanks Received:
    898
    Location:
    Dorset
    Country:
    United Kingdom
    Sigh.

    What's this rubbish doing here?
     
    • Like Like x 1
  11. Taylortwocities

    Taylortwocities

    Joined:
    28 Jul 2006
    Messages:
    19,153
    Thanks Received:
    1,925
    Location:
    Oxfordshire
    Country:
    United Kingdom
  12. mstizomad

    mstizomad

    Joined:
    19 Nov 2016
    Messages:
    88
    Thanks Received:
    0
    Country:
    United Kingdom
    Hi, ok thanks. What is the main advantage of RCBOs? Is each like a combined RCD and MCB for each individual circuit?
     
  13. EFLImpudence

    EFLImpudence

    Joined:
    7 Jul 2010
    Messages:
    32,198
    Thanks Received:
    3,492
    Location:
    Retired to:
    Country:
    Portugal
    Yes.
     
    • Thanks Thanks x 1
  14. Taylortwocities

    Taylortwocities

    Joined:
    28 Jul 2006
    Messages:
    19,153
    Thanks Received:
    1,925
    Location:
    Oxfordshire
    Country:
    United Kingdom
    Exactly.

    As i said in my earlier post, if you have one RCD at the origin, you lose everything if there is one earth fault.
    With a split-load board (eg two RCDs) you lose half of everything if there is an earth fault.

    With RCBOs, you only lose the circuit where the fault is. That is a much better segmentation of circuits, but more expensive as MCBs average about £5 each, RCBOs can be between £25-£40 depending on the make and supplier.
     
    • Thanks Thanks x 1
  15. ban-all-sheds

    ban-all-sheds

    Joined:
    27 Aug 2003
    Messages:
    69,784
    Thanks Received:
    2,857
    Location:
    London
    Country:
    United Kingdom
    Ask the Mods - they are the ones who want it here.
     
  16. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Sponsored Links
Loading...

Share This Page