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

TT system and RCBO's

Discussion in 'Electrics UK' started by STI, 18 Oct 2011.

  1. STI

    STI

    Joined:
    5 Aug 2009
    Messages:
    426
    Thanks Received:
    27
    Location:
    Birmingham
    Country:
    United Kingdom
    Im trying to get my head around the CU requirements for a TT system. If i was to fit a CU with RCBO's protecting all the circuits, would the main CU switch 100A or 63A need to be a time delayed RCD or could it just be a straight forward isolator switch as the RCD protection is provided by the individual circuits RCBO's.
    The current set up is 3036 rewirables with a voltage operated earth leakage type D isolator switch between the main fuse and the CU.
    So would i need an RCD isolator between the main and the CU then a main switch in the CU which is a time delayed RCD then to individual circuit RCBO's.

    Seems an awful lot of RCD type protection and i still have a single failure point in two places.

    I am aware this is all notifiable but i am at my planning stage.
     
  2. Sponsored Links
  3. echoes

    echoes

    Joined:
    27 Mar 2007
    Messages:
    1,246
    Thanks Received:
    142
    Location:
    Surrey
    Country:
    United Kingdom
    If all circuits are on 30mA RCBO's, no further RCD protection is needed. The main switch provides double-pole isolation. See p. 16 OSG, Fig 2.3

    Futher consideration needed if you wish to be able isolate part of the installation.
     
    • Thanks Thanks x 1
  4. JohnW2

    JohnW2

    Joined:
    28 Jan 2011
    Messages:
    48,603
    Thanks Received:
    3,189
    Location:
    Buckinghamshire
    Country:
    United Kingdom
    Indeed. In fact, as recently discussed here, not only is further RCD protection not required in that situation, but it is also undesirable ... a N-E fault tripping any of the (assumed single-pole) RCBOs would probably also take out an up-front RCD (even if time delayed), thereby taking out the whole installation and defeating the point of having separate protection for each final circuit.

    Kind Regards, John
     
    • Thanks Thanks x 1
  5. 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

     
Loading...

Share This Page