RCD as main switch

Discussion in 'Electricians' Talk' started by peter palmer, Jul 10, 2016.

  1. peter palmer

    peter palmer Super Member

    A property I recently went to to install a few new lights has a TT supply, there are 2 mains units, both remote from the meter. One had normal tails under the floor and the other had a piece of SWA supplying it. It had a 30ma non-time delayed RCD as the main switch.

    Now apart from having the wrong type of RCD to cover the tails etc (should be an "S" type) whats the score with using a 2 pole RCD as an isolator switch? I would prefer a normal isolator first.
  2. philthespark

    philthespark Active Member

    was there an s type rcd by the meter?
  3. peter palmer

    peter palmer Super Member

    No, this RCD was at DB1 position, it went from the meter into a SWA under the floor to DB1 position, through this RCD and then split via a couple of henleys into normal tails, one set went into DB1 and the other set went under the floor to DB2 position.
  4. Comlec

    Comlec Screwfix Select

    Peter, I have seen this too. Looked it up in the regs (Table 53.4) - looks like a correctly rated 2 pole RCD (BS EN 60947-2, BS EN 61008-1 or BS EN 61008-1) can be used as an isolator.

    I would prefer and Isolator then RCD, making it easier to replace a failed RCD. An event more likely than a failed main isolator..
  5. philthespark

    philthespark Active Member

    I've seen this before and tbh would agree with you,I'm more concerned about the lack of a time delayed rcd next to the meter though.
  6. nffc

    nffc Active Member

    Would a time delay RCD provide suitable protection to non-armoured tails installed under the floor?
  7. spinlondon

    spinlondon Screwfix Select

  8. spinlondon

    spinlondon Screwfix Select

    Problem with this set up is combined earth leakage can cause the 30mA RCD to trip.
    Yes it complies with the Regs, if you ignore the inconvenience that would be caused by a fault on one circuit affecting all circuits.
    I would prefer an up front 100mA RCD, with RCBOs where necessary
    philthespark likes this.

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