RCD query

Discussion in 'Electricians' Talk' started by Johnupatree, Jul 5, 2021.

  1. MGW

    MGW Screwfix Select

    For a TN supply the RCD is "additional protection" so although desirable not required to ensure no protential danger, only with TT supplies is the RCD relied on for protection, so with a TN supply does not matter if RCD is type AC, A, F or B it is only "additional protection" with a TT supply however it does matter, so we have solar panels and EV charging which may require type B, and some applainces stipulate type A minium.

    However the question seems to be about type F, will a high frequancy AC cause a RCD to trip when it should hold in? DC is documented as causing RCD's not to trip, and so needs type B, but type F it seems are used so high frequancy will not cause eronious tripping.

    However since we don't know supply type, all when know is a type AC RCD is fitted, pointless debating if RCD is required, seems likely water ingress and some equipment needs to be repaired or replaced, only way to be sure which item is faulty is to test, and since I have an insulation tester I have never tried to work out how to test without one.
  2. Jim Kirk

    Jim Kirk New Member

    Unfortunately the 18Ed has become a minefield now with the addition of surge protection etc. You need a 20 odd way CU now between that and double RCD mainswitches in addition to the Non-RCD mainswitch.

    The last one I did before retiring was a 25 way job - I had to put it in the cupbaord next to the existing meter cupboard door after fitting a separate mainswitch and extending the tails. How do you explain that to the customer?

    RCBOs where required save space, identify faulty circuits and are no more expensive overall
    MGW likes this.
  3. MGW

    MGW Screwfix Select

    I would agree with @Jim Kirk I have a consumer unit however with a SPD, Main Switch, and 14 RCBO's fed from an isolator which is required so one can isolate else where when working in the consumer unit, so why is there an isolator in the consumer unit? It seems pointless, the supply goes from the DNO equipment to an isolator then to the CU and another isolator, the latter seems pointless.

    That does not seem to be the case with my unit, I only have two main switches which are in series so seems pointless, why does the CU have a main switch, it seems to have no use, to open cover HSE rules say isolate else where, so has to be an external main switch. Or pull the DNO fuse which is not permitted.

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