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Omitting 30ma RCD Protection for single S/O in a domestic property

Former Community Member
Former Community Member
I installed a dedicated circuit for a hifi system for a customer last year. The customer requested a 6mm2 radial from a 16A MCB housed in its own independent consumer unit into a single, un-switched socket outlet. No problem, bit unusual but no worries.I wired it using a 3c 6mm2 armoured cable as I half anticipated the forthcoming...


The hifi equipment is causing the rcd to trip when started up. I haven't been over to have a look but I am assuming that the startup current for the many power supplies (he has told me there are ten!) coupled with electronic earth leakage is causing a CPC current that is sufficient to trip the RCD (perhaps only 16ma but enough). The earthing is high integrity having a 6mm2 cpc + armour and the Zs is sufficiently low enough that the 16A MCB can be used for fault protection. So, if this wasn't domestic I'd ditch the RCD (or replace with a 100ma) assuming that my assumptions to this point are correct.


The customer has now decided he doesn't want RCD anyway for 'reasons' but I'm still wary of removing it in a domestic situation, not because I believe the installation would become less-safe but just because it contravenes regulations.


Assuming there's no fault on the equipment and it is just a case of startup/inrush current and earth leakage, what approach would you take? Remove the RCD and write it up as a deviation from 7671 with a signed disclaimer/waiver from the customer? Install a 100ma RCD? Do nothing and walk away? Something else?


Parents
  • 0
    The problem is that people have assumed BS 7288 SRCDs were suitable to comply with BS 7671, whereas BS 7671 has never stated they were ...


    Yet, it is clear from the SCOPE of BS 7288, that the


     

    I am sitting on my settee at home with a printed copy of the July/August 2019 Professional Electrician magazine that I picked up off the counter of the WED the electrical wholesaler I use.


    In the magazine is This article explaining how under floor electric heating can be installed.

    There is this quite clear and unambiguous statement by the NICEIC 





    Hang on, that advice is Industry Guidance, and should always have considered changes to the product standard.


    BS 7288:1990 did not have the same statements about limitations in terms of isolation, and requirements for the installation to already have Fault Protection and Additional Protection. Hence, before 2016, the advice was correct, but now, it's not the case.



    So we are in a position that some organisations' guidance needs to change - and BS 7671:2018 is wholly correct as things stand.
Reply
  • 0
    The problem is that people have assumed BS 7288 SRCDs were suitable to comply with BS 7671, whereas BS 7671 has never stated they were ...


    Yet, it is clear from the SCOPE of BS 7288, that the


     

    I am sitting on my settee at home with a printed copy of the July/August 2019 Professional Electrician magazine that I picked up off the counter of the WED the electrical wholesaler I use.


    In the magazine is This article explaining how under floor electric heating can be installed.

    There is this quite clear and unambiguous statement by the NICEIC 





    Hang on, that advice is Industry Guidance, and should always have considered changes to the product standard.


    BS 7288:1990 did not have the same statements about limitations in terms of isolation, and requirements for the installation to already have Fault Protection and Additional Protection. Hence, before 2016, the advice was correct, but now, it's not the case.



    So we are in a position that some organisations' guidance needs to change - and BS 7671:2018 is wholly correct as things stand.
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