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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?


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    mapj1:

    Indeed, and even if they do not meet the letter of the current standard as written, an RCD socket or spur is a good way of performing a cost-effective addition of a stair lift or whatever, such that the new bit is protected to a  level equivalent to current standards, while the rest is no more dangerous than it was the day before.

     




    But BS 7288:2016 itself says it's not an RCD equivalent to a BS EN 61008 or BS EN 61009 RCD ... so without further clarification on the specific points we've been discussing re BS 7671,  I'm not sure "the new but is protected to a level equivalent to current standards" - however, the former BS 7288:1990 could perhaps demonstrate it was?

     



    One of the unintended consequences of regulation changes and restriction as to what is permitted, pushes up costs and in turn that does mean that the old stuff we were trying to get rid of tends to stay in service longer .

    I fear that those informing the committees, live in million pound houses in the South East, all have TNC-s  or TNS supplies, and think nothing of a few hundred quid here or there. Reality  is that further from the centre, there is TT, there are fused neutrals, and 50 year old wiring is very much still in service on BS3036 fuses, and a CU change is an expensive luxury that may have to wait it's turn.



    Installations to previous versions of BS 7671 and the Wiring Regulations are not necessarily deemed unsafe, at least according to BS 7671 itself.


    However, it's also true industry, and standards, shouldn't stand still.


    Certainly in the case of BS 7288, there must be a reason why it says what it does ... and I'm not going to argue one way or the other on that without being in possession of the facts.

     

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  • 0

    mapj1:

    Indeed, and even if they do not meet the letter of the current standard as written, an RCD socket or spur is a good way of performing a cost-effective addition of a stair lift or whatever, such that the new bit is protected to a  level equivalent to current standards, while the rest is no more dangerous than it was the day before.

     




    But BS 7288:2016 itself says it's not an RCD equivalent to a BS EN 61008 or BS EN 61009 RCD ... so without further clarification on the specific points we've been discussing re BS 7671,  I'm not sure "the new but is protected to a level equivalent to current standards" - however, the former BS 7288:1990 could perhaps demonstrate it was?

     



    One of the unintended consequences of regulation changes and restriction as to what is permitted, pushes up costs and in turn that does mean that the old stuff we were trying to get rid of tends to stay in service longer .

    I fear that those informing the committees, live in million pound houses in the South East, all have TNC-s  or TNS supplies, and think nothing of a few hundred quid here or there. Reality  is that further from the centre, there is TT, there are fused neutrals, and 50 year old wiring is very much still in service on BS3036 fuses, and a CU change is an expensive luxury that may have to wait it's turn.



    Installations to previous versions of BS 7671 and the Wiring Regulations are not necessarily deemed unsafe, at least according to BS 7671 itself.


    However, it's also true industry, and standards, shouldn't stand still.


    Certainly in the case of BS 7288, there must be a reason why it says what it does ... and I'm not going to argue one way or the other on that without being in possession of the facts.

     

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