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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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    Okay, we are seriously in a situation where the left hand doesn’t know what the right hand is doing and it really is time that the IET should have issued clarification on the intentions of the Wiring Regulations committee regarding the use of BS8277 RCD protected socket outlets and connection units.


    THERE IS ABSOLUTELY NO DENYING that the NICEIC officially promotes the use of BS8277 RCD connection units as an acceptable means of providing RCD protection.


    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 


    Typically, in older installations fuses to BS 3036 or circuit breakers to BS 3871 maybe found. Where this is the case and it is not practical to include RCD protection at the consumer unit a 13 A RCD spur maybe installed locally from an existing circuit as shown in Fig 2. 


    Someone at the IET needs to get their act together and resolve the potential issues of using BS8277 equipment.


    Andy Betteridge 

Reply
  • 0
    Okay, we are seriously in a situation where the left hand doesn’t know what the right hand is doing and it really is time that the IET should have issued clarification on the intentions of the Wiring Regulations committee regarding the use of BS8277 RCD protected socket outlets and connection units.


    THERE IS ABSOLUTELY NO DENYING that the NICEIC officially promotes the use of BS8277 RCD connection units as an acceptable means of providing RCD protection.


    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 


    Typically, in older installations fuses to BS 3036 or circuit breakers to BS 3871 maybe found. Where this is the case and it is not practical to include RCD protection at the consumer unit a 13 A RCD spur maybe installed locally from an existing circuit as shown in Fig 2. 


    Someone at the IET needs to get their act together and resolve the potential issues of using BS8277 equipment.


    Andy Betteridge 

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