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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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  • Former Community Member
    0 Former Community Member

    AJJewsbury:




    I liked the 'specially labelled socket for a specific piece of equipment' in the 17th AM3 because it makes sense in scenarios like this, particularly for those who work from home with a home workshop or multiple pieces of IT equipment.



    But if the cluster of IT equipment was in danger of tripping a 30mA RCD in normal service then the leakage would have to be 15mA or above and then you're well into high protective conductor current territory and a BS 1363 socket is then verbotten.

     

    A debatable solution is to remove the upfront RCD and replace it with as many BS8277 30mA RCD protected socket outlets as are required to spread the leakage or identify the actual problem.



    Indeed debatable - as the 18th lists RCD types that are acceptable for additional protection - and BS 8277 isn't one of them. (Although there is a theory that that's just an oversight - I presume no-one's had any reassurance from the IET on that score yet?)


      - Andy.


    Good point on the high protective conductor currents - I'm sure a 60309 is out of the question in a living room though! Haha. ?


    I'm going to offer a test on his equipment to check how much earth leakage each device is producing. >15ma is excessive for properly operating domestic electronics, never mind being in the realm of high protective conductor currents.


    I agree, the lack of BS8277 is an oversight.

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  • Former Community Member
    0 Former Community Member

    AJJewsbury:




    I liked the 'specially labelled socket for a specific piece of equipment' in the 17th AM3 because it makes sense in scenarios like this, particularly for those who work from home with a home workshop or multiple pieces of IT equipment.



    But if the cluster of IT equipment was in danger of tripping a 30mA RCD in normal service then the leakage would have to be 15mA or above and then you're well into high protective conductor current territory and a BS 1363 socket is then verbotten.

     

    A debatable solution is to remove the upfront RCD and replace it with as many BS8277 30mA RCD protected socket outlets as are required to spread the leakage or identify the actual problem.



    Indeed debatable - as the 18th lists RCD types that are acceptable for additional protection - and BS 8277 isn't one of them. (Although there is a theory that that's just an oversight - I presume no-one's had any reassurance from the IET on that score yet?)


      - Andy.


    Good point on the high protective conductor currents - I'm sure a 60309 is out of the question in a living room though! Haha. ?


    I'm going to offer a test on his equipment to check how much earth leakage each device is producing. >15ma is excessive for properly operating domestic electronics, never mind being in the realm of high protective conductor currents.


    I agree, the lack of BS8277 is an oversight.

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