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30mA RCDs for sockets - AMD2

AJJewsbury
As you many (or may not) have noticed, AMD2 deletes the option to omit 30mA RCD protection for socket outlets (by documented risk assessment). So then ALL sockets rated ≤32A will need to be on a 30mA RCD.


This strikes me as unhelpful for some situations - e.g. feeds to server racks in data centres where the cumulative protective conductor currents will likely nuisance trip a 30mA device and hard-wiring instead using plugs & sockets is undesirable as non-skilled persons (electrically) are likely to need to be able to disconnect/reconnect the supplies to racks (sometimes under 'duress' conditions).


There are probably other situations too - I've seen 16A sockets used to feed lights high up in major railway station canopies (presumably so the fittings can be readily disconnected and brought to ground level for maintenance) - where I guess the risk of loss of lighting far outweighs the risk from shock.


OK we possibly get around the letter of the regs by hard-wiring to a short length of flex and having a connector (trailing socket) on the end of that (thus side-stepping the definition of a socket outlet which has to be connected to fixed wiring) - but that hardly seems to be in the spirit of the regs, nor necessarily a good technical solution where a fixed socket would have been the better solution.


Further thoughts?


  - Andy.
  • 0
    One may always think of exceptions, such as access limited to skilled persons, but it seems eminently sensible to me.


    Problem is the eye-wateringly high cost of three-phase RCBOs - they make AFDDs look cheap!
  • Former Community Member
    0 Former Community Member
    AJJewsbury:

    Further thoughts?


    I think the trajectory has been heading along these lines and Amd 2 finally implements the blanket requirement, Andy - regardless of circumstances.


    Like you, I'll be busy dreaming up the work arounds for those situations where RCD's are not appropriate, nor offer any real safety benefits


    That might include 63A socket outlets, where 32A would have sufficed (and the MCB may well still be 32A) and the interposition of all manner of gizmo's to ensure those socket outlets are not connected to fixed wiring - plus the increasing use of "non socket" socket outlets - ie use an alternative means of cable coupler device


    I think we lost the plot when we disregarded the "skilled and instructed" in favour of "carelessness of users"


    Regards


    OMS


  • 0
    I think that this is as OMS says, simply completing a job started many years ago. Whether it is technically feasible is more interesting. It will mean those larger appliances which have high inrush current will either have oversize sockets or be wired in directly.  This is probably not a good solution as the CPD will either be undersized for the socket or the flexible cable undersized for the CPD. Neither of these is a serious problem, but somewhat undesirable. My compressor tends to trip the circuit RCD occasionally due to inrush current, I put up with it as I do not want it permanently wired, the socket is also used for other things. I could fit more wiring but it is just too much trouble. The best choice, do nothing!
  • 0
    Or in the case of the compressor, perhaps an inrush limiter.

    The bigger problem I see is racks of radio or IT equipment with EMC filters.

    I fear it may encourage folk to try and reduce the amount of filtering, which with my EMC hat on is a very bad thing, already the standards are nothing like  tight enough to allow co-location of kit that only just pass the immunity specs along side things that only just meet the emissions spec - things work because good designs have 10-20dB of margin between the minimum spec and the performance (or are not co-located).

    If we did not have to consider L-N reversal in product design, then one could have larger capacitors L-N and N-E and omit the one wired L-E, but given the European influence I do not see that.

    If we had 3 phase appliances at lower currents, then the leakage from 3 identical filters each leaking from one phase L-E does more or less cancel, but 3 phase 16A connectors is not the UK way, and a supply suitable for that not always available anyway.

      I'd prefer and predict a lot of 63 A connectors with 2.5mm cables and similar cunning, as folk are not keen to put 'does not meet BS7671 by design' in the paperwork.

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