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High protective conductor currents - Deletion of 543.7.1.204

AJJewsbury

543.7.1.204 - the one about duplicate c.p.c.s needing to be 'terminated independently of each other' - has gone.

Does anyone understand the thinking behind this? It seems a bit odd to me.

Given that (in my experience) more problems occur at terminals rather than along cable runs, if we need the c.p.c.s to be duplicated, it seems like a bit of a flaw that one single loose connection can make them both useless simultaneously. I can see that in some instances (e.g. a terminal on a socket on a ring) that losing a single terminal carries a limited immediate risk (as the leakage current from a single socket should be small and all other sockets are still connected to a c.p.c.) but in other instances - say the connection of both c.p.c.s to the earth bar in a DB - that single fault could be very significant.

   - Andy.

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  • If we are talking about socket-outlets, Regulation 411.3.3's development through 17th and 18th Editions has effectively removed the necessity for this. Socket-outlets up to 32 A are now required to have 30 mA RCD protection

    But 30mA RCD protection is only needed for sockets, not necessarily the entire socket circuit - and now we have BS 7288 RCD sockets back - it's quite easy to imagine >>10mA protective conductor currents on a 32A circuit.  I can think of plenty of office environments originally wired with a ring covering a significant number of desks with wiring in dado trunking (so no RCD requirement for cables concealed in walls) where RCD sockets would be a very obvious choice.

    I dare say some commercial lighting circuits will likely fall into this category too as we switch to electronic ballasts with their filtering capacitors and subsequent earth leakage.

    Even if 543.7 doesn't apply as often, that doesn't seem to justify watering down its provisions for the remaining situations where it does still apply.

    Well, not quite yet Geoff. We still have accessories with not one but TWO terminals for CPCs, which i believe we wouldn't have if it wasn't for your suggestion. Thank you.

    +1 for that. In fact the twin terminals have proved very useful on several occasions where I've ended up with 3off or 4off 4mm² c.p.c.s to terminate - for some reason BS 1363's terminal capacity thinking seems to overlook that you often want a fly lead to the back box in addition to the two ring (or radial in and out) and one spur conductors.

       - Andy.

  • in reply to AJJewsbury
    AJJewsbury said:
    +1 for that. In fact the twin terminals have proved very useful on several occasions where I've ended up with 3off or 4off 4mm² c.p.c.s to terminate - for some reason BS 1363's terminal capacity thinking seems to overlook that you often want a fly lead to the back box in addition to the two ring (or radial in and out) and one spur conductors.

    Agreed.

    However, still don't see many BS EN 60309-2 outlets with two PE terminals.

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  • in reply to AJJewsbury
    AJJewsbury said:
    +1 for that. In fact the twin terminals have proved very useful on several occasions where I've ended up with 3off or 4off 4mm² c.p.c.s to terminate - for some reason BS 1363's terminal capacity thinking seems to overlook that you often want a fly lead to the back box in addition to the two ring (or radial in and out) and one spur conductors.

    Agreed.

    However, still don't see many BS EN 60309-2 outlets with two PE terminals.

Children
  • in reply to gkenyon

    No but they do have two screws, so effectively two connections to the CPC. The real faults are loose screws not broken conductors.

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