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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.

Parents

  • If a terminal is subject to failure, surely that's the case regardless of the size of cpc connecting to it?

    My feeling is that a given terminal may well be less reliable when holding a smaller conductor than a lagrer ones - some of us tend to double over smaller conductors to try and fill the terminal, but that practice doesn't seem to be universal. I'm sure there's a greater fear of overtightnening and damaging smaller conductors, so perhaps a natural tendency for screws not to be quite so tight, and less 'give' in the smaller conductors in any event. I'm sure we've all dropped off a socket front to find the wires popping out of the terminals - perhaps solid rather than stranded nature of the smaller sizes (in T&E) can result in more stress on the connections that makes a contribution too.

        - Andy.

  • in reply to AJJewsbury
    AJJewsbury said:
    My feeling is that a given terminal may well be less reliable when holding a smaller conductor than a lagrer ones - some of us tend to double over smaller conductors to try and fill the terminal, but that practice doesn't seem to be universal.

    Is there evidence for this? Are we seeing regular problems attributed to this?

    AJJewsbury said:
    m sure there's a greater fear of overtightnening and damaging smaller conductors, so perhaps a natural tendency for screws not to be quite so tight, and less 'give' in the smaller conductors in any event.

    Torque settings and manufacturer's instructions?

    AJJewsbury said:
    I'm sure we've all dropped off a socket front to find the wires popping out of the terminals - perhaps solid rather than stranded nature of the smaller sizes (in T&E) can result in more stress on the connections that makes a contribution too

    Perhaps ... but that could be resolved by requiring stranded (min 7 strands) for conductors used in such circuits as an equally valid installation option?

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  • in reply to AJJewsbury
    AJJewsbury said:
    My feeling is that a given terminal may well be less reliable when holding a smaller conductor than a lagrer ones - some of us tend to double over smaller conductors to try and fill the terminal, but that practice doesn't seem to be universal.

    Is there evidence for this? Are we seeing regular problems attributed to this?

    AJJewsbury said:
    m sure there's a greater fear of overtightnening and damaging smaller conductors, so perhaps a natural tendency for screws not to be quite so tight, and less 'give' in the smaller conductors in any event.

    Torque settings and manufacturer's instructions?

    AJJewsbury said:
    I'm sure we've all dropped off a socket front to find the wires popping out of the terminals - perhaps solid rather than stranded nature of the smaller sizes (in T&E) can result in more stress on the connections that makes a contribution too

    Perhaps ... but that could be resolved by requiring stranded (min 7 strands) for conductors used in such circuits as an equally valid installation option?

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