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543.6.1 the protective conductor shall be incorporated in the same wiring system as live conductors (re: overcurrent protection)

psychicwarrior

Hello good day to all

In an *all* PVC trunk/conduit wiring system (using insulated single conductors), what is the implication of 543.6.1 ?

- does it mean that a protective conductor (shared or per circuit) has to be in *each* part of the wiring system that a live conductor runs or close by ?

e.g. one cannot send feed and switched live on their own down to a switch with a cpc coming to the switch from elsewhere

If yes or no, what is the safety issue intended to be addressed with this one ?

It feels like I am misinterpreting this.

Cheers

Habs

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    does it mean that a protective conductor (shared or per circuit) has to be in *each* part of the wiring system that a live conductor runs or close by ?

    Only in certain contexts - so not in a TT system (or other situations where fault protection is by something other than an overcurrent device), nor where no c.p.c. is required (e.g. a system fully under section 412). [I'm presuming that in this context 'fault protection' is referring to section 411 rather than 434 - I don't think the wording is particularly clear]

    But back to the point... I might also add in 521.8.1 - conductors of a circuit not to be distributed over different cables/conduits etc. So in that context what 543.6.1 seems to be saying to me is: where earth fault currents are high then route the c.p.c. in the same way as a live conductor. You might also think of 521.5.1 that requires all conductors (incl. c.p.c.) to go through the same hole in ferrous enclosures etc.

    To me it all feels to be about the interaction of high fault currents - trying to keep the 'flow' and 'return' conductors close together so they cancel out as much as possible - and avoiding large separation of conductors that can cause lots of magnetic problems - from interference to increased loop impedances.

       - Andy.

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    does it mean that a protective conductor (shared or per circuit) has to be in *each* part of the wiring system that a live conductor runs or close by ?

    Only in certain contexts - so not in a TT system (or other situations where fault protection is by something other than an overcurrent device), nor where no c.p.c. is required (e.g. a system fully under section 412). [I'm presuming that in this context 'fault protection' is referring to section 411 rather than 434 - I don't think the wording is particularly clear]

    But back to the point... I might also add in 521.8.1 - conductors of a circuit not to be distributed over different cables/conduits etc. So in that context what 543.6.1 seems to be saying to me is: where earth fault currents are high then route the c.p.c. in the same way as a live conductor. You might also think of 521.5.1 that requires all conductors (incl. c.p.c.) to go through the same hole in ferrous enclosures etc.

    To me it all feels to be about the interaction of high fault currents - trying to keep the 'flow' and 'return' conductors close together so they cancel out as much as possible - and avoiding large separation of conductors that can cause lots of magnetic problems - from interference to increased loop impedances.

       - Andy.

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