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I have a shed wired up with a fuse box with a main breaker, GFCI safety switch, breaker for light circut and breaker for outlets. The fuse box is wired with a common ground and neutral on a bar connection and the live wire running through the breakers.

When doing some work on the lights, I had the light circut off, but found that the GFCI would trigger then the wires were shorted. I suspect it is due to neutral and ground being unbroken, but can anyone advise if this is ok? Or is it indicitave of a bigger problem? I am in Australia and am on 240VAC if that makes a difference. Cheers

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  • Is there not a separate ground in the feed into the shed? Aug 30, 2021 at 3:34
  • There is a ground feed into the shed. This is combined with all the other grounds from the circuts into one big connector in the fuse box Aug 30, 2021 at 3:44
  • I take it neutral is also connected to that big connector, or is it on a different connector/bar? Aug 30, 2021 at 11:35
  • Pictures of the wiring in the box (with the cover carefully removed) would be most helpful. Edit your post and simply drag/drop the pics in, the site will upload, host & embed them in your post for you.
    – FreeMan
    Aug 30, 2021 at 12:40
  • Which pair(s) of conductors, when shorted, cause the GFCI to trigger?
    – Greg Hill
    Aug 30, 2021 at 15:39

1 Answer 1

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Any circuits fed off a GFCI or RCD device must have total monogamy between live and neutral wires.

Any load served by the hot must be served by the neutral. And vice versa.

Some amateurs are in the habit of "borrowing neutral" from any old circuit that happens to be nearby. Their logic being that neutral is like the chassis on a car with car wiring. Not at all. A neutral wire is no bigger than the partner live wire. Neutrals don't have fuses so this "monogamy" is a Code requirement - it's the only way to ensure the neutral is not overloaded.

It's a Code requirement on all circuits. GFCIs just keep you honest :)

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