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Mark P

1978 Sub-panel

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Do you know (based on the NEC) if a sub-panel installed in 1978 required the seperation of the grounds and neutrals with the neutrals floating - like today?

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A lot would depend on whether this was in the same building or a detached structure and if there were other metallic paths like a phoe or water line run between the 2 buildings. More info is needed.

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All in same building.

In that case, the sub panel grounding conductors and neutral conductors were supposed to be isolated. Just like today. My reference is the 1975 NEC, Article 250-61(b).

I can personally only trace this back to the 1947 NEC.

Douglas has traced it back further, but I'm not sure about the edition. For some reason 1923 sticks in my head.

Jim Katen, Oregon

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All in same building.

In that case, the sub panel grounding conductors and neutral conductors were supposed to be isolated. Just like today. My reference is the 1975 NEC, Article 250-61(b).

I can personally only trace this back to the 1947 NEC.

Douglas has traced it back further, but I'm not sure about the edition. For some reason 1923 sticks in my head.

Jim Katen, Oregon

Other than GECs, would there be any grounding conductors before 1947?

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All in same building.

In that case, the sub panel grounding conductors and neutral conductors were supposed to be isolated. Just like today. My reference is the 1975 NEC, Article 250-61(b).

I can personally only trace this back to the 1947 NEC.

Douglas has traced it back further, but I'm not sure about the edition. For some reason 1923 sticks in my head.

Jim Katen, Oregon

Other than GECs, would there be any grounding conductors before 1947?

Yes. While there weren't equipment grounding conductors as we know them today, many of the old electrical books discuss grounding of conduits, cable sheaths, cabinets, frames, & so on.

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For awhile there, the conduits and boxes WERE the equipment grounding method. My 1964 home was built with grounded receptacles (3 prong) which relied on conduits for grounding.

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