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Is it NEC compliant to wrap the ground wire from a 14-2 around the sheathing and then clamp it using the NM clamp in a metal junction box? I live in a house built in the 60s and I see that a lot but I don't know if that's sufficient for grounding.

There are two use cases in particular that I'm curious about for this style of grounding.

The first use case is receptacles. Say you have an incoming and outgoing cable both with the grounds wrapped and clamped, then the receptacle is attached to the box with a ground screw (e.g. not spliced to the incoming/outgoing grounds). Is everything grounded properly or does the receptacle need to be spliced together with the ground wires directly?

The second is lighting. Basically the same question; if the cable grounds are wrapped and clamped, can the light be grounded directly to the box or does it need to be spliced with the ground wires directly?

In either case, if you splice the grounds do you also need to have a connection to the box?

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  • With a metal box yes it needs to be connected to the grounds even if they are all connected together. I have not seen a clamp used . More often all the grounds were required to have a common non reversible crimp and a connection to the box. Electrically speaking it would work but I would want them all connected together with a minimum of a wire-nut. – Ed Beal May 10 '20 at 6:02
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No, that's a "cowboy move" - there are 10-32 threaded holes in virtually every metal box specifically for a grounding screw, and using the cable clamp as a ground connection is not compliant/listed/correct.

The ground wires should all be connected to each other and to that grounding screw. In the unlikely event that your boxes don't have a pre-threaded hole there are thread-forming grounding screws available, but generally you just need to grab a bag of short 10-32 screws (you can find green ones in the electrical aisle, but they don't have to be green.) They specifically need to be the "-32" or fine thread variant so that they have sufficient threads in the box metal - and really, if you look carefully, you will almost always find that hole in the box ready for it.

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  • The smallest hole in the box.+ – JACK May 10 '20 at 14:26

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