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I've installed a metal electrical box. There are 3 cables coming into the box. The standard box only has 2 ground screws. My inspector said I am supposed to have 1 single ground per screw...

So, how am I supposed to ground 3 cables then?

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  • Huh - all my standard boxes seem to think one grounding screw is perfectly adequate. I'm surprised your boxes have provision for a second one. – Ecnerwal Jun 1 '20 at 23:11
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Use a GROUND PIGTAIL. One end of the pigtail, the end with the terminal, goes under the grounding screw in the box. The other end is connected to your other ground wires with a wire nut of the appropriate size.

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  • Just to clarify, I can cut a piece of bare copper wire and use that, right? Quick internet searched turned up green-insulated wires for "ground pigtail" – Slav Jun 1 '20 at 17:39
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    Yes, the ground can be bare or green insulated. – jwh20 Jun 1 '20 at 17:47
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    @Slav - Indeed you can even purchase green insulated grounding pigtails that include the proper green colored ground screw attached. amazon.com/Gardner-Bender-GGP-1461-Grounding-Pigtail/dp/… – Michael Karas♦ Jun 1 '20 at 18:37
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You can drill and tap more #10-32 ground screw holes into the junction box, if you really want to.

That is the conventional size. You can use any thread pitch -32 or finer, and any bolt size #8 or larger. You cannot use sheet metal screws as their pitch is too coarse. Also, you cannot use mounting screws to pinch the ground wire between screw and case.

The ground screw does not need to be green.

Pigtailing is a basic skill you really need to know, as there are many problems that either require it, or it helps you avoid poor practice like using backstabs.

When pigtailing, the ground wire can be green or bare.

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