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Say I have a #6/3 cable being spliced in a metal junction box. How would the (presumably stranded #8) ground wire be connected to the box?

  • I've seen a ~12ga bare wire crimped onto a larger conductor and then grounded, but I'm also interested to see what the "correct" way to do this is. – JPhi1618 Mar 1 at 19:10
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You can connect in much the same way you connect anything else. The only difference is the size of the wire nut. Something like a B-cap B4 Blue would do it, or you can just go with a small split bolt connector if you feel the wirenut would be over capacity.

By the way you don't use a #8 to the box since this is a bond not a grounding conductor. A #10 would be good for a 60A circuit if that is what the #6 is for. To bond to the box you could pigtail and attach to the box with a standard grounding screw (green) and use a crimp connector (spade, loop or some such).

NEC Table 250.122 Minimum size equipment grounding conductor. You size it off of the overcurrent Device. If you feel like doing some more reading you can go to 250 Part 5 Methods of equipment grounding which will refer you to 250.30(A)(1) and on and on and on. The gist of it is go to Table 250.122 and size it from there.

Good luck

  • @RetiredMasterElectrician it's a little more complicated, you size ground off the largest breaker the wire is allowed to use. That means if you upsize the wire, say for voltage drop, you must upsize the ground in harmony. – Harper Mar 1 at 21:39
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I would go with classic crimp ring terminals. Mind you, these can be stacked 2 or higher on a ground screw.

  • On a pigtail? (Link isn't loading a product for me.) What if I don't own a suitable crimping tool? – isherwood Mar 1 at 21:44
  • @isherwood Oh, McMaster! I bet they wonder why they're never listed in search engines, and Grainger is. Link fixed. But the crimp tool should be on your multi-stripper, if that won't suffice, that would be one of the rare times I would solder something in mains wiring (after first removing any plastic guard). – Harper Mar 1 at 21:49
  • On all the equipment that allows the hots to be soldered the ground is spicificly prohibited from a solder connection , usually a set screw or a crimp is the legal method, I have found 1 that allowed #8 lugs to be used 2 were required but they had to be under the same stud or nut and enclosed "rings" not forks. – Ed Beal Mar 1 at 23:45
  • @EdBeal whoops, OK, then mini-lug... Use the goop... – Harper Mar 2 at 0:00

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