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Is this type of connection allowed according to the NEC assuming the ground wire is sheathed (like thhn) and striped back at the area of the screw and then continued to the receptacle ground screw then stripped there?

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  • Comment because I don't have a definitive answer about the NEC, but this is the preferred way to make connections to a screw+washer fitting in a ring-main in the UK. You have to be careful not to nick the copper when stripping the insulation of course. In this case, I would cut the insulation almost all the way through with a very sharp knife, and then grip it with pliars and pull, that would open the cut and slide the insulation along the wire a little. Then you just have to strip the end. (Possibly slide it a bit too far, cut the insulation, and slide back.) Commented May 24, 2019 at 9:57
  • Possible duplicate of Wire that was stripped inline and loops over the side screw
    – isherwood
    Commented May 24, 2019 at 13:12

2 Answers 2

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I'm not a fan. Several reasons. Remember the axiom of grounding (very similar to the axiom of neutrals in MWBCs):

Removing devices must not break continuity to other devices

Which in practice means they must be pigtailed.

This is sort of a "hybrid pigtail" where it is both pigtailed and not (Schroedinger's pigtail?)

Repeated removal/replacement of the rightside lamp could fatigue and break strands in that wire, injuring the ground going to the other lamp - that doesn't feel right. As an aside, it also fails to ground the junction box.

In the first picture, it's not so bad provided this is the supply cable, because removing that cable will render the whole box dead. But if you do it with any other cable, you have a problem because removing/replacing that cable will sever ground to equipment.

The right way, as always, is to pigtail to the metal box and to each piece of equipment, and join them in a splice; or take advantage of other means of grounding, such as in metal boxes: extra ground screws, "via screws" for switches, or "via hard flush contact" for receptacles.

Internal wiring to equipment is an exception

The situation in the second photo is a funny case, because it seems to be the interior of equipment which is sold, i.e. that looks like a multi-stalk security light. Equipment is not subject to NEC; it's subject to a different rulebook that is curated by Underwriter's Laboratories - who issues "UL Listings".

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It is a good method and some local jurisdictions require it, the wrap is required to be between 2/3 & 3/4 around the screw.

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  • Is this true for stranded wire as well?
    – isherwood
    Commented May 24, 2019 at 13:11
  • @isherwood Note that the pictured green wire is twisted considerably more than stock... that will help it not fray when the screw is tightened. If it frays, start over. Stranded on screws takes a knack... myself I stick the wire in the #8 bolt shear, and use that as a pliers to twist the wire tighter than I could by hand. Commented May 24, 2019 at 16:07
  • Yep. That's why I ask whether code allows it. Stock wire tends to spread when placed under a screw.
    – isherwood
    Commented May 24, 2019 at 16:17

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