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Jurisdiction

Kentucky, USA; 2017 NEC / NFPA 70

Background

I live in a house built in the 50s that was originally wired with ungrounded outlets. Many parts of the house have been rewired, but a room that I'd like to use as a home office still has only ungrounded receptacles. I'd like to convert at least one of these to a grounded receptacle.

The receptacle in question is on the 1st floor, on an exterior wall; is fed by cloth sheathed conductors (not in conduit); and is contained within a metal outlet box. In the basement just below, there is a grounding electrode conductor (GEC) of bare copper, probably 6 or 8 gauge, running within a few feet of the outlet. I think it will be possible to fish a cable from the GEC to the location of the outlet, following the same path as the existing conductors.

What I'd like to do is keep using the existing conductors for hot and neutral, and run a separate equipment grounding conductor between the GEC and the outlet, as allowed by NEC 300.3(B)(2) and 250.130(C)(2). I'm planning to use 12-AWG solid green copper THHN wire in accordance with NEC 250.122A (size), and 310.6(C) and 250.119 (insulation/covering and color). I haven't found any code requirements as to stranded vs solid or to insulated vs covered vs bare. I decided on solid and insulated because I thought it would better withstand the fishing process and being nearby the existing conductors. I'm planning to replace the old box with a PVC old work box.

Question:

How do I connect my new ground to the GEC?

I think the answer is probably a split bolt connector, sized based on the larger wire, not insulated or wrapped, and not in a junction box. But I haven't had much luck finding code citations that support that choice.

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  • Old/new metal boxes are liked more than the plastic boxes. They do not need a separate/extra ground wire to the switch/outlet/receptacle.
    – crip659
    Commented Aug 18, 2023 at 21:55
  • @crip659 I thought exactly the opposite was true: for a plastic box all I need to do is connect my ground to the receptacle, for a metal box I would need to connect my ground to the box and then connect my receptacle to my box. Am I missing something?
    – scott
    Commented Aug 18, 2023 at 22:10
  • The good receptacles are self grounding to a grounded electrical box. The metal boxes also have a few other benefits that people like, over plastic, but both are code approved and comes down to what the person prefers/has handy. I know new code allows you to connect an added ground to a close grounded circuit back to the panel, but I think connecting to the GEC is different.
    – crip659
    Commented Aug 18, 2023 at 22:23
  • 1
    @crip659 I didn't know about self-grounding receptacles, I'll take a look, thanks for the suggestion. Connecting to the GEC is allowed, take a look at 250.130, and paragraphs (C) and (C)(2) within. In relevant part: "For replacement of non-grounding-type receptacles with grounding-type receptacles... The equipment grounding conductor of a grounding-type receptacle... shall be permitted to be connected to any of the following:... Any accessible point on the grounding electrode conductor."
    – scott
    Commented Aug 19, 2023 at 0:00
  • Is it OK to borrow a ground wire from a different circuit? "as long as it originates from the same enclosure"
    – Mazura
    Commented Aug 19, 2023 at 20:19

2 Answers 2

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This is easier than it sounds

Connecting to a bare grounding equipment conductor without cutting it sounds like a challenge, but it isn't with the right parts. An Ilsco GTT-2-2 or equivalent lay-in T-tap connector is what I recommend, as it's somewhat less fiddly to install than a split bolt; just remember to torque it to spec!

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The relevant code is the one that says you cannot cut the GEC.

That limits you to non-cutting splice methods such as, sure, a split bolt.

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