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There is an addition to my 1960's house that still has the ungrounded two wire outlets, but the wire itself doesn't look bad.
The circuits on these two rooms are 15 amp each and have a combined 7 outlets and one ceiling light. One room with 4 outlets and one with 3 outlets and a ceiling light.

I want to extend a ground from another joining room's outlets, that are 3 prong grounded outlets, so I can install new 3 prong outlets.
If doing so, instead of using bare or green wire (and I will if it's the only correct way), can I just use Romex, but only use the ground conductor of it?
If so 14/2 or 12/2 circuit, as I have either available?
Or, since the rooms are over the area in the crawlspace where the 6ga ground connects to the plumbing, entering the house, should I clamp a ground to the pipe and start from there?

Here's a pic of the water pipe entrance, which is under room(s) in question. blurry image of copper plumbing going through a block foundation wall, connected to blue PEX, with a ground wire attached.

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  • Are you sure you don't actually have ground already available where you need it? In my house (1950s) so far every 2-wire receptacle I have replaced with a 3-wire receptacle already had ground available - it just wasn't being used! Commented Oct 23, 2022 at 16:33
  • Yeah, I've checked. There is not ground in these two rooms. It's like all they worried about grounding was the kitchen, dining and laundry area.....not so much on the bedrooms or the bathroom, for that matter.
    – Brad
    Commented Oct 23, 2022 at 16:40
  • Is the wiring NB or EMT conduit?
    – JACK
    Commented Oct 23, 2022 at 16:52
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    Either way is fine. The questions is what is easier for you. I know you answered this, but one more time. Are those outlet boxes metal or plastic? Did you check with multimeter between hot and the box
    – Traveler
    Commented Oct 23, 2022 at 17:50
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    Probably not an issue here but make sure your borrowed ground comes from the same panel as the circuit you are bringing it to. E.g. don't connect a ground from the subpanel to a circuit from your main panel.
    – JimmyJames
    Commented Oct 24, 2022 at 15:50

2 Answers 2

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The ground wire must follow any proper wiring method outlined in NEC Chapter 3. This could be an empty EMT conduit for instance. (I even posted a question on whether that empty conduit could then be used for telecomm LOL).

But there is no question that NM-B cable is a valid wiring method, it has a whole NEC article dedicated to it (Article 334). So a ground inside Romex is fine. Bit of a waste of money but sure. Also the conductors in the cable could be put to use for some purpose if the need arose. As such don't cut them off flush at the sheath - coil them up, cap them together and leave them in the back of the box. Remember all wires must be 6" long past end of cable sheath and come at least 3" out of the wall.

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All the options you suggest seem to conform to post-2014 Code, but there are important additional requirements for each (see below).

First, you are installing an "Equipment Grounding Conductor (EGC)", the important safety feature that routes fault current back to the electrical service connection in your electrical box (not to earth ground), so a breaker will trip and disconnect the fault. You don't want this new safety feature to be accidentally disconnected in the future, leaving the outlet unprotected without any visible notice! Thus, you should make it as clear as possible to future workers that this is an EGC and they should not cut or disconnect it at any point along its length.

2014 Code Language:

250.130(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions. The equipment grounding conductor of a grounding-type receptacle or a branch-circuit extension shall be permitted to be connected to any of the following:

(1) Any accessible point on the grounding electrode system as described in 250.50

(2) Any accessible point on the grounding electrode conductor

(3) The equipment grounding terminal bar within the enclosure where the branch circuit for the receptacle or branch circuit originates

(4) An equipment grounding conductor that is part of another branch circuit that originates from the enclosure where the branch circuit for the receptacle or branch circuit originates

(5) For grounded systems, the grounded service conductor within the service equipment enclosure

(6) For ungrounded systems, the grounding terminal bar within the service equipment enclosure.

Options:

  1. Connect to water pipe: While option 250.130(C)(1) above to connect to the Grounding Electrode System (your bonded water pipe in this case) is allowed, the connection back to your electrical box (not earth ground!) is indirect and any future failed/removed segment or bond along that path (e.g. replaced pipe or broken bond wire in crawl space) will leave your outlet unsafe without anyone knowing that. I would avoid this option.

  2. Connect to EGC from other circuit: This is the best option IMHO. However, the type of cable/wire used requires thought, because there are additional Code requirements for each type.

Issues:

  • An earlier Question/Answer suggested using bare-ground Armored Cable (spiral armor with a real bare copper ground wire inside) for this purpose, as it makes the issues below easier. You use it with MC/AC-type fittings. Earlier related Question

  • If you run Romex, (250.120(A)"where it [EGC] is a wire within a raceway or cable, ") you need to follow all the rules for running cable - proper terminations, listed clamps and fittings, support intervals, physical protection depending on where it is run, etc. You also should make it clear to future workers that the hot and neutral inside are not in use, but the ground IS.

  • If you run THHN or bare ground wire, you need to follow the rules for running an Equipment Ground Conductor on its own. 250.120(C) notes "(C) Equipment Grounding Conductors Smaller Than 6 AWG:
    Where not routed with circuit conductors as permitted in 250.130(C) and 250.134(A) Exception No. 2, equipment grounding conductors smaller than 6 AWG shall be protected from physical damage by an identified raceway or cable armor unless installed within hollow spaces of the framing members of buildings or structures and where not subject to physical damage." Bare ground AC covers the protection issue.

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  • Thank you. Appreciate the info.
    – Brad
    Commented Oct 23, 2022 at 19:36
  • You spoke of the water pipe issue: Connect to water pipe: While option 250.130(C)(1) above to connect to the Grounding Electrode System (your bonded water pipe in this case) is allowed, the connection back to your electrical box (not earth ground!) is indirect and any future failed/removed segment or bond along that path (e.g. replaced pipe or broken bond wire in crawl space) will leave your outlet unsafe without anyone knowing that. I would avoid this option. My ground is to the copper entrance pipe, next to the foundation. All of my plumbing from there into the house is PEX, if it matters.
    – Brad
    Commented Oct 23, 2022 at 20:23
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    @Brad correct, connecting to a water pipe is not legal. See NEC 110.2, equipment must be approved (by UL) and I seriously doubt UL approved that water pipe as an equipment grounding conductor. It would probably have to be factory-painted green w/ yellow stripe if it was so approved, and then plumbers would be educated to not break that grounding path. That is silly. Run a ground wire. Commented Oct 23, 2022 at 21:26
  • @Brad The issue for this is that pre-existing bonding wire from your copper water pipe to presumably your electrical box. If that connection doesn't exist (broken, removed, etc), then any EGC connected through that suddenly won't be an equipment ground any more. Separately, in terms of grounding to earth, there should probably be a bonding jumper across your water meter connections if that's by your house as opposed to out near the street. You probably already have grounding electrodes or similar by the electrical box, so using the copper water line for earthing wouldn't be an issue.
    – Armand
    Commented Oct 23, 2022 at 21:29
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    @Armand Sorry I misunderstood and thought they'd be clamping on the house side of the GEC water pipe tie. No you have a case there... but since they are near the bare grounding electrode wire, they could just use a split bolt to attach to that, which is unambiguously correct. Commented Oct 23, 2022 at 21:51

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