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I have an older home where some of the house has updated electrical and some doesn't.

In a few rooms I still have several of the 2 prong outlets with no ground wire in the box and I want to replace them with 3 prong tamper proof outlets with proper grounding.

If I had an easy way to run a new line from the panel I would not be wasting your time, but I live in a split level home and several of these rooms have their lines fed from below, in-between floors, so I don't have any way to run a new line easily.

I know I can add GFCI outlets for some human protection but I want to do better.

I need to know if it is safe and/or legal to run a ground wire from a junction box in my attic (there are several) down the wall to use as ground when I replace the 2 prong with a 3 prong. The junction box likely leads back to a different circuit but it is all originating from the same panel (I only have 1)

  • Where would this ground wire be run to? – ThreePhaseEel Aug 23 '18 at 23:08
  • Ground wire would run down the wall and be connected directly to the ground screw of a new 3 prong outlet that will replace the old 2 prong. So, from junction box directly to outlet. From the junction box, the existing ground goes back to the panel. – ctorx Aug 23 '18 at 23:12
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This is fine, provided you're under a new enough Code

The 2014 NEC added a new point 4 in 250.130(C):

(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

that, along with 250.134(B) exception 1:

Exception No. 1: As provided in 250.130(C), the equipment grounding conductor shall be permitted to be run separately from the circuit conductors.

lets you do precisely what you are describing (running a separate ground wire to an existing point on the equipment grounding system originating from the same panel).

The minimum wire needed for this is a 14AWG bare or green (THHN) wire, but I would use a Bare Armored Ground cable instead (to make it clear to future remodelers that this isn't something they can just cut through willy-nilly). You will also need the Bare Armored Ground cable if it's exposed to physical damage to comply with the protection requirements of 250.120(C).

  • Thank you for the detailed explanation. What exactly do you mean by "provided you're under a new enough Code" ? Does it depend on where you live and what the state/county allows? – ctorx Aug 24 '18 at 1:05
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    @ctorx exactly -- your state/county/city needs to have adopted the 2014 or 2017 NEC to permit this – ThreePhaseEel Aug 24 '18 at 1:12
  • Although if they haven't, and you go ask your inspector "hey, can I do this? It's permitted in 2014 code" you are bound to get a yes. – Harper Aug 24 '18 at 12:48
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    @ctorx -- indeed it does – ThreePhaseEel Aug 24 '18 at 22:10
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    Great question and discussion here. The only thing I can add is the requirement in 250.120 (C), for EGC's smaller than #6 to make sure they are adequately "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 physical to subject damage." I'm in a similar situation with my older home and plan on running #12 solid down the walls from each 15a & 20a receptacle outlet to attic junction boxes run from there back to the panel, stapling and routing them along the corners. – Nicknamednick Sep 3 '18 at 0:22

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