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I had a 20A circuit that was run to a work bench built by the previous owner of my home. I ended up replacing the work bench and replacing the circuit, with new THHN wiring all run through EMT conduit.

From the breaker box, I have ground, neutral and hot wires coming out of it which go to my first junction box. The box has a GFCI outlet. I then go a few feet horizontally to another junction box with a duplex outlet; repeating to the next box and the next.

I have my ground wire from the breaker box, connected to the ground screw on my junction box. This is also pig-tailed to the GFCI outlet, and then to another ground wire which leads to the next box. This next box is then grounded with the incoming ground wire and is also pig tailed to the outlet as well as the next outgoing ground wire.

Basically, I’m just realizing that since I am using all EMT conduit, I could technically just ground the first junction box/GFCI outlet with the ground wire from the breaker box right? Then for the rest of the junction boxes/outlets, the boxes would already be grounded so I could have saved myself from running a separate ground wire and just connect the outlet to the box correct?

My circuit is already wired up as previously described. Is it wrong of me NOT to have just relied on the circuit being grounded from the first junction box? Is it fine that I ran a separate ground wire to each box? I imagine it’s fine but I definitely could save some space in the box since the 12 gauge wires take up so much real estate. Any reason to open everything up and remove those ground wires or just leave it as is?

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    I hope you're not using #20 (20AWG) wire for a 20A circuit! I believe you meant #12 wire and just typo'd to "20Ga". If you did pull #20 wire, then it's definitely time to replace it all and save some money by not running a ground.
    – FreeMan
    Jul 29, 2021 at 18:34
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    Haha, sorry about that, I was running off very little sleep when I typed this. I fixed the typo, I ran 12 gauge.
    – ewrjontan
    Jul 30, 2021 at 11:18
  • Look at it this way: bad comes to worse, you know where you can find some copper.
    – A. I. Breveleri
    Jul 30, 2021 at 18:46
  • Remember, the legal code requirements are a minimum. You're completely okay going beyond those limits, as long as you don't fail to surpass them. Belt+braces+elastic waistband and your pants are unlikely to ever fall down.
    – Criggie
    Jul 30, 2021 at 23:58

4 Answers 4

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Yeah, what you did was "belt and suspenders". Doesn't hurt, doesn't help much.

Feel free to do that anytime you want. I tend to do it when I am concerned with physical damage to the EMT, e.g. from a wayward fork lift.

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    Also anywhere prone to corrosion. If the conduit runs round the outside of the wall or underground, assuming it will rust out eventually and taking appropriate precautions is a good thing.
    – Graham
    Jul 30, 2021 at 9:57
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    Also anywhere where there's a lot of generated electrical noise and you really want the extra-low impedance of a real ground wire to combat EMI. Often the supplemental grounding conductor in that case will be insulated so that a "clean" ground from the switchgear can star out to the equipment it is servicing. In a residential application, usually this would only matter for people with serious analog AV equipment.. In industrial, medical, or scientific installations it's somewhat more common and required.
    – J...
    Jul 30, 2021 at 12:52
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If the EMT conduit was installed with the proper connectors into a main panel that's properly grounded, then the EMT is all that's needed. Running the additional ground wire wasn't needed. There's no sense in going back and removing it, just make sure it's fastened to each junction box. If you continue the EMT in the future, don't run the ground wire. If you extend with NM cable, attach the bare ground wire from the cable to a grounding screw in the junction box.

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Often engineered drawings or specs will call out wires in addition to the raceways. The wires could be considered redundant if the conduit is installed properly, but they could be considered grounding assurance in case of failure due to damage such impact or seismic event.

What's not completely clear to me is it sounds like you may have run multiple wires in addition to the raceway, one to the first box, a second through the first directly to the second box, et cetera.

2020 Code Language:

250.148 Continuity of Equipment Grounding Conductors and Attachment in Boxes. If circuit conductors are spliced within a box or terminated on equipment within or supported by a box, all wire-type equipment grounding conductor(s) associated with any of those circuit conductors shall be connected within the box or to the box in accordance with 250.8 and 250.148(A) through (D)

(A) Connections and Splices. Connections and splices shall be made in accordance with 110.14(B) except that insulation shall not be required.

(B) Equipment Grounding Conductor Continuity. The arrangement of grounding connections shall be such that the disconnection or the removal of a luminaire, receptacle, or other device fed from the box does not interrupt the electrical continuity of the equipment grounding conductor(s) providing an effective ground-fault current path.

(C) Metal Boxes. A connection used for no other purpose shall be made between the metal box and the equipment grounding conductor(s) in accordance with 250.8.

(D) Nonmetallic Boxes. One or more equipment grounding conductors brought into a nonmetallic outlet box shall be arranged such that a connection can be made to any fitting or device in that box requiring connection to an equipment grounding conductor.

I think it means if you have separate unspliced circuits feeding separate receptacles you could run through a box with extra grounds, but if the wires are spliced or the receptacles from multiple boxes are fed by the same breaker or a multi-wire branch circuit (circuits that share a neutral) then you would need to connect all ground wires involved at each box.

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  • Hmmm, a little confusing. Reads to me like just the outlet would need to be grounded to the box?
    – ewrjontan
    Jul 30, 2021 at 11:31
  • I actually have two separate circuits running through the conduit (15A for lights and a 20A for tools) but I just simplified it in the main post. So at each box, I have a hot, neutral and ground for each circuit which connect to either an outlet or just the next set of wires that runs to the next box (for now while I wait on my lights).
    – ewrjontan
    Jul 30, 2021 at 11:41
  • @ewrjontan Added Code language for the box that I omitted for brevity. Also NEC 250.146 has requirement for grounding receptacle which include provisions for self grounding and surface metal boxes in 250.146, too long, didn't quote. If you think those may apply ask for details. You can read those full provisions on the NFPA (authors of the code) website by creating free profile at nfpa.org/codes-and-standards/all-codes-and-standards/…
    – NoSparksPlease
    Jul 30, 2021 at 16:03
  • Also re: "I could technically just ground the first junction box/GFCI outlet with the ground wire from the breaker box", conduit satisfies the ground requirement there too.
    – NoSparksPlease
    Jul 30, 2021 at 16:27
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If you are suggesting using the conduit as a ground, not all versions of the NEC allow that, so doing so would depend on the version of the NEC applicable. I would recommend against doing so as some conduit to box connections are not electrically reliable.

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    There are only a couple of circumstances where the NEC requires a wire-type GEC (some situations with pools and other corrosive environments, and when threadless/compression type fittings are used with rooftop conduits) due to potential for chemical or physical damage to metal conduits. Otherwise, UL tests and lists conduit-to-box fittings for grounding continuity, and you can use a bonding jumper from a bushing to a grounding screw/junction/bar if you're truly paranoid...
    – ThreePhaseEel
    Jul 31, 2021 at 0:19
  • It has been a while but I have been dinged for not having grounds in emt with full bonding, so I got a copy to the relevant years nec and sure enough the inspector was right. also I have spent hours troubleshooting bad conduit grounds.
    – hildred
    Jul 31, 2021 at 0:36
  • I suspect it was the accessible-rooftop stuff that got you dinged then
    – ThreePhaseEel
    Jul 31, 2021 at 0:44
  • Nope, indoor dry church auditorium.
    – hildred
    Aug 4, 2021 at 20:48
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    Interesting -- Article 518 in the 2017 NEC does permit conduit to be used as the grounding means in an assembly occupancy, so maybe what you ran into was a local amendment?
    – ThreePhaseEel
    Aug 4, 2021 at 23:02

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