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I have just added a circuit to my main panel and saw something I wanted clarification on. For reference, my main panel is a Homeline 30 space panel with 2 extra grounding bars on the sides. Picture for reference.

Homeline 30space)

I know that in a main panel, you can have grounds and neutrals on the same bar, since they are bonded together at the main anyway. But doesn't that only pertain to the 2 inner neutral/ground bars, the ones that have the bonding screw. I found several neutral wires on the grounding bars on that are near the edges of the panel. From my understanding, wouldn't that be against code since the panel body is now carrying the return current for those particular circuits. In other words, should those 2 outer bars ONLY have grounding wires on them, while the 2 inner bars can have ground AND neutral wires.

Thanks for any input.

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It may sound funny but it is ok and even required in a way your neutral and ground being on the same bar is fine but look closer and you will see a jumper to ground (the panel is required to be grounded, your grounded and grounding conductors are tied together and then to the case so it is functionally the same on separate bars that are bonded and connected to the case.

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  • I get that neutral and ground are fine on the same bar if on the inside bars, but if they are on the outside bars, the only path for current takes it through the body of the panel. See attached picture at link. The faded white line is the path of current, so the metal body of the panel is being used to carry current. i.postimg.cc/fRMZdCxT/mspaint-BHTax-Qst-BB.png (For clarification, there is NO wire going from the far left bus bar to the main parts of the panel. The white faded line is to signify the path the current would take through the metal of the box)
    – IB - St. Louis
    Dec 31, 2019 at 23:10
  • Not just fine but required at the main panel. Code DID NOT require 4 wire until 99, from 1898 if I remember correctly. 3 wire systems were the standard until 1999 if my memory serves but I have only been doing this since the 70’s and have never known of more than a tingle on 3 wire. If you look closely at code over 80 years was consistent so keep asking questions and I am sure Harper will tell you what you want to listen to including the death mask on old ( by today’s standards) 3 wire systems. . . Code today is 4 wire. And has been since 99. Any deaths that you have heard of?
    – Ed Beal
    Jan 1, 2020 at 1:28
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You're absolutely right that a best practice is to separate neutrals and grounds. There are a bunch of reasons, but I'll give you one: you can replace your neutral-ground bonding screw with a bonding wire, and then stick a clamp ammeter around it. Voilà, ground faults are revealed!

However, this best-practice is not a Code requirement and you can't be written up for doing it the lazy way... in a main panel. This variation on Code was put there under pressure from builders, who didn't want to spring for panels with accessory ground bars. They said "it's all the same anyway, inside the main panel, and NFPA said "Alright, not worth fighting over".

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  • I'm with OP here, I don't like the idea of (potentially) 200A passing passing through that little green screw and sheetmetal... grounds on the neutral bar is 'fine', neutrals on the ground bars is less so.
    – SomeoneSomewhereSupportsMonica
    Jan 1, 2020 at 4:38
  • @SomeoneSomewhere Well the sheetmetal can certainly handle it, however I've had a panel inadvertently have no N-G bond because the screw, near as I can figure, vaporized. I like nice fat copper wires for N-G bonds.
    – Harper - Reinstate Monica
    Jan 1, 2020 at 4:46
  • The only thing that I can think of that would cause the bonding screw to "vaporize" would be current, and a ton of it, going through the box. I can't believe that the NEC would allow this.
    – IB - St. Louis
    Jan 1, 2020 at 5:02
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    @IB-St.Louis I fully expect it was not normal neutral flow, but a bolted ground fault of some kind.
    – Harper - Reinstate Monica
    Jan 1, 2020 at 5:03
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    @IB-St.Louis This panel has no ground wires, being all EMT; the neutral bar is the only bar. The N-G current was ground-fault current, something went ka-FLOOF in a big way. I discovered the burnup when I turned off a circuit I knew well, flashed hot to ground to triple-check, and got not the arc flash I was expecting. A fluorescent light on that circuit struck its arc and lit up! Turns out ground was at L1 potential the whole time due to another ground fault. That's when I discovered the N-G bond screw was only a screw head.
    – Harper - Reinstate Monica
    Jan 1, 2020 at 17:20
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It's not a good idea to run the neutrals to the enclosure attached ground bars for reasons other have mentioned. Although it's OK to run the grounds to the neutral buss bar, I prefer to keep them separated.

Also, note that on a SUB-panel, it's imperative the neutrals and grounds are separated and the neutral is NOT bonded to the enclosure. Instead, you need to feed a sub-panel with a 4 wire setup: 2 hots, a neutral and ground wires.

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I think an inspector could call out NEC 200.2(B) Continuity. The continuity of a grounded circuit conductor shall not depend on a connection to a metal enclosure, raceway, or cable armor.

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  • I was just looking at that and thinking it pertained to this. That is exactly what is happening. The path of continuity HAS to pass through the metal box enclosure in order for the circuit to work.
    – IB - St. Louis
    Jan 2, 2020 at 4:39
  • You might be able to install a bonding jumper between bars to get past that. The next question I always ask is UL installation Instructions, required stickers/labels, and embossed ground marks on the panel. Too much to consider when there are enough terminals to land neutrals on neutral bar and grounds on ground bar.
    – NoSparksPlease
    Jan 2, 2020 at 5:00

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