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enter image description here Hello all,

I am adding a gfci breaker to my main breaker panel. By the looks of my panel I think the ground bus and neutral bus are bonded but not certain of this. It looks like my right bus bar is the neutral bus and the left is the ground bus. The copper wires coming in from the bottom and going to the right/neutral bus are bonded to ground rods. There is a flat metal strip running from the center of each bus bar to the center of the panel and I am thinking this is connecting both the neutral and ground bus bars together. I am wanting to check the following.

  1. Since my ground and neutral bars are connected I can treat them interchangeably when choosing where to place ground wires and neutral wires.
  2. Since I can treat the two bars interchangeably I can place the gfci pigtail and the incoming ground wire from the circuit I will hook it up to onto the same bus bar.

Thank you for your support and advice in this matter. Ben

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    Do NOT follow the example of the wire-trimming neatnik who has worked on the panel before. They are very proud of how neat and tidy the panel is, but they remove the ability to put any breaker/circuit in any position by chopping the wires so short. Leave enough wire to land it anywhere and zig-zag the excess up neatly.
    – Ecnerwal
    Mar 15, 2021 at 18:48
  • What does the panel labeling and instructions say about which one is ground vs neutral?
    – Harper - Reinstate Monica
    Mar 15, 2021 at 18:52
  • Harper, I couldn't find that info but from the looks of the right bus bar that is the neutral. It has the main neutral from the service entry connected to it.
    – Ben
    Mar 15, 2021 at 19:11
  • Look close at how the right bar connects to the crossbar: it's a removable grounding strap with a green screw, which goes into the panel casing. I also think the whole crossbar is uninsulated and probably bonded to the case as well. This would imply that the right bar is neutral, and the left bar ground when the bond is removed. Since this is a main panel and it is bonded, they're both ground/neutral bars, but whoever wired it up helpfully separated them in case you want to change it into a subpanel later.
    – Nate S.
    Mar 15, 2021 at 23:33

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Yep, you got it right. Main panels (not sub-panels) always have the ground and neutral bonded (connected). I prefer to put neutrals on the bus bar that can be isolated and is connected to the neutral conductor. The reasons for this is neutrals carry as much current as the hots and should have a good path. Not only that, if the main panel were ever to become a sub-panel (like behind a generator transfer switch), it's much easier to do that install.

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You need to consult the instructions and labeling of the panel.

"Electrical continuity" is not enough for a neutral bar. The current pathway must also be rated for full-load current, and that is mostly a thermal rating, i.e. can it carry full current without overheating? Lots of things that are good enough for a momentary 500A fault event are NOT good enough for a continuous 40A neutral load.

It is also common for main-breaker panels to be supplied with no grounds at all, you'd be expected to buy accessory ground bars if using it as a subpanel.

But they will always provide enough neutral lugs for the entire panel to be populated "maxed out" with 120V circuits. This looks like a 20-space panel (the breaker stabs to the right of the main breaker have been milled off so nothing can go there). I don't see any slots to accept tandem breakers, so this appears to be a 20-space/20-circuit panel. I count 16 screws on the right and 16 on the left. That's 32.

A slight variant of this panel (no main breaker; stabs not milled) was offered as a 24-space "main lug" panel*. That would require 24 neutral screws (1 neutral per lug, per Code) + 8 ground screws (3 per screw, per UL certification). That's just right for the main-lug variant. So I suspect both bars are intended for use as neutral... however, check the instructions and labeling: they are the last word on the subject.

UL approves the instructions and labeling as part of approving the panel.

* And if you ever want a generator interlock, that's food for thought. Find that version of this panel and swap bus assemblies (basically everything that isn't neutral bars, the whole shebang comes out with 2 screws). You don't even have to take the breakers off their wires, it's that easy. Then the top right 2 positions are populated and you can use it for the generator breaker w/ interlock.

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  • Thank you for your reply Harper. I will try to locate this info. So, if this were a main panel with two neutral bus bars would that mean in order to add a gfci breaker I would need to purchase and install a ground bus bar first?
    – Ben
    Mar 15, 2021 at 19:46
  • So, my panel is an Eaton BR2020B100 which has been discontinued. I got the manual for type CH and BR panels (mine is type BR) and it mentions hooking up the neutral and the picture shows the right side bus as the neutral. It further states to add the bonding strap to neitral if it is a main panel which it is. It shows the left side bus but does not indicate it is either ground or neutral. Concerning ground it simply states to refer to the NEC or CEC and applicable local codes for proper grounding methods.
    – Ben
    Mar 15, 2021 at 20:43
  • @Ben -- there's a white strap in the center of the panel, behind the backpan, that connects the two bars to each other, so they're both full-fledged neutral bars
    – ThreePhaseEel
    Mar 15, 2021 at 23:34
  • Yeah, whether the left bar is ground only or both ground and neutral depends on if the bond is present, so that's probably why they didn't label it as either.
    – Nate S.
    Mar 15, 2021 at 23:34
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    @ThreePhaseEel, I think the crossover strap is actually bonded to the case on this panel, and it only optionally bonds to the right side bar (if you zoom in there, you can see it's removable with one of those green screws), so I think left is always ground and right always neutral, and they're both either when bonded.
    – Nate S.
    Mar 15, 2021 at 23:36

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