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Looking at my main service panel how can I tell if my ground and neutral bars are bonded (as they should be?) I obviously don't see a jumper wire between the two bars but I was troubleshooting and got confused as to why some of the ground wires are ran to the neutral bar (on the left)? I see the green screw on the left but it appears not to go anywhere. Any help would be greatly appreciated.

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  • Maybe a partial answer to my own dumb question the green screw on the left, is bonding the neutral bar to the case, the ground bar is attached to the case, so it is bonded via the actual panel case? Like following this picture?
    – BobDere87
    Commented Jul 22, 2023 at 2:29
  • Can you post a picture of the label on the inside of your panel's door please?
    – ThreePhaseEel
    Commented Jul 22, 2023 at 3:28
  • @BobDere87 that's quite likely. Post the label and we can confirm.
    – KMJ
    Commented Jul 22, 2023 at 4:05
  • I've seen those before, don't like them. Installed a short jumper between neutral and ground bars instead, which for a 100A panel is likely only copper #8 if feeders are #2 or smaller (see NEC 250.102).
    – NoSparksPlease
    Commented Jul 22, 2023 at 4:23
  • Also you have at least one breaker with a mismatched label, do make sure it is Listed as acceptable on panel cover or or the breaker is labelled as a "classified" replacement breaker. The NEC requires approval of a Nationally Recognized Testing Lab like UL or CSA.
    – NoSparksPlease
    Commented Jul 22, 2023 at 4:37

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The physical chassis of the breaker panel is grounded.

The ground strap tied to the green screw is tying the netural bar to the chassis of the panel. The accessory ground bar on the edge is also attached to the panel chassis.

In a main panel (service disconnect at the breaker) grounds are allowed as guests on the neutral bar.

I'm a little puzzled as to why I see so few grounds.

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  • The upper-right cables appear to be much older than the panel and without grounds. Some kind of rewire job gone wrong?
    – Robert Chapin
    Commented Jul 22, 2023 at 6:17
  • When installing a replacement panel most jurisdictions don't require replacing all the older wiring that was up to code when originally installed.
    – NoSparksPlease
    Commented Jul 22, 2023 at 15:05
  • It appears at some point (before we bought the house) previous owners had a new panel installed but kept a lot of old cloth covered romex (no ground wire). Ive been systematically going through and making these circuits safe with a gfci outlets.
    – BobDere87
    Commented Jul 23, 2023 at 4:08
  • What do you mean by allowed as guests? I am asking because the outlets that are grounded to the neutral bar are showing on my tester as no ground... so I was thinking I needed to move them to the ground bar.
    – BobDere87
    Commented Jul 23, 2023 at 4:11
  • @BobDere87 I mean when you have a ground (green or bare) wire, and it's the main panel, the green/bare ground is allowable on the neutral bar (though on the ground bar is best practice). The white wire is not ground.
    – Harper - Reinstate Monica
    Commented Jul 23, 2023 at 5:24

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