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This is service main panel ( Square D QO load center) . I have to add total 9 breakers. 7 breaker on left and remaining 2 on right side.

enter image description here

I am seeing earlier electrician ( during construction) put some neutral wires in the ground bar but just only one under one screw.

So I can also attach, but this time is "Neutral pigtail wire" ( coming from breaker) to a ground bar under a different unoccupied screw. right ?

Another question: Earlier electrician put up to 4 ground wires under one screw. so following the same rule in two places as it was passed by inspector, and also it was easy for me and didn't find space. In picture, There are 2 screw on right side which already each had 3 ground wires under. so I added one more to each of two screw/lug.

so my question, why electrician didn't put 4 ground wire under other screws when electrician can do. Is there condition or situation when no. of ground wire under one screw vary ?

Thank!

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  • A passed inspection is not a guaranty that all issues were observed by an inspector, and laws such as app.leg.wa.gov/RCW/default.aspx?cite=19.28.361 relieve the inspector of liability for overlooked items. The NEC gives highest priority and requires complying with UL/CSA/ETL Listing, which covers labeling and instructions for proper installation.
    – NoSparksPlease
    Commented Aug 2, 2021 at 3:28
  • I would add one or two ground bars to this panel, given how full it is. There are (very likely) already mounting holes for them in the box, you just need to order the correct kit from Square-D (Schneider Electric.) You probably can rearrange to be safe and legal without doing that, but it's a convenience in a packed main panel (and a requirement in a sub-panel, but this isn't a sub-panel.)
    – Ecnerwal
    Commented Aug 2, 2021 at 16:12
  • There is still plenty of space left for my need . I don't and, think nobody as well, want to add a new ground bar for couple of wires.
    – user137442
    Commented Aug 2, 2021 at 16:24

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There aren't any ground bars in your photo. Those are all neutral bars.

It looks like they give you 52 normal neutral screw positions, plus 3 somewhat larger ones on bar #3.

Because this is a main panel, grounds are allowed on the neutral bar. Although you certainly put grounds on the ground bar if you prefer. Not every panel comes with ground bars installed, some require you to buy them as an accessory.

Some panels allow up to 3 grounds per lug position. You need to read the panel labeling to be sure of what they allow. You are never allowed to twist a whole bunch of grounds together and stick them on a large lug as if they are stranded wire.

Code requires exactly 1 neutral per lug position and they cannot share. Lots of pro electricians get that wrong.

It looks to me like the original installer put 4 grounds on some neutral lugs, and only 1 on others. You must correct the "too many" problems, and can feel free to consolidate the others to open up some neutral positions.

Or, simply install an accessory ground bar and put grounds there.

Also, all those tie-wraps. Read NEC 310.15(B)(3)(a) about thermal derate when >9 wires are bunched together, and either get rid of those tie wraps, or rewire with larger wires to satisfy the derate.

Do not nip off excess length of wires, you are better off with every hot and neutral being long enough to reach any space in the panel. That gives you freedom to move breakers around and to retrofit AFCI

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  • Thanks Harper, you mentioned "It looks to me like the original installer put 4 grounds on some neutral lugs, and only 1 on others". But I don't see only one ground on any lug. minimum is 2 ground on one lug. so you are saying 4 is too many on a single lug, how about 3 ?
    – user137442
    Commented Aug 2, 2021 at 1:14
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    @user137442 check the panel sticker. Which might be on the backside of the deadfront cover.
    – Harper - Reinstate Monica
    Commented Aug 2, 2021 at 1:22
  • What is the downside of "too many" ? I don't think there is any. its just make panel look nice and neat. I don't see there is code available which talk about limitation on no. of ground wire on one lug in main panel ?wire on lug in this case ?
    – user137442
    Commented Aug 2, 2021 at 16:26
  • @user137442 because UL tests equipment for safety, and approves the equipment and the labeling/instructions as a set. You might be right, but n+1 grounds on a lug has not been recommended by the company because it has been tested and found deficient, which is why they didn't ask UL to approve it.
    – Harper - Reinstate Monica
    Commented Aug 2, 2021 at 18:48

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