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wrong service panel ground?


Matt Fellman
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I'm looking for the neutral to ground bond in this service panel and am not thinking the ground wire in the neutral bus (right side) qualifies.

It's approved by the county and is new construction but I'm pretty sure it's wrong... Right side ground should be under green screw?

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I'm looking for the neutral to ground bond in this service panel and am not thinking the ground wire in the neutral bus (right side) qualifies.

It's approved by the county and is new construction but I'm pretty sure it's wrong... Right side ground should be under green screw?

To me, it looks like the left & right neutral bars are connected across the bottom. The green screw at lower left bonds them to the cabinet. The grounding bars are bonded to the neutral through the cabinet body.

At the left grounding terminal bar, what's the #4 stranded copper doing? If it's a grounding electrode conductor, it should be connected to the neutral terminal or there should be a jumper from the neutral bar to the grounding bar.

- Jim Katen, Oregon

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Thanks Jim,

The neutral buses are bonded via the metal strap between their lower ends.

There are two #4 copper grounds - one from the right neutral bus and one from the left ground bus. Both of these meet at the rebar bond beneath (and outside, of course) the panel.

What I'm looking for is the bonding of neutrals and grounds inside the panel. Is this accomplished by the green screw from below the left neutral bus being driven into the panel? (I didn't even check if it was tight).

Everytime I've seen a Sq D service panel like this in the past there's one of the copper #2 wires under that green screw. It just doesn't seem the screw through the neutral bus into the panel casing is much of a bond but I guess it may be.

The way the grounds and neutrals are on separate bus bars makes me think the electrician started off wiring this thinking it was a sub. It was signed off by Clackamas county and I hate to send everyone on a goose chase and end up being wrong.

Thanks again,

Matt

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Thanks Jim,

The neutral buses are bonded via the metal strap between their lower ends.

There are two #4 copper grounds - one from the right neutral bus and one from the left ground bus. Both of these meet at the rebar bond beneath (and outside, of course) the panel.

That's kind of odd. I see no harm in it, but the wire from the grounding bar to the rebar is unnecessary.

What I'm looking for is the bonding of neutrals and grounds inside the panel. Is this accomplished by the green screw from below the left neutral bus being driven into the panel? (I didn't even check if it was tight).

Yes. That green screw is adequate to serve as the connection for equipment grounds. (It isn't adequate for the grounding electrode conductor, but the real grounding electrode conductor is secured directly to the neutral bar.)

Everytime I've seen a Sq D service panel like this in the past there's one of the copper #2 wires under that green screw. It just doesn't seem the screw through the neutral bus into the panel casing is much of a bond but I guess it may be.

It's ok, but only for the equipment grounds.

The way the grounds and neutrals are on separate bus bars makes me think the electrician started off wiring this thinking it was a sub. It was signed off by Clackamas county and I hate to send everyone on a goose chase and end up being wrong.

It's curious but I think it's fine.

- Jim Katen, Oregon

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The large headed green screw on the left is the panel bond screw. There should not be a wire connected under that screw like you have seen in other panels. It screws directly into the metal enclosure. Terminating a wire under the screw would stop it from engaging the metal enclosure.

That cable feeding that panel looks like SE-R, not SE-U, based on the way the bare AL conductor looks. SE-U has the ground spirally wrapped around the two hot conductors. This one looks too tightly wound and does not appear to be individual strands. It looks factory braided.

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The large headed green screw on the left is the panel bond screw. There should not be a wire connected under that screw like you have seen in other panels. It screws directly into the metal enclosure. Terminating a wire under the screw would stop it from engaging the metal enclosure.

Agreed. I suspect that Matt is mistaken on that point. I can't recall having every seen a wire terminated under the green bonding screw.

That cable feeding that panel looks like SE-R, not SE-U, based on the way the bare AL conductor looks. SE-U has the ground spirally wrapped around the two hot conductors. This one looks too tightly wound and does not appear to be individual strands. It looks factory braided.

Now that you mention it, it does look like SER. But, if so, where's the neutral conductor? Did they cut off the neutral flush with the sheathing and use the grounding conductor for a neutral?

If it is SER, that might further Matt's theory that someone originally planned this as a sub panel.

- Jim Katen, Oregon

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Thanks guys... I think I am mistaken about how they are usually setup. I'll have to check out some I see in the future.

I talked to the county electrical inspector today and he agreed with the basic idea here... it's a bit odd but okay.

I'm glad I researched it through before I sent the report... I hate looking like a donkey's butt.

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Matt, is there a disconnect ahead of this panel?

No, definitely not

And, I have to concede.... I don't know the terminology of SEU vs. SER??

It's what you think. 3-wire vs. 4-wire. An easy way to remember is to think "Service Entrance Utility" and "Service Entrance Residential." You'd use SER for a sub panel.

And just for fun, there's also USE, which is rated for use underground.

I'm pretty confident this entry cable is a 2+1... I've seen a lot of the 3+1 with one of the "3" cut off and this isn't it.

Thanks

It just looks like it because the grey sheath isn't nice & oval the way that most SEU cables are. It's sort of lumpy-round, like SER. Could it be that they cut off the neutral and, in working with the cable, the cut neutral got drawn back into the sheath like a turtle's head into the shell?

- Jim Katen, Oregon

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