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That's a good question. I have run into that same setup a few times before. I thank the technical answer is yes, it is a sub panel.

The two panels are so close and bonded together by the conduit connection I believe there is no practical reason it wont't work properly as is.

As far as calling it out as a defect I probably wouldn't if that was the only thing wrong with the panels.

I sure someone else can give you a more technical answer.

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I think if your EGCs for the circuits originating from the smaller panel are using the neutral bus in the main panel then you don't need 4 wire service to that smaller panel. One catch is concentric rings on either panel where that short piece of conduit penetrates. If there are concentric rings on either end then you need 4 wire service to the smaller panel.

The presence of concentric rings prevents that metal conduit from doubling as bonding conductor to the smaller enclosure.

That's my guess.

Marc

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I think if your EGCs for the circuits originating from the smaller panel are using the neutral bus in the main panel then you don't need 4 wire service to that smaller panel. One catch is concentric rings on either panel where that short piece of conduit penetrates. If there are concentric rings on either end then you need 4 wire service to the smaller panel.

The presence of concentric rings prevents that metal conduit from doubling as bonding conductor to the smaller enclosure.

That's my guess.

Marc

I disagree. The neutrals and grounds should be separated in the second panel. If I found that they routed the neutrals from the second panel into the first, I'd call it a defect. All conductors of a given circuit are supposed to travel together per 300.3(B). If you routed the neutrals separately, the hot wires would induce current in the nipple.

As far as I know, the concentric knockouts only present a problem on the supply side of the service. They shouldn't be a concern on the load side. If you've got a reference that says otherwise, hit me with it.

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Could somebody explain again about the concentric ring thing messing things up?

I dunno exactly but there's a practice involving metal conduit between meter box and panel: If there are concentric rings left on either the meter box or panel enclosure after installing the conduit, a bonding wire must be run through the conduit from meter box to a grounding/locking bushing on the panel side I guess because the remaining concentric rings are easily damaged and are therefore not a reliable bonding connection.

Marc

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I think if your EGCs for the circuits originating from the smaller panel are using the neutral bus in the main panel then you don't need 4 wire service to that smaller panel. One catch is concentric rings on either panel where that short piece of conduit penetrates. If there are concentric rings on either end then you need 4 wire service to the smaller panel.

The presence of concentric rings prevents that metal conduit from doubling as bonding conductor to the smaller enclosure.

That's my guess.

Marc

I disagree. The neutrals and grounds should be separated in the second panel. If I found that they routed the neutrals from the second panel into the first, I'd call it a defect. All conductors of a given circuit are supposed to travel together per 300.3(B). If you routed the neutrals separately, the hot wires would induce current in the nipple.

As far as I know, the concentric knockouts only present a problem on the supply side of the service. They shouldn't be a concern on the load side. If you've got a reference that says otherwise, hit me with it.

I should have explained a little better.

I didn't mean routing neutrals from the smaller panel, I meant rerouting the EGCs of circuits originating in the smaller panel to the neutral in the main panel. In the main panel the neutral bus and the EGC bus are the same. I say this because it appears to me in the photo that ALL EGCs, from both panels, are tied in at the main panel neutral bus. I may be wrong but that seems to be what's going on.

Marc

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What Jim said, it is wrong to run the neutrals out of the small box into the big one. Reason would be too easy for a neutral wire to be disconnected by mistake.

They are feeding it like a sub panel, so they need to wire it like one.

The concentric rings thing makes sense. But where conduit is used for branch circuits, there doesn't seem to be a problem, or is there?

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. . . I didn't mean routing neutrals from the smaller panel, I meant rerouting the EGCs of circuits originating in the smaller panel to the neutral in the main panel. In the main panel the neutral bus and the EGC bus are the same. I say this because it appears to me in the photo that ALL EGCs, from both panels, are tied in at the main panel neutral bus. I may be wrong but that seems to be what's going on.

Sure, that's what's going on. That's how all sub panels are set up. People have often used this as an excuse to not separate the neutrals and the grounds in a sub panel (Hey, they're connected at the service panel anyway. . .)

It's wired wrong, plain and simple.

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Could somebody explain again about the concentric ring thing messing things up?

I dunno exactly but there's a practice involving metal conduit between meter box and panel: If there are concentric rings left on either the meter box or panel enclosure after installing the conduit, a bonding wire must be run through the conduit from meter box to a grounding/locking bushing on the panel side I guess because the remaining concentric rings are easily damaged and are therefore not a reliable bonding connection.

Marc

That's basically it, but it only applies to the connection at the service panel. As far as I know, you don't have to worry about it after that.

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Could somebody explain again about the concentric ring thing messing things up?

I dunno exactly but there's a practice involving metal conduit between meter box and panel: If there are concentric rings left on either the meter box or panel enclosure after installing the conduit, a bonding wire must be run through the conduit from meter box to a grounding/locking bushing on the panel side I guess because the remaining concentric rings are easily damaged and are therefore not a reliable bonding connection.

Marc

That's basically it, but it only applies to the connection at the service panel. As far as I know, you don't have to worry about it after that.

...so the knockouts, isolated so much by their nearly all around cuts, don't have enough area in common with the box to make a bond.

BTW what happened to the red wire feeding the sub? I only see black ones coming in there, with one taped white.

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Could somebody explain again about the concentric ring thing messing things up?

I dunno exactly but there's a practice involving metal conduit between meter box and panel: If there are concentric rings left on either the meter box or panel enclosure after installing the conduit, a bonding wire must be run through the conduit from meter box to a grounding/locking bushing on the panel side I guess because the remaining concentric rings are easily damaged and are therefore not a reliable bonding connection.

Marc

That's basically it, but it only applies to the connection at the service panel. As far as I know, you don't have to worry about it after that.

...so the knockouts, isolated so much by their nearly all around cuts, don't have enough area in common with the box to make a bond.

BTW what happened to the red wire feeding the sub? I only see black ones coming in there, with one taped white.

There is no red conductor for the feed. There ar two blacks, one behind the other. The other arguments throughout the thread about eccentric or concentric knockouts is moot for voltages under 250.

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Could somebody explain again about the concentric ring thing messing things up?

I dunno exactly but there's a practice involving metal conduit between meter box and panel: If there are concentric rings left on either the meter box or panel enclosure after installing the conduit, a bonding wire must be run through the conduit from meter box to a grounding/locking bushing on the panel side I guess because the remaining concentric rings are easily damaged and are therefore not a reliable bonding connection.

I disagree, although I always include an EGC within metallic raceways.

Marc

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the concentric knockouts may not 'sustain fault current' and the 'connection' could fail.. due to the inherent stamped-in weak-points.. They might not 'clear the fault'.. Right?

Sounds like it. But I wouldn't use that for boilerplate.

Marc

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the concentric knockouts may not 'sustain fault current' and the 'connection' could fail.. due to the inherent stamped-in weak-points.. They might not 'clear the fault'.. Right?

The concentric knockouts can sustain a fault current just fine - particularly for the brief fraction of a second that they need to.

The problem with concentric knockouts ON THE SUPPLY (LINE) SIDE OF THE SERVICE ONLY (That is, where the service conductors enter the service panel.) is that the concentric knockouts can be damaged and come entirely apart, after which they won't sustain any current at all. This is a particular concern on the supply side because there are no fuses or breakers protecting that part of the installation.

One more time:

As far as I know, there's no problem with having concentric rings as part of the equipment grounding path *after* the service panel.

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