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Should the bonding screw be installed


Mark P
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Main disconnect in the system is outside by the meter, since it is the 1st over-current protection in the system it is the main. The distribution panel is inside the house where there is also a 100 amp disconnect.

1st question: Is the inside distribution panel considered a sub-panel? The longer I analyze it the more I keep flip-flopping, but at this moment I’m thinking it is, because the main is outside.

2nd question: If the outside box is the main and the inside a sub, then is the bare copper wire at the bottom of the outside box the bond? If this is the bond then the bonding screw should not be installed in the distribution box (which it is not), and the two circuit grounds (white wires) connected to the left side neutral busbar should be isolated on the other (right side) neutral busbar with all the other grounds. Correct?

3rd: Now if I’m wrong and the inside box is not a sub-panel, then the bonding screw does need to be installed?

So all this started with the question: Install the bonding screw or not.

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Hi Mark,

Personally, if I saw it, I'd write it for lack of bonding screw in the disconnect enclosure and for the fact that the grounded (neutral) conductors and the equipment-grounding (grounds) aren't isolated from one another in the sub-panel (the one with most of the breakers). I'd do that because the rule is anything past the main disconnect....etc.

However, that's me and maybe I'm being too picky. After all, the enclosure to the main disconnect is joined to the other enclosure with a length of metal conduit and the feeders between the disconnect and the inside panel are essentially just extensions of the connections in the larger panel. Given the fact that the metal conduit makes the two panel enclosures essentially the same enclosure, if the green bonding screw were inserted in the center of that main connector between the left and right buses in the interior panel, I think you'd have a perfectly safe, although slightly unorthodox setup.

Now watch Jim Katen or Mark Cramer come in here and jackslap me upside the head for saying something Homerish. [:-dunce]

ONE TEAM - ONE FIGHT!!!

Mike

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Hi Mark:

Since the box in your top photo is the first disconnect after the meter, this first box is the MAIN disconnect and where the bonding screw should be installed to bond the grounded and grounding wires.

Everything downstream from this MAIN disconnect would be considered an auxiliary or 'sub panel' and therefore should NOT have bonding screws installed. As Mike noted above, the grounded (neutral) wires need to float in this subpanel and not be connected to the panel or any grounding wires. Of course, the grounding wires in these subpanels must be bonded to the panel.

Matt

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What I'm seeing is that the outside box has the insulated neutral and a bare grounding wire just passing through at the bottom without any other connections there. This looks like no more than an exterior disconnect for the inside panel but it sure isn't wired as the service disconnect. The jumper at that panel is bonding the conduit and box , but not doing much else.

Is this a separate structure or apartment fed from a main house (with its own private meter for the tenants)? Is it possible that there is another panel (the actual service disconnect) upstream from this where that "pass through" neutral and ground are bonded together and a GEC then goes to an electrode?

Do you have a wider photo of the exterior? I'd like to see the meter box and how that is fed from the utility.

As for the inside panel...both the left and right neutral/ground bars are connected by the bar across the top. Moving wires from left to right wouldn't accomplish anything. To wire this correctly would typically require installation of another and separate grounding bar with all grounding conductors moved to that.

PS..."two circuit grounds (white wires)". Mark, whites are normally neutrals or grounded conductors. Circuit grounds would be the bare grounding conductors.

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This is a single family home with no garage or other detached building. The service is overhead and there is no disconnect upstream of the outside disconnect. The schematic picture is from the outside box.

I see now that the jumper cable in the outside box is just that and not a form of bonding. So the system is not bonded at all and needs to be. Now my question is should the bonding screw be installed in the inside box or outside box?

If one considers the inside distribution panel as truly a sub-panel then the grounds and neutral are not properly isolated and in order to isolate them (according to Richard) another grounding bar would need to be installed and the bonding screw would be installed outside.

If one does not consider the inside distribution panel as a sub, but as the main with an additional disconnect outside, then all that needs to be done is install the bonding screw, somewhere.

One thing is for sure, I have no fricking idea. Since there was a faulty breaker (would not stay in on position) I called for a sparky to fix that and while he is at it determine if bonding screw needs to be installed or not. This was brand new service in a remodeled home.

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Hi Mark,

We aren't supposed to presuppose what a sparky will say or do. The textbook answer, as I said above, is that the outside disconnect is the main panel and the inside panel is a sub-panel. Given that, you have to separate the grounded conductors and equipment-grounding conductors on separate buses by adding an equipment-grounding bus and then install a bonding screw in the appropriate location on the exterior enclosure, exactly as Richard states above. That's the way you write it.

The reality is that what will then most-probably happen is a sparky will come out, make some comment about "Idiotic friggin home inspectors don't know their a** from a hole in the ground," and will install the bonding screw in that hole at the strap between the two neutral buses at the top of the inner panel, replace the faulty breaker, close the panel up, and walk away. Because the two panels are joined by that metal hub and conduit, I don't think it will make a bit of difference to the electricity passing through there. If something happens, it will still do exactly what it is supposed to do in a perfect scenario, albeit in a not-so-perfect way.

That is going to be the sparky's call and when he makes it you should simply shrug your shoulders and say, "He's the electrician, not me; it's his call." Just explain to the client that you are the family doctor and that the sparky is the brain surgeon; if the sparky chooses to make an unorthodox call it's on him, not you.

Whatever you do, stay out of it from the point where the sparky gets involved. Don't dispute the sparky's work unless you want to become ensnared for practicing as an electrician without having an electricians license. Just document every conversation and archive every email related to the issue and make sure the client understands that you've washed your hands of it once the sparky touches it.

ONE TEAM - ONE FIGHT!!!

Mike

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This becomes a lot easier to understand once you get some basic terminology straight in your mind. This definition comes straight out of my code book:

"SERVICE EQUIPMENT. The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s), and their accessories, connected to the load end of the service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply."

Look for the first point in the system after the service drop (overhead) or service lateral (underground) where you can turn off the entire power to the home in six throws or less. That's the service equipment. Sometimes you'll find the service equipment in an enclosure by itself but usually it is in the same enclosure with the branch circuit distribution panel (commonly called the "main panel"). Wherever you find the service equipment, that is where the neutrals (grounded conductors) and grounds (grounding conductors) need to be bonded together. Downstream of the service equipment, the neutrals and grounds need to be kept separate.

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Mark, my final take on this after looking at the wide angle shot:

It looks like a GEC coming from the meter base connected to a ground rod(?). I would suspect that the grounding and neutral bond is made at that panel and that the combination of the meter and exterior disconnect panel would be considered the service equipment. It's an unusual configuration (at least around here) but I see no harm in it. Of course, you can't actually see the connections at the meter base.

So...recommend the grounds and neutrals be separated at the interior panel (along with any needed extra grounding bar) and have the electrician check the bonding/GEC/grounding status at the exterior at the same time.

As Mike said, it's not a real scary hazard the way it is, but neutral current is passing between the interior panel and the utility grounded conductor along the bare grounding wire as well as the insulated neutral. The conduit between the panels is also in play but it seems unlikely that would be an "attractive" path for current. My guess is that it would take some freakish circumstances for this to actually harm anyone, but, it is wrong. The good news is that it is very easily corrected.

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Originally posted by AHIS

Main disconnect in the system is outside by the meter, since it is the 1st over-current protection in the system it is the main. The distribution panel is inside the house where there is also a 100 amp disconnect.

On the outdoor panel's label, do you see the words, "Suitable for use as service equipment?" If so, this is the service equipment for the house. The first thing that jumps out at me is that the neutral (grounded conductor) doesn't land in the box. It's supposed to. (230.75)

That little omission would cause me to question everything else I saw in this installation. It would also prompt me to tell my customer that this service was probably not installed with a permit. I'd tell the customer to ensure the electrical system is permitted and that it's passed its final inspection.

1st question: Is the inside distribution panel considered a sub-panel? The longer I analyze it the more I keep flip-flopping, but at this moment I’m thinking it is, because the main is outside.

Yes. It's a sub panel.

2nd question: If the outside box is the main and the inside a sub, then is the bare copper wire at the bottom of the outside box the bond?

No. It can't be *the* bond because there's no neutral in this box to bond to.

If this is the bond then the bonding screw should not be installed in the distribution box (which it is not), and the two circuit grounds (white wires) connected to the left side neutral busbar should be isolated on the other (right side) neutral busbar with all the other grounds. Correct?

An electrician should install a grounding terminal bar kit in the indoor panel and put all of the equipment grounding conductors there. Of course, he'll need four conductors between the outside box and the inside box. The conduit can be the grounding conductor.

3rd: Now if I’m wrong and the inside box is not a sub-panel, then the bonding screw does need to be installed?

You're not wrong and the screw should stay there lying at the bottom of the enclosure.

- Jim Katen, Oregon

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