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Ground/Neutral Bonding Question


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Todays house had a 125amp service panel on the exterior and a distribution panel at the garage interior. There were no other panel boxes on the property, just one of those ground-mounted transformer boxes across the street (electric feed to the meter is underground lateral).

There are four wires coming into the service panel from the adjacent meter; two hots, a neutral and a solid copper ground wire. There is also an additional solid copper ground wire in the service panel, leading down to a grounding rod below the panel.

The thing that is stumping me is that the ground and neutral bars in the service panel are not bonded together. I am assuming that the ground/neutral bond is present at the transformer based on the 4-wire feeder from the meter. Is this okay or does the ground/neutral bond have to be accessible at the main service panel? Your thoughts please.

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Originally posted by JesseWBryant

Todays house had a 125amp service panel on the exterior and a distribution panel at the garage interior. There were no other panel boxes on the property, just one of those ground-mounted transformer boxes across the street (electric feed to the meter is underground lateral).

There are four wires coming into the service panel from the adjacent meter; two hots, a neutral and a solid copper ground wire. There is also an additional solid copper ground wire in the service panel, leading down to a grounding rod below the panel.

The thing that is stumping me is that the ground and neutral bars in the service panel are not bonded together. I am assuming that the ground/neutral bond is present at the transformer based on the 4-wire feeder from the meter. Is this okay or does the ground/neutral bond have to be accessible at the main service panel? Your thoughts please.

Ground and neutral are bonded together at the service equipment or the main and once you go downstream from the service equipment they are to be separate with the neutral floating and the ground bonded to the panel in the downstream panels.

Don't worry about the utility transformer, it has nothing to do with how the panel should be wired.

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Hi,

First, you need to describe it so that we can understand what you're asking.

You say there is a 125-amp "service panel" on the exterior and a "distribution panel" at the garage interior; don't you mean that there is a 125 amp "main disconnect" at the exterior of the garage and that there is a "sub-panel" inside the garage?

When you say there are 4 wires coming into the "service panel" from the meter are you referring to the "main disconnect"? It sounds like it; it also sounds like the driven service grounding electrode that the service grounding conductor is connected to is below the main disconnect; is that right? If so, that is correct.

When you talk about being stumped that the ground and neutral (grounded) bars in the "service panel" are not bonded together, is the panel you are referring to the main disconnect on the outside of the garage or the sub-panel inside the garage. If you're referring to the sub-panel, the ground bars and grounded bars are not supposed to be bonded in a sub-panel because the grounded conductors may not be bonded past the main disconnect.

Which is the panel that you are calling the "main service panel" in your last question?

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by hausdok

Hi,

First, you need to describe it so that we can understand what you're asking.

You say there is a 125-amp "service panel" on the exterior and a "distribution panel" at the garage interior; don't you mean that there is a 125 amp "main disconnect" at the exterior of the garage and that there is a "sub-panel" inside the garage?

When you say there are 4 wires coming into the "service panel" from the meter are you referring to the "main disconnect"? It sounds like it; it also sounds like the driven service grounding electrode that the service grounding conductor is connected to is below the main disconnect; is that right? If so, that is correct.

When you talk about being stumped that the ground and neutral (grounded) bars in the "service panel" are not bonded together, is the panel you are referring to the main disconnect on the outside of the garage or the sub-panel inside the garage. If you're referring to the sub-panel, the ground bars and grounded bars are not supposed to be bonded in a sub-panel because the grounded conductors may not be bonded past the main disconnect.

Which is the panel that you are calling the "main service panel" in your last question?

ONE TEAM - ONE FIGHT!!!

Mike

What he said!!! I was going to be mean, but suffice it to say that if you can't describe it to us, how can you report it to your client?

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I know it was a jumbled description. I was rushing in order to get it posted.

When I said main service panel I did mean main disconnect and I meant sub panel when I said distribution panel. I only used the other terms because I was reading through some posts yesterday and ran across one in which someone went to great length describing why you should not say "sub panel".

Anyway, I feel that the ground and neutrals should be bonded at the main disconnect panel but the ground wire coming in from the meter led me to believe that the bonding occurred elsewhere. So, even if it is bonded further upstream, it still needs to be bonded at the main disconnect for the structure....correct?

Thanks by the way.

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  • 1 month later...

The not bonding of ground and neutral and a separate ground wire to subpanels is done for the same reason you run a separate ground wire to an electric outlet!

So at an electric outlet, you would not connect (bond) the ground wire to the white (neutral) wire. You want a separate ground wire running back to the panel. Same thing with a subpanel.

It is for safety in case the neutral becomes disconnected (and there was no ground wire). Actually it is quite common for a neutral to become disconnected!

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Originally posted by JesseWBryant

I know it was a jumbled description. I was rushing in order to get it posted.

A humble observation: There's never a good reason to write a jumbled description, unless you're just making a jumbled note to yourself.

If you intend to convey information to others, you have to take the time to do the job correctly. Messing up the words is like messing up the nails -- things fall apart.

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Originally posted by thekctermite

The interior panel is a subpanel in this case, and the neutrals should be floated and there should not be any bonding. Bonding at a subpanel presents a hazard and is never acceptable.

I don't know if you wrote that exactly as you meant to, but there is bonding in a sub panel. The enclosure gets bonded to the equipment ground bar.

Brian G.

Bonding....Electrical Bonding [:-tophat][-crzwom]

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Originally posted by kurt

Not if one is using EMT and/or conduit (if the conduit is the ground path).

True enough, but the enclosure gets bonded one way or the other. Personally, I wouldn't trust EMT to be the ground. I ve seen too many runs come apart at the couplings. Rigid or IMC is a whole other thing.

Brian G.

I Sit Corrected (I'm Tired) [;)]

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Heck, this morning's inspection was a multi-unit with 4 electrical panels, each with individual 100 Amp/240 Volt service disconnects. One was for the main level unit, one was for the basement/common areas, the other two panels were for the 2nd and 3rd level individually. Inspection stickers indicate these were all installed Oct 2005.

The current owner has now combined the 2nd and 3rd level units into one living unit. He then had the main service disconnected in the panel labeled "3rd floor" and wire nutted the service cables within this panel. The panel labeled "2nd floor" has a 50 Amp double pole breaker feeding a 50 Amp double pole breaker in the panel labeled "3rd floor" to feed that panel.

The grounding and neutral (grounded) wiring in the "2nd floor" panel was still bonded at the terminal bars. Whomever modified this "2nd floor" panel forgot to separate the grounded (neutral) wiring from the terminal bar in the "2nd floor" panel. There was no metal conduit connecting the two panels, only 4 AWG 2 wire w/ ground Al cable. They should have used 3 wire with ground 4 AWG Al cable instead.

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