Why did the inspector make me bond neutral to ground?

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Mrat

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I recently installed a subpanel in a new garage which is fed from a pool subpanel which is fed from the meter/main. The new garage has a ufer ground that I installed a ground wire to. The pool panel feeds the garage subpanel with a 2 pole 40 amp breaker. I failed my inspection because the screw in the neutral bus bar that connects it to the sub panel enclosure and thus the ground buss bar was not bonding the neutral to the ground. Why is this done? I was not there to quiz the inspector. The garage is detached and separate from the house. The pool subpanel is fed with 4 wires H-H-N-G as is the garage subpanel. Can you explain why this is done? I have tried to look at posts going back to 2003 in this topic without luck. I appreciate your responses. Mark
 
Mrat said:
I recently installed a subpanel in a new garage which is fed from a pool subpanel which is fed from the meter/main. The new garage has a ufer ground that I installed a ground wire to. The pool panel feeds the garage subpanel with a 2 pole 40 amp breaker. I failed my inspection because the screw in the neutral bus bar that connects it to the sub panel enclosure and thus the ground buss bar was not bonding the neutral to the ground. Why is this done? I was not there to quiz the inspector. The garage is detached and separate from the house. The pool subpanel is fed with 4 wires H-H-N-G as is the garage subpanel. Can you explain why this is done? I have tried to look at posts going back to 2003 in this topic without luck. I appreciate your responses. Mark
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I'm a little confused here. From your description, it sounds to me like the neutral and ground bars were bonded, which would be a problem in a subpanel. But you also seem to say that the subpanel failed because the neutral was not bonded.

The only place you bond the neutral to the ground is in the main panel. Neutrals and grounds are to be kept separate everywhere else downstream. If the inspector is telling you to connect the neutral and ground bars in a subpanel, he's wrong. Unfortunately, my brain isn't very quick with code references this late. Anyone? Anyone?
 
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Frye? Frye?

I agree that the inspector is incorrect. If you have separate neutral and grounding conductors, as you do, there should be no bonding.

However, as an aside: the sub-panel, assuming seprate structures, must have a main disco if you have more than 6 breakers.
 
jeff43222 said:
Unfortunately, my brain isn't very quick with code references this late. Anyone? Anyone?
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possible code violations(in this case the inspector would be wrong)

250.6(A)
250.24(A)(5)
250.142
250.32(B)(1)

possible reason for inspectors decision(in this case he would be right)

250.32(B)(2)

Reviewing these sections may be of help to you (Mrat).

I would not be so quick to say the inspector is right or wrong with out more details.

Is there a possibility of neutral current flowing on parallel paths (metal raceway, cable, or EGC) ? If there is then the inspector is wrong.

On the contrary, if there are no parallel paths , the inspector would be correct in requiring a " neutral to case bond " at the seperate structure.

Hopefully , if the inspector is incorrect you could help to correct the problem.

There are shock/fire hazards that can result in improper bonding.


Ibew441dc
 
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I ran 1.5" PVC conduit from the 400 amp main to the pool subpanel. I used #4 CU for the power conductors. I used a #8 ground wire to the pool subpanel. The pool rebar bonds to every metal device around the pool and also over to the 4 pool pumps which in turn have a ground wire running through the flex with the 240V conductors back to the pool sub with the ground conductor tied to the ground bus. The pool sub does not have neutral/ground bonding. From the pool panel I ran a 1" PVC to the garage, a distance of about 10'. In that I ran #6 or #8 and sized the breaker accordingly. I also ran a #10 ground between subs. The Siemens subpanel allows you to physically tie the neutral bus to the box via a supplied green ground screw. By tightening the screw, you run through the neutral buss and into the metal box thus tying the two together. There is also a a ground wire running to the ufer ground, a 20' 5/8" piece of rebar embedded 3" up from the bottom of the concrete footing. Normally grounding the neutral is just not done on a subpanel and I was curious about why he wanted it done in this case.
 
ibew441dc said:
if there are no parallel paths , the inspector would be correct in requiring a " neutral to case bond " at the seperate structure.
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I thought this is merely an option, not a requirement, in order to omit a separate EGC.
 
I thought that the minimum disconnecting means for a detached structure would be 60A? Unless of course it was a 1 or 2 ckt installation. 225.39(D)

Tom

I agree that the Grounded to Grounding Conductor Bond is incorrect.
 
LarryFine said:
I thought this is merely an option, not a requirement, in order to omit a separate EGC.
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I agree. If the feeder contained an EGC it would be separated from the grounded conductor buss at the subpanel.
 
Davis9 said:
I thought that the minimum disconnecting means for a detached structure would be 60A? Unless of course it was a 1 or 2 ckt installation. 225.39(D)
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Agreed. A 60A Main Breaker should be installed in this 40A-fed subpanel to achieve compliance with this section. :)

I wholeheartedly agree with the above posters. Since you have installed an EGC with your feeder conductors, then the inspector is wrong. Leave the bonding screw in the trash can where it belongs.

Edit to add: Also, be sure your grounding electrodes are connected to the grounding bus in the panel, per 250.32(B)(1).
 
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Thanks for your input, I appreciate the brain power giving me something to chew on or at least another reason to whip out my glasses read the NEC sections and attempt to understand what sometimes takes ten reads before I get it and even thats not guranteed.
 
jeff43222 said:
I'm a little confused here. From your description, it sounds to me like the neutral and ground bars were bonded, which would be a problem in a subpanel. But you also seem to say that the subpanel failed because the neutral was not bonded.

The only place you bond the neutral to the ground is in the main panel. Neutrals and grounds are to be kept separate everywhere else downstream. If the inspector is telling you to connect the neutral and ground bars in a subpanel, he's wrong. Unfortunately, my brain isn't very quick with code references this late. Anyone? Anyone?
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I agree. The ground and neutral are only connected (bonded) in the main service panel. Not at the sub panel. I know this as I also failed an inspection a long time ago because I bonded the ground and Neutral at the sub panel.
 
You did put your grouds to a seperate ground bar that is mounted directly to the panel? I guess what I am asking is, there is some point where the incoming EGC and the footer ground wire hit the panel can itself, correct?
 
LarryFine said:
I thought this is merely an option, not a requirement, in order to omit a separate EGC.
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Not having all of the details can lead to many assumptions. I was pointing out different scenerios in my original post.

Though it is an option to run a seperate EGC (wire type, raceway,etc.), If you do not run an EGC you are definetly required to bond the grounded conductor to EGCs , GES , and GEC. I would recommend reviewing 2005 NEC , 250.32(B)(1)and(2).

If you do not bond in this case there will be no way to clear a fault on the feeder conductors.

ibew441dc
 
ibew441dc said:
If you do not run an EGC you are definetly required to bond the grounded conductor to EGCs , GES , and GEC.

If you do not bond in this case there will be no way to clear a fault on the feeder conductors.
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Absoloopy! However, there must be no other metallic pathway between structures to use this method.
 
JohnJ0906 said:
You did put your grouds to a seperate ground bar that is mounted directly to the panel? I guess what I am asking is, there is some point where the incoming EGC and the footer ground wire hit the panel can itself, correct?
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Yes John, all the ground wires including the ufer ground go to the separate ground bus which is screwed directly to the box. The neutral bus has insulators that keep it off the box. All my neutrals go to it. With Siemens subpanels, the green ground screw is part of the fixture. It is in the non bonded position when you buy it. You bond by screwing it down giving the neutral bus direct contact through the box. I now wonder if the inspecor did not see the ground wire coming from the pool subpanel. My past attempts to get in touch with him were nil.
 
Mrat, it would be a good idea to remove the screw completely, and put it in the "misc screws" bin in your van.

Someday, someone will follow behind you and say, "Look, a loose screw" and tighten it. Now, neutral current will start flowing along the EGC, regardless of how numb the screw-tightener is.

And all this discussion will have been for naught. :D
 
georgestolz said:
Mrat, it would be a good idea to remove the screw completely, and put it in the "misc screws" bin in your van.

Someday, someone will follow behind you and say, "Look, a loose screw" and tighten it. Now, neutral current will start flowing along the EGC, regardless of how numb the screw-tightener is.

And all this discussion will have been for naught. :D
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Thanks George. I would really like an explanation from the inspector on his logic. Your comment about the screw makes much sense. I just finished redoing my 100 amp subpanel and will redo my 200 amp meter/main shortly. The previous owner was a hack. The first thing I do when checking electrical panels is check all screws for tightness, especially the alu wired ones. I tightened a few on mine and can only guess what those not sure about the green ground screw would do. I would also wonder why they had the panel apart in the first place but thats another story. I really appreciate everyones input.
 
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