Need Code Reference for Seperate Neutrals and Grounds on a MDP

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innersurffer

innersurffer

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I have a situation in that a 1600 amp MDP was originally bonded with a bonding jumper in the first section ( where the bonding jumper from the factory was installed ) to comply with the bonding the neutral and the ground as the first means of disconnect. A new ATS has been put in front (as far as feeding) this MDP and is now the first means of disconnect and as such, has the bonding jumper in it and we removed the bonding jumper from the MDP. Unfortunatly, the other sections of the MDP were not properly installed (as far as seperating the neutrals and grounds to their respective bars) and are not properly serperated. I believe, either in the original MDP installation or in the addition of panels over the years, the grounds and neutrals were not properly landed to their respective bars and have now become a code issue with this new ATS installation. Can someone give me a code reference that the grounds and neutrals should have been seperated in the original installation?
 
augie47

augie47

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I;m confident it did. From your post, I would think the issue arose when the ATS was added.
 
augie47

augie47

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Hate to second guess when I've not seen, but 250.28, especially (D)(1) would seem to allow for multiple jumpers. In the event of large services, you might need multiple jumpers if you are going to meet the 12-1/2% rule.
 
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skeshesh

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Hate to second guess when I've not seen, but 250.28, especially (D)(1) would seem to allow for multiple jumpers. In the event of large services, you might need multiple jumpers if you are going to meet the 12-1/2% rule.
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I don't think that's true. Take a look at 250.24(B) as well as Exception No. 1 under the same section, which allows only for one unspliced main bonding jumper even if there's multiple disco's in a single assembly.
 
innersurffer

innersurffer

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St Petersburg (Have lived in Lakeland, Miami, Ft L
The code you are refering to says:

"250.24 (B) Main Bonding Jumper. For a grounded system, an unspliced main bonding jumper shall be used to connect the equipment grounding conductor(s) and the service-disconnect enclosure for each service disconnect in accordance with 250.28

Exception No. 1: Where more than one service disconnecting means is located in an assembly listed for use as service equipment, an unspliced main bonding jumper shall bond the grounded conductor(s) to the assembly enclosure. "

The 2008 NEC Handbook goes on to comment about this by saying:

"Where multiple service disonnnecting means are part of an assembly listed as service equipment, all grounded service conductors are required to be run to and bonded to the assembly. However, only one section of the assembly is required to have the main bonding jumper connection."

I'm not sure this says that you can't add more bonding jumpers, but that by code, only one is required. I'm not sure if the inspector that red tagged this installation years ago may have interpeted this as mandatory. (Meaning that their shall be only on main bonding jumper.) Any other comments or NEC references?
 
P

Power Tech

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Lebec, California
innersurffer said:
The code you are refering to says:

"250.24 (B) Main Bonding Jumper. For a grounded system, an unspliced main bonding jumper shall be used to connect the equipment grounding conductor(s) and the service-disconnect enclosure for each service disconnect in accordance with 250.28

Exception No. 1: Where more than one service disconnecting means is located in an assembly listed for use as service equipment, an unspliced main bonding jumper shall bond the grounded conductor(s) to the assembly enclosure. "

The 2008 NEC Handbook goes on to comment about this by saying:

"Where multiple service disonnnecting means are part of an assembly listed as service equipment, all grounded service conductors are required to be run to and bonded to the assembly. However, only one section of the assembly is required to have the main bonding jumper connection."

I'm not sure this says that you can't add more bonding jumpers, but that by code, only one is required. I'm not sure if the inspector that red tagged this installation years ago may have interpeted this as mandatory. (Meaning that their shall be only on main bonding jumper.) Any other comments or NEC references?
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Don't be shy, go into the BD, bring the code book and ask him what code you violated and why.

That's his job.

The infraction (with code #) and explanation should have been on the correction notice.
 
innersurffer

innersurffer

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St Petersburg (Have lived in Lakeland, Miami, Ft L
Good Points any other insights for this situation?

Good Points any other insights for this situation?

Again, I know it's different for different situations. The question is in relation to a 5 section MDP, with a bonding jumper in the first section, and another (added by another installer), in another section. The first bonding jumper for this gear exceeds the 12 1/2% rule requirements and satisfys the bonding requirements for this 1600 amp gear. Most MDP's that I've installed are set up to have a main dissconnect section (where the bonding jumper takes place) and all subsequent section locked together as one. Their usually is multiple neutrals and grounds feeding out of the equipment to other locations, but only one bonding jumper seems to be the norm. I just wanted to know if it was required by code, for the bonding jumper to be in only one section of this gear (usually the utility entrance area) and that the grounds and the neutrals be seperated to their respective buss bars by code. Any other insights would be appreciated.
 
augie47

augie47

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skeshesh said:
I don't think that's true. Take a look at 250.24(B) as well as Exception No. 1 under the same section, which allows only for one unspliced main bonding jumper even if there's multiple disco's in a single assembly.
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You may be correct, 250.24 refers to "jumper" but refers you to 250.28 for sizing where it uses the terms "JumperS".
I note that on certain service equipment sized over 200 amps they supply two of the "jumpers" to connect the neutral bar to the can (Cutler-Hammer brand as I recall).
It would be simpler to assure proper sizing to install a single jumper and we may be in an AHJ judgment situation. Inspecting, I would prefer one, but if you showed me you met the cross sectional area requirement I would tend to accept it.

In the scenerio Ineersuffer notes in Post 14, I guess one could agrue that the first section with in the MDP was the service section and any bonding in the other sections might constitute a violation of 250.24(A)(5)
 
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skeshesh

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Location
Los Angeles, Ca
Bonding

Bonding

I'm not sure this says that you can't add more bonding jumpers, but that by code, only one is required.
Click to expand...

Exception No. 1: Where more than one service disconnecting means is located in an assembly listed for use as service equipment, an unspliced main bonding jumper shall bond the grounded conductor(s) to the assembly enclosure.
Click to expand...

I've always had pretty high scores in English (strangely since most of my other engineering buddies hated it!), but the way I read it is the use of "an" is equivalent to writing "one". I don't see why you'd take it to mean "at least one" is required.

You may be correct, 250.24 refers to "jumper" but refers you to 250.28 for sizing where it uses the terms "JumperS".
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Yea I was thinkin about that too, but I figured the use of plural is refering to more than one Jumper in the same system, which is clearly allowed in case of multiple buildings/multiple service disconnects. Your comments abount a possible violation of 250.24(A)(5) does seem to make sense, especially comparing it to the expection no. 1 quoted above, which would seem to allow for a multi-section distribution equipment to have only one section bonded.
 
innersurffer

innersurffer

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Location
St Petersburg (Have lived in Lakeland, Miami, Ft L
Great Answers and Insight

Great Answers and Insight

You can see with the words "jumpers" vs "jumper" and the word "an" meaning one, this can get interpreted in various ways. I also like how the inferences of the separate sections of the MDP being brought to light. I appreciate everyone's insight to help me get a clearer view of this situation. Thanks to everyone.
 
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