Six Disconnect Rule

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charlie b

charlie b

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Hypothetical (but vaguely project related): Utility meter outside, wiring gutter immediately inside. Below gutter are six fused disconnect switches that feed separate branch circuit panels. Where do you put the neutral-to-ground bond(s)? I see three possibilities:
  1. There is just one, and it goes in the gutter.
  2. There are six, with one going in each disconnect switch.
  3. There are six, with one going in each downstream branch circuit panel.
 
#2 is the most accurate, but there are other correct answers. Also, and I admit I would have to think about and research this some more, it depends on what exactly you mean by "neutral to ground bond". Do you mean main bonding jumper? The meter and possibly the gutter would have a neutral ground bond, but it wouldn't be an MBJ.
 
charlie b said:
Hypothetical (but vaguely project related): Utility meter outside, wiring gutter immediately inside. Below gutter are six fused disconnect switches that feed separate branch circuit panels. Where do you put the neutral-to-ground bond(s)? I see three possibilities:
  1. There is just one, and it goes in the gutter.
  2. There are six, with one going in each disconnect switch.
  3. There are six, with one going in each downstream branch circuit panel.
Click to expand...

Couldn't we also terminate the GEC @ the weaterhead ?

~RJ~
 
charlie b said:
Hypothetical (but vaguely project related): Utility meter outside, wiring gutter immediately inside. Below gutter are six fused disconnect switches that feed separate branch circuit panels. Where do you put the neutral-to-ground bond(s)? I see three possibilities:
  1. There is just one, and it goes in the gutter.
  2. There are six, with one going in each disconnect switch.
  3. There are six, with one going in each downstream branch circuit panel.
Click to expand...
Greetings Charlie,

Since the rules in 250.28(B) state the following :

(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 to the grounded conductor within the enclosure for
each service disconnect in accordance with 250.28.

I would find it hard to not say option 2 was the proper choice. The gutter may be a choice for the GEC connection but not in this case for the MBJ connection.
 
MasterTheNEC said:
Greetings Charlie,

Since the rules in 250.28(B) state the following :

(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 to the grounded conductor within the enclosure for
each service disconnect in accordance with 250.28.

I would find it hard to not say option 2 was the proper choice. The gutter may be a choice for the GEC connection but not in this case for the MBJ connection.
Click to expand...

I'm with this guy.

I might be inclined to land the GEC upstream from the disconnects, just so I didn't have to do 6 taps of the main GEC to hit each disco.
 
electrofelon said:
#2 is the most accurate, but there are other correct answers. Also, and I admit I would have to think about and research this some more, it depends on what exactly you mean by "neutral to ground bond". Do you mean main bonding jumper? The meter and possibly the gutter would have a neutral ground bond, but it wouldn't be an MBJ.
Click to expand...
The meter and gutter will be bonded to the grounded conductor, there is no EGC until after the service disconnecting means.

romex jockey said:
Couldn't we also terminate the GEC @ the weaterhead ?

~RJ~
Click to expand...
You can, that is not what is being asked here. Main bonding jumper location is the question.
 
charlie b said:
Hypothetical (but vaguely project related): Utility meter outside, wiring gutter immediately inside. Below gutter are six fused disconnect switches that feed separate branch circuit panels. Where do you put the neutral-to-ground bond(s)? I see three possibilities:
  1. There is just one, and it goes in the gutter.
  2. There are six, with one going in each disconnect switch.
  3. There are six, with one going in each downstream branch circuit panel.
Click to expand...

I don't think item 3 bypassing the disconnects going in each downstream branch circuit panel would meet 250.24(B)
Item 1 would work if all 6 were in the same enclosure.

MasterTheNEC said:
Since the rules in 250.28(B) state the following :

(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 to the grounded conductor within the enclosure for
each service disconnect in accordance with 250.28.
Click to expand...

That reference is 250.24(B) not .28

Cheers
 
I respectfully disagree with option 1 since the gutter expressed can't meet all the functions of 250.24(B). Now, it the OP expresses that it can then possibly. However, at this point i see option 1 location as a good place for the GEC connection to the grounded conductor but thats about it in my opinion.

Sorry.....yes was referencing 250.24(B)...the .28 at the end of my quote lured me in...LOL

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
So what about 250.24B EX1?

wouldn't that allow for option #1?

ref HB exhibit 250.12

~RJ~
 
Last edited:
Paul,

Turn to page 178 in the '17 HB, check out exhibit 250.11

OR

Turn to page 180 in thew '17 HB , check out Exhibit 250.12

~RJ~
 
FWIW when we install a supply side connected PV system in San Antonio they direct us to use option #1. They require that we install a tap box between the meter and the customer's MDP and move the N-G bond from the MDP to the tap box.
 
Sorry I don't use handbooks...;)...It is their opinion and I frequently disagree with some of the employees of NFPA's.

With that said....its the language of the exception itself that creates the issue as a "gutter" itself as described in the OP hypothetical question is not applicable as asked and how written in the exception.

But I will go look later fella...family time today while i'm being stared at while tapping this in my phone...;)

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
ggunn said:
FWIW when we install a supply side connected PV system in San Antonio they direct us to use option #1. They require that we install a tap box between the meter and the customer's MDP and move the N-G bond from the MDP to the tap box.
Click to expand...
Well even In my posts I am trying to not give away the "expanding" use of the term Main Bonding Jumper that will be rolled out in the 2020 NEC. It will make the OP's question more interesting....but I digress on that....check out the First Draft of 2020...may find it interesting.

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
Nope.....i never use graphics from the Handbook at least I do not believe I do... Now, I own such books and they can help solidify an opinion but my graphics are either mine or IAEI graphics in seminars.



Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17
 
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