Six Disconnect Rule

[MasterTheNEC]

Not here to question your install. I am in this thread to answer the OP and meeting 250.24(B) can't be achieved as the OP is presented...wireway or junction box.

Your install is not my concern as you are entitled to your opinion and design, i have no right to place judging on your work and I would not do that. I am purely discussing the question and about it not meeting 250.24(B) with regards to the gutter, wireway or junction box.

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

 

[jaggedben]

...

Let me ask this, what in theory is the dif between an SSBJ and an MBJ , considering the predominant TN−C−S earthing system we have ?

...

In theory the difference is that until you get to the MBJ you only have TN-C instead of TN-C-S. If you lift the MBJ then all down stream EGCs may be ungrounded. Lifting an SSBJ just unbonds the particular thing(s) it's bonding.

 

[kwired]

well you're free to question my install Paul, i'm far from infallable , in fact i already see a few no-no's (it's over a decade old)

I can tell you that, if i didn't bond the serv rated gutter, my ahj would not have passed it (it follows the HB pix)

Let me ask this, what in theory is the dif between an SSBJ and an MBJ , considering the predominant TN−C−S earthing system we have ?

Fwiw, what you see is a 3ph open delta w/high leg, pedestal is maybe 15' from serving poco pole

~RJ~

This:

Who is missing what here? I see labels "main bonding jumper" in each service disconnect enclosure and labels "supply side bonding jumper" on all the other bonding jumpers .

From art 100:

Bonding Jumper, Main.
The connection between the grounded circuit conductor and the equipment grounding conductor at the service.

There is no equipment grounding conductor until you are past the service disconnecting means, all the raceways and enclosured ahead of the service disconnecting means don't have an EGC, they are just bonded to the grounded conductor, therefore the MBJ has to be at the service disconnecting means as there is no other point where you transition from grounded conductor to EGC.

And this

In theory the difference is that until you get to the MBJ you only have TN-C instead of TN-C-S. If you lift the MBJ then all down stream EGCs may be ungrounded. Lifting an SSBJ just unbonds the particular thing(s) it's bonding.

 

[ggunn]

We know from your previous posts that those Texas AHJs you work with lack either the motivation or the ability to conform with the NEC.

Ours is not to reason why, ours but to do what they say and pass inspection. Apologies to Alfred Lord Tennyson.

 

[charlie b]

I didn't mean to start a war on this one, but thanks for the input. Yes, I was referring to the main bonding jumper.

Attached is the one line that brought this issue to mind. I am not certain of the client's desired degree of confidentiality, so I blanked off most of the text.

It is an existing installation, likely decades old. My office is doing an independent review of the (minor) revisions another office is designing for this facility. There are several things I don't like about the existing design, and I wanted to get some other opinions before I submit my comments.

 

[MasterTheNEC]

I didn't mean to start a war on this one, but thanks for the input. Yes, I was referring to the main bonding jumper.

Attached is the one line that brought this issue to mind. I am not certain of the client's desired degree of confidentiality, so I blanked off most of the text.

It is an existing installation, likely decades old. My office is doing an independent review of the (minor) revisions another office is designing for this facility. There are several things I don't like about the existing design, and I wanted to get some other opinions before I submit my comments.

No war....good conversation my friend.

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

 

[Adamjamma]

Personally, I thank you for this question as it is helping me learn a lot more than the fifteen lines in the chapter on bonding and grounding in my text book did on service entrances. Thanks

 

[tortuga]

Personally, I thank you for this question as it is helping me learn a lot more than the fifteen lines in the chapter on bonding and grounding in my text book did on service entrances. Thanks

Ditto I enjoy reading these real world scenarios. It was helpful to see the 1 line Charlie uploaded.

 

[romex jockey]

I didn't mean to start a war on this one, but thanks for the input. Yes, I was referring to the main bonding jumper.

Attached is the one line that brought this issue to mind. I am not certain of the client's desired degree of confidentiality, so I blanked off most of the text.

It is an existing installation, likely decades old. My office is doing an independent review of the (minor) revisions another office is designing for this facility. There are several things I don't like about the existing design, and I wanted to get some other opinions before I submit my comments.

I see a GEC, where is the MBJ?

~RJ~

 

[charlie b]

I see a GEC, where is the MBJ?

That's my issue with this design. It's in the switchboard, and there are two other components between that switchboard and the main service disconnect. To make matters potentially worse, the main service disconnect and the switchboard are in one room, and the transfer switch and fuse "thingy" (don't ask what that really is) are in another room.

There are two places that grounding electrodes are connected to the electrical system. Whether there is an MBJ in the "terminal cabinet" is unknown to me. If there is, then the second MBJ inside the downstream switchboard would be a violation.

 

[jaggedben]

That's my issue with this design. It's in the switchboard, and there are two other components between that switchboard and the main service disconnect. To make matters potentially worse, the main service disconnect and the switchboard are in one room, and the transfer switch and fuse "thingy" (don't ask what that really is) are in another room.

There are two places that grounding electrodes are connected to the electrical system. Whether there is an MBJ in the "terminal cabinet" is unknown to me. If there is, then the second MBJ inside the downstream switchboard would be a violation.

Yup. :thumbsup:

To go back to your original post, option (3) is definitely not allowed.

Part of what's bothersome about the schematic you posted is that it displays no consistency either.

 

[romex jockey]

That's my issue with this design. It's in the switchboard, and there are two other components between that switchboard and the main service disconnect. To make matters potentially worse, the main service disconnect and the switchboard are in one room, and the transfer switch and fuse "thingy" (don't ask what that really is) are in another room.

There are two places that grounding electrodes are connected to the electrical system. Whether there is an MBJ in the "terminal cabinet" is unknown to me. If there is, then the second MBJ inside the downstream switchboard would be a violation.

It would appear the disco's under the 3R term cab all tapped off the service entrance in it?

Would that be correct?

~RJ~

 

[nickelec]

Something like this?

Sent from my SM-G950U using Tapatalk