Neutrals and ground on the wrong bus.

[jaggedben]

If the terminal bar is the MBJ, exactly how is it between the grounded conductors and the EGC/enclosure?

How is it NOT? :lol::huh:hmy::roll::?
(Also you keep adding that 's' that isn't in the code. It's the grounded service conductor only.)

BTW, I forgot to make the following comment earlier.

So do we get to selectively determine Code compliance based on whether an issue makes no difference to safety or functionality?

Simplest answer: yes. The code gives such authority to an AHJ in 90.4, at least with respect to safety (not so much functionality). Moreover, the code has a purpose which is described in 90.1. When interpreting code requirements it is correct and reasonable, in my opinion, to consider the purpose of the code in the course of interpretation. This of course does not give either AHJs or (especially) contractors license to willfully ignore whatever code section one wants. But neither does the code call for itself to be enforced to the nitpicky letter without regard to its purpose.

 

[jaggedben]

And just another followup about purpose...
The only reason I can think of for wanting the EGCs and neutrals to be on separate terminal bars in service equipment is to be able to conveniently unbond them. And the only reason I can think of for wanting to conveniently unbond them would be if one wanted to convert the service equipment to a subpanel (i.e. if inserting new service equipment upstream, perhaps to upgrade the service). And yet, 90.1(B) says this:

... Compliance [with the Code] and proper maintenance result in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.

That sure doesn't make it seem like the purpose of the MBJ requirements is supposed to be to make future modifications easier. I'm not saying that because I can't think of another reason, that no such reason exists. But as far as I've noticed none has been offered or explained in this thread.

 

[wwhitney]

There is no difference between ends of a line on a schematic, but there is for the ends of a real wire. The same is true of a terminal bus when you have to fit an MBJ between conductors and all the conductors are connected to the same terminal bus.

Wow, you seem to have a very unusual definition of between. A terminal bus is between any two conductors landed on it (in separate pressure connectors). Both electrically and physically.

Cheers, Wayne

 

[wwhitney]

P.S. 250.28(A) says "A main bonding jumper and a system bonding jumper shall be a wire, bus, screw, or similar suitable conductor." That certainly encompasses terminal bars.

Cheers, Wayne

 

[Smart $]

Wow, you seem to have a very unusual definition of between.

Here I am sitting on this end of the internet thinking the exact same thing about you. :lol:

I'll be back with more later...

 

[electrofelon]

Here I am sitting on this end of the internet thinking the exact same thing about you. :lol:

I'll be back with more later...

Is the Internet BETWEEN you and wwhitney? :lol:

 

[kwired]

Let's say you have a three-hole non-isolated neutral terminal bus, holes numbered 1-3, top to bottom. The grounded service conductor is connected to the top hole (#1).

You have one grounded circuit conductor (GCC) and one EGC. Put the EGC in hole #2 and the GCC in hole #3. If the MBJ must be between grounded conductors and EGCs, is there a violation here?

Same situation, maybe more holes/conductors in the bus - grounded service conductor in top hole, main bonding jumper is connected to center hole. Does this mean only grounded conductors are permitted in top half of bus and EGC's only in bottom half?

Is the Internet BETWEEN you and wwhitney? :lol:

And where is it bonded?

 

[infinity]

After 127 posts I think that the OP is sorry that he asked this seemingly simple question. :roll:

 

[jim dungar]

The only reason I can think of for wanting the EGCs and neutrals to be on separate terminal bars in service equipment is to be able to conveniently unbond them.

One of the most common reasons to unbound the neutrals and EGCs is during troubleshooting, particularly when looking for improper downstream N-G bonds.

 

[jim dungar]

A terminal bus is between any two conductors landed on it (in separate pressure connectors). Both electrically and physically.

I agree.
I have seen specifications for landing conductors in specific locations busbar (in one case, effectively all power circuit ground needed to be landed in the middle of the bar and all communication circuit grounds on one end, and all process circuit grounds on the other end). The designer of these connection requirements clearly consider that there is a 'between' on a busbar.

 

[jaggedben]

One of the most common reasons to unbound the neutrals and EGCs is during troubleshooting, particularly when looking for improper downstream N-G bonds.

I see. Nevertheless, if we agree that one is allowed to land neutrals and grounds on a single non-isolated terminal bar in a service equipment enclosure, the consideration you raise has no bearing on where they are landed.

 

[jim dungar]

... we agree that one is allowed to land neutrals and grounds on a single non-isolated terminal bar in a service equipment enclosure, the consideration you raise has no bearing on where they are landed.

:thumbsup::thumbsup:

 

[wwhitney]

The same is true of a terminal bus when you have to fit an MBJ between conductors and all the conductors are connected to the same terminal bus.

To followup on the "between" discussion, I changed the highlighting in the text I quoted from you.

The Main Bonding Jumper definition refers to the "connection between" the grounded circuit conductor and the EGC. You seem to be conflating "connection between" with "fit between", but the word between has different meanings in those two contexts. For example, a wire nut provides a "connection between" two conductors, but it does not "fit between" the conductors.

There is no language in the NEC I am aware of that requires a Main Bonding Jumper to "fit between" the grounded circuit conductor and the EGC. If wirenuts were listed under 250.28(A), then a giant wirenut could be the Main Bonding Jumper.

Cheers, Wayne

 

[Smart $]

Same situation, maybe more holes/conductors in the bus - grounded service conductor in top hole, main bonding jumper is connected to center hole. Does this mean only grounded conductors are permitted in top half of bus and EGC's only in bottom half?

Here's the way I view the default NEC panelboard grounding requiremen



The way I see it, the GC/EGC terminal bus in a service-only panelboard is already a special case consideration not conforming to the "ideal" NEC system grounding. The manufacturers and UL give no credence to where the jumper screw(s) are located. Those screws are not the MBJ if you connect EGC's to that terminal bus. They would be if you installed a separate EGTB bonded only through the enclosure (i.e. no additional bonding wire or busbar).

I've already went on record stating the whole bus is the MBJ, and I've been attempting to express why I believe as a best workmanship practice we should keep GCC's and EGC's "arranged". But, I see y'all are forming a collective against my belief, so as much as I know how to quit while I'm ahead, I certainly know how to quit when I'm outnumbered on a point that is trivial if not totally meaningless in the grand picture of things.

 

[kwired]

Here's the way I view the default NEC panelboard grounding requiremen

View attachment 16354

The way I see it, the GC/EGC terminal bus in a service-only panelboard is already a special case consideration not conforming to the "ideal" NEC system grounding. The manufacturers and UL give no credence to where the jumper screw(s) are located. Those screws are not the MBJ if you connect EGC's to that terminal bus. They would be if you installed a separate EGTB bonded only through the enclosure (i.e. no additional bonding wire or busbar).

I've already went on record stating the whole bus is the MBJ, and I've been attempting to express why I believe as a best workmanship practice we should keep GCC's and EGC's "arranged". But, I see y'all are forming a collective against my belief, so as much as I know how to quit while I'm ahead, I certainly know how to quit when I'm outnumbered on a point that is trivial if not totally meaningless in the grand picture of things.

But there sort of isn't a one size fits all that is always practical either. If the busbar is directly mounted to the cabinet you are saying it is or can be the grounded conductor bus, the EGC bus and the MBJ all in same component? Put same bus on insulators and you need three separate components for each though?

I see the logic there but also believe it isn't necessary to consider either one of the situations any differently, IMO the grounded service conductor, MBJ, an EGC are electrically all the same point at the service disconnect enclosure. We can not rely on the enclosure for continuity of the grounded conductor, that is specifically mentioned in 200.2, but we can add more conductor, bus bar, etc. to additional sections of grounded conductor terminations, and if it is part of the service disconnecting means it usually is considered one assembly and the MBJ could attach anywhere to this one assembly.

 

[Smart $]

But there sort of isn't a one size fits all that is always practical either. If the busbar is directly mounted to the cabinet you are saying it is or can be the grounded conductor bus, the EGC bus and the MBJ all in same component? Put same bus on insulators and you need three separate components for each though?

I see the logic there but also believe it isn't necessary to consider either one of the situations any differently, IMO the grounded service conductor, MBJ, an EGC are electrically all the same point at the service disconnect enclosure. We can not rely on the enclosure for continuity of the grounded conductor, that is specifically mentioned in 200.2, but we can add more conductor, bus bar, etc. to additional sections of grounded conductor terminations, and if it is part of the service disconnecting means it usually is considered one assembly and the MBJ could attach anywhere to this one assembly.

Everyone keeps (conveniently) forgetting 250.24(A)(5) says a grounded conductor shall not be connected to an equipment grounding conductor on the load side of the service disconnecting means. If we had a simple disconnecting means, i.e. not a service panelboard, there'd be no question as to whether the grounded conductor was connected to an equipment grounding conductor because the MBJ would be obvious... though the concept is stretched even on separate disconnects. Quite simply, the Code only permits load-side grounded conductor(s) to be connected to an EGC through the MBJ. We all know these are conductors are electrically the same "conductor", so we stretch the rule... but Code gives these conductors specific names and specific end purposes to differentiate them from one another. No one has offered any Code section up that specifically repeals the requirements named. All I keep hearing is they are all connected. No sheet, Sherlock.

 

[jaggedben]

I've already went on record stating the whole bus is the MBJ, and I've been attempting to express why I believe as a best workmanship practice we should keep GCC's and EGC's "arranged". But, I see y'all are forming a collective against my belief, so as much as I know how to quit while I'm ahead, I certainly know how to quit when I'm outnumbered on a point that is trivial if not totally meaningless in the grand picture of things.

Ok, well said. I wouldn't be arguing the point if it were just about what's a better workmanship practice.

Everyone keeps (conveniently) forgetting 250.24(A)(5) says a grounded conductor shall not be connected to an equipment grounding conductor on the load side of the service disconnecting means. If we had a simple disconnecting means, i.e. not a service panelboard, there'd be no question as to whether the grounded conductor was connected to an equipment grounding conductor because the MBJ would be obvious... though the concept is stretched even on separate disconnects. Quite simply, the Code only permits load-side grounded conductor(s) to be connected to an EGC through the MBJ. ...

My point of view is that if it's a non-switched conductor in the service disconnecting means enclosure, it's not load side of anything until it leaves the enclosure.

 

[Smart $]

...
My point of view is that if it's a non-switched conductor in the service disconnecting means enclosure, it's not load side of anything until it leaves the enclosure.

So the ungrounded branch circuit conductors in the enclosure are still line-side conductors? :lol:

It's amazing what people will say to have it their way.

 

[Smart $]

But there sort of isn't a one size fits all that is always practical either. If the busbar is directly mounted to the cabinet you are saying it is or can be the grounded conductor bus, the EGC bus and the MBJ all in same component? Put same bus on insulators and you need three separate components for each though?

I see the logic there but also believe it isn't necessary to consider either one of the situations any differently, IMO the grounded service conductor, MBJ, an EGC are electrically all the same point at the service disconnect enclosure. We can not rely on the enclosure for continuity of the grounded conductor, that is specifically mentioned in 200.2, but we can add more conductor, bus bar, etc. to additional sections of grounded conductor terminations, and if it is part of the service disconnecting means it usually is considered one assembly and the MBJ could attach anywhere to this one assembly.

That's where 250.130(A) comes in. It requires EGC connections be made to the grounded service conductor. Once again, if we take this literally, the grounded service conductor ends at its termination to the terminal bus. It is only by stretching the meanings of NEC terminology that we bond to the grounded service conductor using the grounded conductor terminal bus. Note Code specifically permits connection of a GEC using this bus. Where's the specific permission allowing us to use this bus for EGC connections?

 

[Smart $]

...
My point of view is that if it's a non-switched conductor in the service disconnecting means enclosure, it's not load side of anything until it leaves the enclosure.

BTW, I realized after I posted my last reply you said non-switched. Point is, as far as the circuit goes, grounded branch circuit conductors are technically switched within the enclosure... just on the ungrounded side of the circuit.