Neutrals On equipment Ground Bars.

[iwire]

In this thread Panel Rewire - Opinions, Please I had questions as to why there where neutrals on the ground bar, it turns out in this particular case there was a factory jumper between the Neutral bar and the ground bar so I was mistaken.

But some of the responses I got seemed to say that even with out the factory jumper it would be OK to land Neutrals on the equipment ground bar at a main panel as they are electrically the same.

This would mean you would be using the steel enclosure as a Neutral Conductor.

I feel this would be a violation of 110.5

110.5 Conductors.
Conductors normally used to carry current shall be of copper unless otherwise provided in this Code. Where the conductor material is not specified, the material and the sizes given in this Code shall apply to copper conductors. Where other materials are used, the size shall be changed accordingly.

310.14 provides for the use of Aluminum Conductor Material.

And 250.118 provides for the use of other materials for grounding conductors.

I do not believe there is anywhere in the code that provides for the use of a steel enclosure as a "conductor normally used to carry current".


IMO it would be wrong to do an installation that relied on the enclosure and the main bonding jumper whether it was a screw or a strap to carry current other than fault current.

I would like to hear any comments on this.

 

[a.wayne3@verizon.net]

Re: Neutrals On equipment Ground Bars.

Bob as long as the panel is the 1st (primary) Panel it is fine,neutrals and grounds may terminate on the same bar.Now if it is a sub panel well then, no they must be isolated....

 

[iwire]

Re: Neutrals On equipment Ground Bars.

Wayne I probably did not describe it well.

I am talking about a main panel that has both a neutral bar and a ground bar with out a jumper between them.

The neutral bar could have both neutrals and grounds.

But IMO the ground bar that is bolted / screwed to the enclosure should not have any Neutrals on it.

 

[big john]

Re: Neutrals On equipment Ground Bars.

Well, here's a question: How often would you be likely to run into a situation like that?

I don't know that I've ever been around an installation where there wasn't a bonding jumper or an isolated neutral bus.

I've heard about/seen pictures of panels with no jumper and only a bonding screw from the grounding bus to the panel can. In that case, I do agree that landing neutral conductors on the grounding bus would be a violation, as the enclosure isn't designed to be a current-carrying conductor under normal conditions.

Not only that, from the pictures I've seen, I'd be suspect of the ability of that bonding connection to safely handle large currents for any extended time.

-John

 

[iwire]

Re: Neutrals On equipment Ground Bars.

Originally posted by big john:
Well, here's a question: How often would you be likely to run into a situation like that?

I hope never, but this question has come up before on the electrical forums by inspectors that feel like I do.

IMO It is important to know the right way to do things even if the installation is not common.

 

[david]

Re: Neutrals On equipment Ground Bars.

Ok, I?ll walk close to the edge on this one. I have given this a lot of thought lately. This is very common in a service panel every time an equipment ground kit is added to a service panel. My personal opinion is you should have a bond sized according to 250.66 from the neutral bar to the equipment ground bar that you added. I can?t back this up with any code references. So I have to challenge my opinion.

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

I think it is key on understanding what needs bonded and how. By definition the equipment ground and grounded conductor need bonded. And according to 250.28 the equipment ground needs bonded to the enclosure. The material list given to bond these three together is given in 250.28 a wire, bus, screw, or similar suitable conductor. It would stand to reason that if a screw is allowed as a main bonding jumper between the neutral and the equipment ground in a service panel than that main bonding jumper would be sized to carry the current of the main in the panel.

This is where this area becomes gray for me. I personally would not want the neutrals landed on the equipment ground bar using the bond screw to carry current to the neutral bus. But I am not sure I can site a code violation here. I like your reference to 110.5 as to not allow the enclosure to carry the neutral current. I think this falls in line with the bond screw being green in color making it more in line to serve for equipment grounding purposes.

The forth thing needed bonded together would be the grounding electrode conductor and the neutral. It seems very clear that the grounding electrode conductor must land on the same bus as the neutral unless there is a main bonding jumper sized according to 250.66 between whatever bus or lug the grounding electrode lands on and the bus the neutral is landed on.

250.28 Main Bonding Jumper.

I have not had a clear reference to site for a violation when the equipment ground bus is used to land neutrals on in a service installation in the past I just asked that a bonding jumper be added to tie the equipment ground bus and the neutral buss together. So thank you for your reference to 110.5

 

[iwire]

Re: Neutrals On equipment Ground Bars.

Originally posted by david:
My personal opinion is you should have a bond sized according to 250.66 from the neutral bar to the equipment ground bar that you added.

David that would be my preference also.

For me this does not come up other than my own house, at work we bond at the switch gear and transformers so all panels are "sub panels" requiring isolated neutrals.

 

[bill addiss]

Re: Neutrals On equipment Ground Bars.

Bob,

I've got to admit I thought you were losing it when you first brought this up in the other thread. I see your point though now and as David points out this can happen when an equipment ground bar is added when someone runs out of terminals that were provided.

I seem to remember seeing stickers being supplied with the kits I've bought in the past which say something like "FOR EQUIPMENT GROUNDS ONLY" or something similar. I always thought of this applying to subpanel use, but maybe they did have the situation you describe in mind too?

Bill

 

[iwire]

Re: Neutrals On equipment Ground Bars.

Originally posted by bill addiss:
Bob,

I've got to admit I thought you were losing it when you first brought this up in the other thread.

Hey feel free to PM me when you think I am in the twilight zone.

I seem to be alone on my opinion here, so maybe I am mistaken and I can accept that.

 

[bill addiss]

Re: Neutrals On equipment Ground Bars.

I seem to be alone on my opinion here

Just hang on there a minute! ...

I saw the connection between the bars (other thread) and didn't understand before what your concern was. Let's see what we can dig up on this.

I've got a cover in front of me from a Murray 100 Amp Panelboard which clearly shows 2 Bars labelled differently. The diagram seems to show the only connection between the "Equipment Ground" Bar and the "Neutral" bar is when the jumper is used. This seems to be the situation under discussion.

The label discusses multiple combinations of conductors allowed for the "Equipment Ground" bar. Also at the end it says the following:

When used as Service Equipment, unused Neutral Bar Terminals may be used to terminate Equipment Grounding Wires in the combinations indicated for Equipment Ground Bar Terminals

It sure seems like Murray agrees with you.

Bill

[ October 01, 2003, 05:59 PM: Message edited by: bill addiss ]

 

[hurk27]

Re: Neutrals On equipment Ground Bars.

Let's reverse engineer this.
Why does every panel manufacture install a factory jumper between the two bars if the panel was allowed to carry the current?
I don't think they would if it wasn't required as it adds cost to the panel.specially if a screw could do the same thing.
so somewhere there is a requirement for this. we just need to find it.
It could be a UL requirement. and if it is, then we are required to follow it.

 

[frenchelectrican]

Re: Neutrals On equipment Ground Bars.

:roll:

 

[frenchelectrican]

Re: Neutrals On equipment Ground Bars.

opps : sorry i hit wrong key


anyway i wondering about the netural bus bar and grounding bus bar . i did look at 3 diffrent loadcenters and most have a grounding bar with screw in it but for neutral have both flat buss bar to grounding bar but one dont have it . and my pratice to keep netural and ground wire seprated to each bus bar . but the question there if no bus bar for both netural and grounding bus bar then can allow to use #6 wire between netural and grounding bus bar ?? bear in mind this is at main source not sub feed ok ??

and the second issuse is the ground fault. i wondering about the screw how long it will last over the time ??? i know steel screw with alumin bus bar is not really good combation to me but i will like hear your options


merci , marc

 

[bennie]

Re: Neutrals On equipment Ground Bars.

The green screw can be considered a bonding jumper only when metal conduit is the equipment ground conductor.

On a NM cable wiring method, the green screw is only bonding the can to ground.

 

[david]

Re: Neutrals On equipment Ground Bars.

Bennie

Do think the green screw is also the bond between the equipment ground and the neutral? It seems that this is all the Code requires as a main bonding jumper between the two. If so the green screw would serve as the effective fault- clearing path for the equipment ground.

 

[bennie]

Re: Neutrals On equipment Ground Bars.

David: No I don't think the screw meets the size required for a bonding jumper. The NEC appears to indicate otherwise.

I don't think the metal enclosure constitutes an equipment ground conductor.

 

[Guest]

Re: Neutrals On equipment Ground Bars.

I always believed the green bonding screw was to bond the panel to the buss-- not to bond one buss to another through the panel chassis-- nor to bond the buss to the panel. The screw is a method for the panel to be part of the bond, but not the source of the bond. Please correct me if I'm wrong-- as it's just been a long standing assumption that made sense. Personally, I would jumper a piece of large copper wire from buss to buss to bond them together as one unit.

 

[bill addiss]

Re: Neutrals On equipment Ground Bars.

I think I found a panelboard to match the cover I was looking at earlier and it does seem to have a flat bus that would also connect the two bars ("Equip Grnd" and "Neutral") when the jumper is used. See (left side) Murray Panel. Note that the bars are labelled differently by Murray.

2 different GE panelboards that I have, by comparison, come with 2 "Neutral" Terminal Bars and no Equipment Grounding Bars (they're optional). These have a connecting Bus between them and are bonded to the cabinet thru the Bonding Screw.

Bill

[ October 01, 2003, 11:27 PM: Message edited by: bill addiss ]

 

[david]

Re: Neutrals On equipment Ground Bars.

__________________________________________________
The screw is a method for the panel to be part of the bond, but not the source of the bond.
__________________________________________________

Wayne;

The screw is the main bonding jumper for the purpose of bonding the equipment ground to the enclosure. It also serves as the main bonding jumper for the neutral bond to the equipment ground. And if you add a grounding kit that is mounted, (bonded) to the enclosure it serves as the bond between the Neutral/equipment ground bus and the grounding kit bus. It is the main bonding jumper to ground the ground kit since the bond screw is the only link from the enclosure that the kit is bonded to and the grounding electrode that is tied to the neutral bus.

So I would say the main equipment bonding screw is the source of the bond. At least it is a code compliant main bonding jumper.

 

[hurk27]

Re: Neutrals On equipment Ground Bars.

David I have to agree with you as all the panel we use the bars are insulated from the cabinet and when there used as service equipment this bonding screw is the only thing that would keep the fault current from getting back to the service neutral and it will take the full amperage of the fault.
This is the GEC, EGC,to Ungrounded conductor, Main bonding jumper that is required in 250.24 (4)

But what I was trying to convey was I don't think the panel can be used as a normal current carrying conductor as Iwire has said. and one of my reasons for this belief is the fact that the manufactures install the jumper between the bars.