Neutrals and ground on the wrong bus.

[jaggedben]

If you can directly connect any EGC to the grounded conductor in the service disconnecting means enclosure, what is the purpose of the main bonding jumper and why would we need one?

To bond everything that's not directly connected.

By the way in your example panel the MBJ is not the tie bar between the two terminal bars. It is the 'bonding z strap'. Because that's what connects the isolated neutral to the enclosure and other non-current carrying parts.

 

[kwired]

If you can directly connect any EGC to the grounded conductor in the service disconnecting means enclosure, what is the purpose of the main bonding jumper and why would we need one?

The enclosure still needs bonded. Get gear that is suitable only for use as service equipment and the neutral bus is not isolated from the enclosure.

You can not use the enclosure/bonding screw as primary current path for the grounded conductor, AFAIK you could have multiple grounded conductor buses mounted directly to the enclosure (service or first disconnect of SDS applications) and connect grounded and EGC conductors to all of them - as long as there is a bonding jumper/bus between them and not relying on the enclosure for continuity of the grounded conductor.

On supply side of service disconnect we bond everything to the grounded conductor, what makes this a danger to do so at the service disconnect? I sort of think we should separate EGC from the grounded conductor at the source, and we mostly do with SDS's but that is a different discussion.

 

[gndrod]

bonding 'z' strap pic

bonding 'z' strap pic

To bond everything that's not directly connected.

By the way in your example panel the MBJ is not the tie bar between the two terminal bars. It is the 'bonding z strap'. Because that's what connects the isolated neutral to the enclosure and other non-current carrying parts.

Panel examples in post 3, post 40 and post 31 are shown with an unconnected panel bonding 'z' strap. The termination of the bonding 'z' strap only connects the panel enclosure for an EGC protection feature. The Main Neutral Bus is selected from one of the two isolated terminal bars to be connected to the incoming Neutral service conductor from the ac system power source. The MBJ would be the horizontal "tie bar" in this unique manufacturer's panel but must be disconnected for the 4-wire configuration. A 3-wire panel hookup would retain the MBJ as shown with the equipment enclosure bonded by the EGC bonding 'z' strap.

A 4-wire panel would also have the 'z' strap connected to the right terminal bar as configured. Using this particular brand panel configuration would need to have the utility ac system supply side grounded service conductor attached on the left terminal bar as the unbalanced 'Neutral' return. Refer to the post 40 that describes the way the BR Renovation type panel would be terminated differently between a 3-wire versus 4-wire system hookup.

 

[wwhitney]

An EGC terminal bus is, but a wire-type EGC is not considered a non-current-carrying metal part within the service disconnecting means enclosure per definition

I don't understand your objection to 250.142(A)(1) as allowing the practice of intermingling neutrals and EGCs within the enclosure of the service disconnecting means, as long as 200.2(B) is not violated. 250.24(A)(5) says "except as otherwise permitted in this article," and 250.142(A)(1) is in the article. Please clarify.

Cheers, Wayne

 

[Smart $]

I don't understand your objection to 250.142(A)(1) as allowing the practice of intermingling neutrals and EGCs within the enclosure of the service disconnecting means, as long as 200.2(B) is not violated. 250.24(A)(5) says "except as otherwise permitted in this article," and 250.142(A)(1) is in the article. Please clarify.

Cheers, Wayne

250.142(A)(1) does not include EGCs. It says non-current-carrying metal parts of equipment within the service disconnecting means enclosure... which is not the same as EGCs. EGCs bond non-current-carrying metal parts not within the service disconnecting means enclosure (and are not a non-current-carrying metal part themselves; see definition).

 

[wwhitney]

250.142(A)(1) does not say EGCs. It says non-current-carrying metal parts of equipment within the service disconnecting means enclosure... which is not the same as EGCs. EGCs bond non-current-carrying metal parts not within the service disconnecting means enclosure (and are not a non-current-carrying metal part themselves; see definition).

I believe earlier you indicated that an EGC terminal bar is a non-current-carrying metal part. EGCs may be landed there by (250.? Couldn't quickly find it). 250.142(A)(1) says that inside the enclosure of the service disconnecting means, the EGC terminal bar may be bonded by the neutral, so the neutrals can be landed there.

Alternatively, 250.142(A)(1) says the neutral may be bonded to the enclosure of the service disconnecting means, and of course EGCs may be landed there (by 250.? again). Hence they may be interconnected within the enclosure of the service disconnecting means.

Cheers, Wayne

 

[gndrod]

Manufacturer design trap

Manufacturer design trap

OK it's estimated that there's about 75 million single family homes in the United States and let's say 80% (60 million) have panels that are functionally identical to the one in the photo, it's your contention that all 60,000,000 are in violation because the neutrals and EGC's are intermingled on both sides of the panel which has two separate bus bars that the manufacturer connects together?

Hi Rob,
This question brings up how a panel design can trip up even the most experienced contractor. If the panel shown in post 3 is used in a 4-wire system, the right side terminal bar needs to be used for the grounded Neutral bar. The 2/0 lug on the left side terminal bar may require extra labor for 200 A cable termination when running a 4/0-4/0-4/0-2/0 feeder.

The 3-4/0 feeder Neutral conductor cannot be connected to the 2/0 lug in the example panels represented in this thread. The trap occurs when bonding an EGC 'z' strap that needs to be relocated for modification to the panel's left side terminal bar interface. A heads up caution on using BR panel configurations to avoid 'z' strap EGC violations for dwelling installations. By swapping the two terminal bar lugs is not an easy answer.

 

[Smart $]

I believe earlier you indicated that an EGC terminal bar is a non-current-carrying metal part. EGCs may be landed there by (250.? Couldn't quickly find it). 250.142(A)(1) says that inside the enclosure of the service disconnecting means, the EGC terminal bar may be bonded by the neutral, so the neutrals can be landed there.

Alternatively, 250.142(A)(1) says the neutral may be bonded to the enclosure of the service disconnecting means, and of course EGCs may be landed there (by 250.? again). Hence they may be interconnected within the enclosure of the service disconnecting means.

You, as many others, are ignoring 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 to the grounded conductor within the enclosure for each service disconnect in accordance with 250.28."

You cannot bypass the Main Bonding Jumper and connect EGCs directly to the grounded conductor.

 

[jaggedben]

You, as many others, are ignoring 250.24... You cannot bypass the Main Bonding Jumper and connect EGCs directly to the grounded conductor.

And yet in your example panel, if the tie bar is considered the MBJ, it is not an unspliced MBJ that bonds the enclosure. Hmmm.

I still think that nothing in 250.24 clearly contravenes 250.130 (A).

 

[jaggedben]

Panel examples in post 3, post 40 and post 31 are shown with an unconnected panel bonding 'z' strap. The termination of the bonding 'z' strap only connects the panel enclosure for an EGC protection feature. The Main Neutral Bus is selected from one of the two isolated terminal bars to be connected to the incoming Neutral service conductor from the ac system power source. The MBJ would be the horizontal "tie bar" in this unique manufacturer's panel but must be disconnected for the 4-wire configuration. A 3-wire panel hookup would retain the MBJ as shown with the equipment enclosure bonded by the EGC bonding 'z' strap.

A 4-wire panel would also have the 'z' strap connected to the right terminal bar as configured. Using this particular brand panel configuration would need to have the utility ac system supply side grounded service conductor attached on the left terminal bar as the unbalanced 'Neutral' return. Refer to the post 40 that describes the way the BR Renovation type panel would be terminated differently between a 3-wire versus 4-wire system hookup.

Without having a detailed manual for the panel I don't know why it wouldn't be an acceptable option, with a 4 wire hookup, to use both bars that come with the panel as neutral bars, add an additional equipment ground bar as needed, and leave the z-strap unconnected or even remove it.

 

[wwhitney]

You, as many others, are ignoring 250.24... You cannot bypass the Main Bonding Jumper and connect EGCs directly to the grounded conductor.

That argument would have merit if 250.24 required that the MBJ be the sole connection between the grounded conductor and the EGCs. But itt does not. So you can have an MBJ as required by 250.24, and have other such connections as allowed by 250.142(A)(1).

Cheers, Wayne

 

[Smart $]

That argument would have merit if 250.24 required that the MBJ be the sole connection between the grounded conductor and the EGCs. But itt does not. So you can have an MBJ as required by 250.24, and have other such connections as allowed by 250.142(A)(1).

Afraid not. You are reading those sections as either-or requirements. They are not. They are one and the other requirements. That is, they are separate requirements and both must be met.

Don't forget the title of 250.142(A) is "Supply-Side Equipment." Even if an EGC was a non-current-carrying metal part. you can't have an EGC on the supply-side of the service disconnecting means.

 

[kwired]

Afraid not. You are reading those sections as either-or requirements. They are not. They are one and the other requirements. That is, they are separate requirements and both must be met.

Don't forget the title of 250.142(A) is "Supply-Side Equipment." Even if an EGC was a non-current-carrying metal part. you can't have an EGC on the supply-side of the service disconnecting means.

Where is the line that separates supply side and load side of the service disconnecting means, and/or what do you call anything that may fall in between each side? Add to that the fact we typically do not disconnect the grounded conductor with the service disconnecting means.

 

[Smart $]

Where is the line that separates supply side and load side of the service disconnecting means, and/or what do you call anything that may fall in between each side? Add to that the fact we typically do not disconnect the grounded conductor with the service disconnecting means.

So when is there distance between a line? :huh:

IMO the line is drawn at the main bonding jumper. Everything before it is supply side and everything after it or on the end opposite its connection to the grounded supply-side conductor is the load side.

 

[kwired]

So when is there distance between a line? :huh:

IMO the line is drawn at the main bonding jumper. Everything before it is supply side and everything after it or on the end opposite its connection to the grounded supply-side conductor is the load side.

Now you have made me have to go read the sections you keep quoting

 

[gndrod]

Mfr compliance using OEM bus for all EGC terminations

Mfr compliance using OEM bus for all EGC terminations

Without having a detailed manual for the panel I don't know why it wouldn't be an acceptable option, with a 4 wire hookup, to use both bars that come with the panel as neutral bars, add an additional equipment ground bar as needed, and leave the z-strap unconnected or even remove it.

This is a good resolution if you have the compliant mfr's ground bus in the truck stock. Like you mention, having the install tech manual might help for an alternate option. An optional ground bus would be a rare economical solution for the good suggestion you give though. Tx, rbj

 

[wwhitney]

Afraid not. You are reading those sections as either-or requirements. They are not. They are one and the other requirements. That is, they are separate requirements and both must be met.

I don't understand how the above applies in any way to the logic I'm presenting. Let's start again at the beginning:

250.24(A)(5) says no connections between the grounded conductor and the EGCs except as permitted in Article 250, on the load side of the service disconnecting means.
250.24(B) says we need to make one connection between the grounded conductor and the EGCs/service disconnecting means enclosure, the Main Bonding Jumper.

If that's all there was in Article 250, I would agree with your position. But as jaggedben pointed out a while ago, we also have:

250.130(A) says that EGC connections at service equipment shall be made by bonding the EGC to the grounded conductor and grounding electrode conductor.

That section is more on point that the other sections I've sited.

So the following installation is compliant:

Main service panel with one or more interconnected terminal bars insulated from the case.
Land the grounded service conductor on the above terminal bar.
Install a Main Bonding Jumper from that terminal bar to the enclosure to satisfy 250.24(B).
Land any EGCs of the wire type on the same terminal bar, which meets 250.130(A), and hence 250.24(A)(5).

Now if 250.130(A) said that EGCs shall be bonded to the grounded service conductor "through the Main Bonding Jumper, such that removal of the Main Bonding Jumper shall leave the EGC unconnected to the grounded service conductor," then I would agree with your position.

But of course, 250.130(A) doesn't say that.

Cheers, Wayne

 

[Smart $]

I don't understand how the above applies in any way to the logic I'm presenting.

That's the crux of the problem. :happyyes:

Let's start again at the beginning:

Let's not. :happyno:

The logic is simple. Are all EGCs and the service disconnecting means enclosure connected to the grounded conductor through the MBJ? If yes, the installation is compliant. If no, the installation is not compliant. There are only a few conditions which are an exception to this logic, and none apply to the situation of this thread.

Have you seen that Febreze commercial which implies a condition known as nose blindness. What we have here is a case of Code interpretation blindness. Keep on tossing the logic around for all the relative sections. Do not forget to include the section titles. Eventually, you may get it.

 

[wwhitney]

The logic is simple. Are all EGCs and the service disconnecting means enclosure connected to the grounded conductor through the MBJ? If yes, the installation is compliant. If no, the installation is not compliant.

You have presented no section of Article 250 that requires that.

250.130(A) explicitly allows landing EGCs on the service panel neutral bar.

Cheers, Wayne

 

[Smart $]

... 250.130(A) explicitly allows landing EGCs on the service panel neutral bar.

Incorrect.

250.130(A) specifically states "The connection shall be made by bonding the equipment grounding conductor to the grounded service conductor and the grounding electrode conductor." The grounded service conductor ends at its termination to the grounded conductor terminal bus. The bus does not extend the service conductor.

You can land 4 types of conductors on the grounded conductor terminal bus:

1. grounded service conductor(s)
2. grounding electrode conductor(s)
3. main bonding jumper
4. load-side grounded conductors