Equipment Bonding Jumper

[charlie b]

I don?t understand this beast. Can someone give me an example of where it may reside?

Here?s my problem: Consider a simple, single phase, branch circuit. I run one black wire from the breaker terminals and connect it to one side of the load. I run one white wire from the neutral bar and connect it to the other side of the load. I run one green wire from the ground bar and connect it to the case of the load. That green wire is one long wire. It does not have ?two or more portions,? this phrase being taken from the article 100 definition of ?bonding jumper, equipment.?

So when does an EGC have ?two or more portions??

This question comes from a disagreement regarding the total number of wires to be run from the secondary of a transformer (480-120/208) to the distribution panel it serves, the correct name to be given to each wire, and the correct method of sizing each wire. Let?s ignore the phase wires, and talk only about wires that have the letters ?g-r-o-u-n-d? or ?b-o-n-d? or that include the word ?jumper.? I know it matters whether the N-G connection happens at the transformer or at the panel. In the case under discussion, it happens at the transformer.

 

[charlie]

. . . So when does an EGC have ?two or more portions?? . .

The following is from the 2008 Edition of the NFPA NEC Handbook. Black is the NEC and the brown is from the commentary.

Bonding Jumper, Equipment. The connection between two or more portions of the equipment grounding conductor.

The use of equipment bonding jumpers ensures that the electrical continuity of an effective ground-fault current path is not compromised by an interruption in mechanical continuity, as is the case with metal conduits entering an open-bottom switchboard, or an interruption of electrical continuity resulting from loosely joined metal raceways, as is inherent to an expansion fitting intended to allow for movement in a metal conduit system. Equipment bonding jumpers are used to connect the grounding terminal of a receptacle to a metal box that in turn is grounded via an equipment grounding conductor in the form of a metal raceway system. Equipment bonding jumpers around expansion fittings for rigid metal conduit as required by 250.98 are shown in Exhibit 100.4 (below). Some expansion fittings for metal conduit have an internal bonding jumper that is integral to the fitting, eliminating the need for the external bonding jumpers shown in Exhibit 100.4.

Exhibit 100.4 Equipment bonding jumpers installed to maintain electrical continuity around conduit expansion fittings. (Courtesy of the International Association of Electrical Inspectors)

From what I understand, the equipment bonding jumper is to connect different parts of equipment grounding conductors together as shown in the above exhibit 100.4.

 

[dcspector]

Charlie b and Charlie,

Interesting you brought this up. I have been Inspecting a new building for the Coast Guard and the EC per specs used EMT expansion Couplings across the Expansion joints in the building. They pulled an EGC in the raceway but am I missing the bond jumper? Or is this internal Bond Jumper installed in the newer expansion couplings?

 

[iwire]

I would think if there is an internal EGC there would be no need for an external bonding jumper but if they wanted to use just the conduit as the EGC they would need to install a bonding jumper across the expansion joints unless they are specifically listed for grounding continuity.

I am impressed with Charlie's picture, those expansion joints show signs of regular movement.

 

[Pierre C Belarge]

A lot of the newer expansion couplings are coming with an integral bonding jumper.

Charlies picture is a good example of what the "other" Charlie is asking. A bonding jumper used around a pipe run is another example.

 

[Pierre C Belarge]

I would think if there is an internal EGC there would be no need for an external bonding jumper but if they wanted to use just the conduit as the EGC they would need to install a bonding jumper across the expansion joints unless they are specifically listed for grounding continuity.

I am impressed with Charlie's picture, those expansion joints show signs of regular movement.

There could be 2-sets of expansion couplings installed between the location where the EGC is terminated, such as at parking structures.

 

[erickench]

The definition of "Bonding Jumper, Equipment" in NEC 100 states:

The connection between two or more portions of the equipment grounding conductor.

According to NEC 250.118(2)&(3)&(4) rigid metal conduit, intermediate metal conduit and electrical metallic tubing qualify as equipment grounding conductors.
The two or more portions would be any one of these metal raceway types that become separated either by actual breakage or by a loose fitting.

 

[dcspector]

I would think if there is an internal EGC there would be no need for an external bonding jumper but if they wanted to use just the conduit as the EGC they would need to install a bonding jumper across the expansion joints unless they are specifically listed for grounding continuity.

I am impressed with Charlie's picture, those expansion joints show signs of regular movement.

Thanks Bob I had a brain lapse on that one for a minute. Yes EGC is installed. And yes great picture from Charlie.

 

[don_resqcapt19]

Charlie,
If you make the bond to the GEC at the transformer the conductor in question would be a "system bonding jumper". 250.30(A)(1)
If the GEC is connected at the first OCPD, then the conductor would be an "equipment bonding jumper". 250.30(A)(2)
As far as the number of wires between the transformer and the OCPD, the same number of conductors are required no matter where you place the bonding connection. In the case where the bonding is done at the OCPD, a metallic raceway may be able to serve as the "equipment bonding jumper", but not really sure about that.

 

[charlie]

The picture is from the 2008 Edition of the NFPA NEC Handbook and is the courtesy of the International Association of Electrical Inspectors. It is not my picture, I just copied it for the post and do not want to take credit for something that is not mine.

 

[RUWired]

In the case where the bonding is done at the OCPD, a metallic raceway may be able to serve as the "equipment bonding jumper", but not really sure about that.

Don, article 250.102 requires the equipment bonding jumper to be a wire, screw, bus, or other simular suitable conductor. Article 358.60 and 344.60 allow the raceways to be used as an equipment grounding conductor only.

Rick

 

[charlie b]

Thanks, and forgive my meager understanding. Let me be precise with my question.

From the center point of the transformer secondary, I run ?conductor number 1? to the ground bar that is on the wall of the room (this bar is ultimately connected to the grounding electrode system). From the center point of the transformer secondary, I run ?conductor number 2? to the case of the transformer. From the transformer to the distribution panel, I run three ungrounded conductors and one grounded conductor, along with ?conductor number 3.?

Questions:
1. Would I be right in calling ?conductor number 1? a ?grounding electrode conductor??
2. Would I be right in calling ?conductor number 2? a ?system bonding jumper??
3. Would I be right in declaring that the existence of ?conductors number 1 and 2? causes the N-G bonding to have taken place at the transformer?
4. Would I be right in saying that, at the transformer, I could connect ?conductor number 3? to either the center point of the transformer secondary, or to the transformer?s case, as they are essentially the same point now?
5. Would I be right is saying that, at the distribution panel, I connect ?conductor number 3? to the ground bar?
6. What is the correct name for ?conductor number 3??

My answer to question 6 is ?grounding electrode conductor.? The inspector?s answer was ?equipment bonding jumper.? The inspector?s answer would require that the conductor be larger than it would with my answer.

For the record, we have already replaced ?conductor number 3? with a larger wire, and the inspector is satisfied with that action. That all happened before I became aware of the issue. I just want to know if we needed to replace ?conductor number 3.?

 

[crossman gary]

On 1 through 5, I am saying you would be right.

On question 6, I am saying "equipment bonding jumper."

The equipment bonding jumper needs to be sized based on the cma of the secondary conductors. This is from 250.30(A)(2) as you already know.

The reason it needs to be sized for that is if an ungrounded conductor from the secondary goes to ground between the secondary and the panel main/disconnect, then the EBJ could be carrying the entire fault current. And we are relying only on the primary OCPD to clear the fault.

 

[crossman gary]

Also, 250.30(A)(3) says the GEC shall connect the grounded conductor to the electrode. Your conductor in #6 is not doing that. That wire is connecting the equipment enclosures/equipment grounds at the disconnect to the xfmr enclosure. The conductor in question #6 has nothing to do with the electrode, and this is because you connected the electrode to the transformer already.

That's how I see it.

 

[Smart $]

Questions:
1. Would I be right in calling “conductor number 1” a “grounding electrode conductor”?
2. Would I be right in calling “conductor number 2” a “system bonding jumper”?
3. Would I be right in declaring that the existence of “conductors number 1 and 2” causes the N-G bonding to have taken place at the transformer?
4. Would I be right in saying that, at the transformer, I could connect “conductor number 3” to either the center point of the transformer secondary, or to the transformer’s case, as they are essentially the same point now?
5. Would I be right is saying that, at the distribution panel, I connect “conductor number 3” to the ground bar?
6. What is the correct name for “conductor number 3”?

Answers:
1. Yes, a GEC.
2. Yes, an SBJ, but only if all other grounding conductors are connected to the case side of this jumper. Otherwise, no. It would then be an EGC.
3. Yes, assuming a yes answer to the previous question. If answer was no to previous question, we'd need better detailed description.
4. No and yes, respective to answer of Question 2.
5. Yes.
6. EGC.

 

[Smart $]

Don, article 250.102 requires the equipment bonding jumper to be a wire, screw, bus, or other simular suitable conductor. Article 358.60 and 344.60 allow the raceways to be used as an equipment grounding conductor only.

Rick

The grounding conductor described is an EGC.

 

[crossman gary]

In the past, I would have said that the conductor in question 6 was an EGC as Smart says. But someone pointed out recently that the EGC sections contain no requirement to use Table 250.66 or 12.5 % of the phase conductors, either at a service or at the secondary of the SDS. They only point to 250.122 for sizing. And we can't do that because typically there is no OCPD ahead of the "feeder" in question. If it is an EGC, then how is it sized?

so going on that alone, I say EBJ.

 

[Smart $]

In the past, I would have said that the conductor in question 6 was an EGC as Smart says. But someone pointed out recently that the EGC sections contain no requirement to use Table 250.66 or 12.5 % of the phase conductors, either at a service or at the secondary of the SDS. They only point to 250.122 for sizing. And we can't do that because typically there is no OCPD ahead of the "feeder" in question. If it is an EGC, then how is it sized?

so going on that alone, I say EBJ.

Ooops. My answer to charlie's Question 6 and response to RUWired is in error. You are correct. It is an EBJ, but not one which meets the definition. It is an EBJ as implied by section statements only... namely 250.30(A)(2), and thus 250.102(C).

 

[Smart $]

Don, article 250.102 requires the equipment bonding jumper to be a wire, screw, bus, or other simular suitable conductor. Article 358.60 and 344.60 allow the raceways to be used as an equipment grounding conductor only.

Rick

OK correction... an EBJ is required, but the question remains as to the definition of "similar suitable conductor".

IMO, if a screw is a suitable conductor, metal conduit certainly should be a suitable conductor :grin:

 

[Smart $]

Answers:
6. EGC.

Correction...

6. EBJ