2005 NEC Handbook Exhibit 250.13

[infinity]

Has anyone looked at the illustration (Exhibit 250.13) for Article 250.30? IMO the illustration labeled Exhibit 250.13 is incorrect. It seems that the terms "Equipment bonding jumper and System bonding jumper" are switched. Or am I reading this incorrectly?

 

[barbeer]

I understand what you are saying, but I think it is written correctly.

 

[infinity]

I understand what you are saying, but I think it is written correctly.

I have Mike Holt's Grounding vs. Bonding book and he has the two terms the opposite of the NECH. After reading 250.30(A)(1) & (2) I agree with Mike and feel that the NECH is incorrect.

 

[tallguy]

Point of interest... NECH 250.13 came up in the 2002 code cycle. Doesn't appear that the issue of possibly mis-labelled jumpers was broached.

 

[chris kennedy]

Has anyone looked at the illustration (Exhibit 250.13) for Article 250.30? IMO the illustration labeled Exhibit 250.13 is incorrect. It seems that the terms "Equipment bonding jumper and System bonding jumper" are switched. Or am I reading this incorrectly?

IMO the term System bonding jumper is used because although it looks like an EGC it is sized as per 250.28(D). This sends you to 250.66. But you already know that because you have the Handbook.:grin:

 

[infinity]

Here is Mike's illustration from his G v.B book,

The illustration in the NECH is calling this conductor an equipment bonding conductor not the system bonding jumper, which I believe is incorrect.

 

[JohnJ0906]

I think the NECHB diagram is not very clear. However, I'm not sure that it is mislabeled.

 

[infinity]

I think the NECHB diagram is not very clear. However, I'm not sure that it is mislabeled.

The NECH exhibit 250.13 (p.199) clearly shows the equipment bonding jumper going from the neutral to the case within the transformer. Mike Holt's illustration clearly shows the exact same connection but calls it the system bonding jumper. One of them is has to be wrong.

 

[JohnJ0906]

In the NECHB, I see a wire going from the EGCs to the system neutral. It is labeled "System Bonding Jumper"

The same wire in Mike's diagram is not labeled.

The only difference in the drawings that I see is that the GEC in the NECHB lands on the neutral bar, and in Mike's it lands on the Transformer case.

(Mike's diagram) Should the conductor that runs from panel EGC bar to X0 land with the GEC at the xfmr case?

 

[JohnJ0906]

The NECH exhibit 250.13 (p.199) clearly shows the equipment bonding jumper going from the neutral to the case within the transformer. Mike Holt's illustration clearly shows the exact same connection but calls it the system bonding jumper. One of them is has to be wrong.

Well, I'm not sure I know which one is right!

I know you have gotten me confused, though. :grin:

 

[mdshunk]

They're both bonding jumpers. :roll:

 

[JohnJ0906]

I think both are correct.

NECHB - The EBJ is bonding the xfmr case - and case only - to X0. The SBJ connects X0 to the EGCs. I think this is correct. However this is more of a 250.96(A) bond than a 230(A)(2) bond. :roll:

Mike's - The SBJ is bonding case AND GEC to X0. Also correct.

JMO

 

[jwelectric]

They both show the exact same thing.

The system bonding jumper is the same thing as the main bonding jumper in a main.

In both the system bonding jumper connects the grounding terminal to the neutral inside the transformer.

 

[Pierre C Belarge]

This is exhibit 250.14 in the NEHB. This is not the one that Trevor is discussing
Exhibit 250.13 in the NEHB is not clear, and as Trevor believes it is incorrect, so do I. Read the definition of Bonding Jumper, System in Art 100 and one can clearly see that the Conductor identified as System bonding jumper is the EGC or EBG, not the system bonding jumper. Since the GEC is terminated in the separately derived system (Transformer) The conductor that is identified in Exhibit 250.13 as the EBC should in my opinion be labeled as the System Bonding Jumper.

 

[infinity]

This is exhibit 250.14 in the NEHB. This is not the one that Trevor is discussing
Exhibit 250.13 in the NEHB is not clear, and as Trevor believes it is incorrect, so do I. Read the definition of Bonding Jumper, System in Art 100 and one can clearly see that the Conductor identified as System bonding jumper is the EGC or EBG, not the system bonding jumper. Since the GEC is terminated in the separately derived system (Transformer) The conductor that is identified in Exhibit 250.13 as the EBC should in my opinion be labeled as the System Bonding Jumper.

Yes Pierre,
I was referring to Exhibit 250.13 not 250.14. When you consider the definitions of system bonding jumper and equipment bonding jumper in 250.30(A)(1) and (2) the illustration (250.13) is incorrect. I don't have the NECH on CD or I would post exhibit 250.13.

 

[sicurezza elettrica]

Nech

Nech

Did anyone call or ask the Editors of the NECH at NFPA if there are any edits on this?

NFPA

I believe this image has been in this book for many years.

 

[jwelectric]

This is exhibit 250.14 in the NEHB. This is not the one that Trevor is discussing
Exhibit 250.13 in the NEHB is not clear, and as Trevor believes it is incorrect, so do I. Read the definition of Bonding Jumper, System in Art 100 and one can clearly see that the Conductor identified as System bonding jumper is the EGC or EBG, not the system bonding jumper. Since the GEC is terminated in the separately derived system (Transformer) The conductor that is identified in Exhibit 250.13 as the EBC should in my opinion be labeled as the System Bonding Jumper.

Sorry I did the wrong one so here is the right one. I can?t see any difference between the three of them, the one Mike Holt?s and the other two from the Handbook.

In all three pictures the System Bonding Jumper is bonding the Grounded (Neutral) to the Equipment Grounding Terminal. The difference between the two in the hand book is one is bonding in the transformer and the other is in the panel.

 

[radiopet]

The determination of which " Bonding Jumper " is the system bonding jumper depends on where the GEC is terminated to the GE....

And this is for a SINGLE SDS.....either at the source or the first disconnection means ( Enclosure ).

 

[barbeer]

Sorry I did the wrong one so here is the right one. I can?t see any difference between the three of them, the one Mike Holt?s and the other two from the Handbook.

In all three pictures the System Bonding Jumper is bonding the Grounded (Neutral) to the Equipment Grounding Terminal. The difference between the two in the hand book is one is bonding in the transformer and the other is in the panel.

I was starting to think I was losing it as This^^ is my pic.

I agree that this is all very confusing and herein lies the problem with the NEC. Semantics? I agree with the "equipment bonding jumper" label in the xfmr, not with the "system bonding jumper" in the panel.....EGC?!

 

[jwelectric]

I have found over the past few years that a lot of electricians and inspectors misunderstand just what the job of the Main/System bonding jumper is and just where it can be found in a panel.

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

Bonding Jumper, System. The connection between the grounded circuit conductor and the equipment grounding conductor at?..

I left off the last couple of words in each definition above so the actual purpose of the Jumper could be seen easier.

The Main Bonding Jumper makes this connection at the service and the System Bonding Jumper does it at a separately derived system.

In both cases the purpose is to establish a low impedance connection between the conductor that connects all non-current carrying metal parts to earth (the equipment grounding conductor) and the grounded (neutral) conductor at the source.

If in this slide that Paul has posted the panel was being served with Non-Metallic Cable that contained the EGC in the cable then the System Bonding Jumper in the panel on the right would only serve the purpose of bonding

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.

We must remember that the main purpose of the Main/System Bonding Jumper is to establish a low impedance connection between the Equipment Grounding Conductor and the source in order to facilitate the opening of the Over Current Device in the event of a Ground Fault.

As pictured in Exhibit 250.13 of the Handbook the Equipment Grounding Conductors of the system is bonded to the Grounded (Neutral) through a conductor that is installed between the point where the Grounded (Neutral) is actually grounded to the Grounding Electrode System. This makes this conductor the System Bonding Conductor.






We must remember that the main purpose of the Main/System Bonding Jumper is to establish a low impedance connection between the Equipment Grounding Conductor and the source in order to facilitate the opening of the Over Current Device in the event of a Ground Fault.

As pictured in Exhibit 250.13 of the Handbook the Equipment Grounding Conductors of the system is bonded to the Grounded (Neutral) through a conductor that is installed between the point where the Grounded (Neutral) is actually grounded to the Grounding Electrode System. This makes this conductor the System Bonding Conductor.