Confusion regarding jumper cables NEC 250

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codequestion

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I have attached CCF09172017.jpg for this confusion. Figure 1 shows service equipment enclosure disconnecting means in which jumper is bonded to the enclosure from neutral bar. Figure 2 shows service equipment enclosure disconnecting means in which jumper is bonded to the enclosure from ground bar. Please see the attachment for system ground detail which is coming from neutral bar in service equipment enclosure. The incoming electric utility phase conductors and neutral (grounded service conductor) is incoming into the service equipment enclosure figure 1 and 2 but are not shown.

Question: which installment is correct per NEC 250 Figure 1 or Figure 2?
 

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In most cases, the bonding jumper would not even be required because the 'ground bus' would be directly secured to the enclosure with machine screws.

If I absolutely had to choose one over the other, Figure 2 is completely Code compliant.
 
codequestion said:
What is wrong with figure 1? How does figure 1 violate nec and what sections article? Also would installation cause problem?
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Debatable:

  • The service disconnecting means enclosure is service equipment, so bonding to the neutral is still permitted?
  • Code specifies one main bonding jumper per service disconnecting means enclosure(s)?
  • The EGC system according to Code is on the opposite side of the main bonding jumper from the neutral?
 
I believe the bar that hosts the neutral must have the bonding strap. Even though the ground bar is bonded to the neutral I don't believe the bonding strap to the enclosure can be there. When I have time I will look for the article
 
Depending on how the Ground bar is connected to the enclosure, would determine how many jumpers you would actually have.

If the Ground Bar was bolted to the enclosure in both options, then you've eliminated one of the jumpers shown in both diagrams.

Then your left with how you need to bond the Neutral.

I'd actually prefer Option 1.

From a possible failed connection standpoint, in my mind, you come closer to clearing a fault with Option 1 than 2.


JAP>
 
Ok would anyone know how to size the jumper cable shown on figure 1 and 2. I am NOT referring to main bonding jumper but the OTHER jumper cable. What table in NEC 2014?
 
codequestion said:
Ok would anyone know how to size the jumper cable shown on figure 1 and 2. I am NOT referring to main bonding jumper but the OTHER jumper cable. What table in NEC 2014?
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ActionDave said:
Anything before the first disconnect is 250.66 anything after 250.122.
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All jumpers at and after the service disconnecting means are sized per 250.102(C) in the most recent editions. Here's the header...
Table 250.102(C)(1) Grounded Conductor, Main Bonding
Jumper, System Bonding Jumper, and Supply-Side Bonding
Jumper for Alternating-Current Systems
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Note Code does not specify the size of a machine screw or bolt serving the purpose of a jumper.
 
Can anyone tell me in nec article which references table to use which says to use at disconnect for jumper cable shown on figure 1 and 2? I am NOT referring to main bonding jumper but the OTHER jumper cable.
 
codequestion said:
Can anyone tell me in nec article which references table to use which says to use at disconnect for jumper cable shown on figure 1 and 2? I am NOT referring to main bonding jumper but the OTHER jumper cable.
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If you are talking about not using the can as a neutral conductor that's in 200.2. There's not anything that tells you not to use a wire jumper.
 
ActionDave said:
200.2(B) Continuity
The continuity of a grounded conductor shall not depend on a connection to a metallic enclosure, raceway, or cable armor.
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Still don't see how that relates to the question. :blink:

(Please consider comment rhetorical :D)
 
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