Main bonding jumper size

[hhsting]

I have 5 sets if #400 service conductor incoming into switchboard. The main bonding jumper size shown is 5-1/0 awg in parallel.

I see that 5x400= 2000 and 2000*.125 = 250 kcmil size main bonding jumper.

When I see 5-1/0 awg thaf equal to 105560*5=527.8kcmil which is greater than 250kcmil required size

However i wanted to make sure. Can one have 5 - 1/0awg in parallel as main bonding jumper or not?

 

[infinity]

No MBJ's can't be paralleled. Your calculation provided the correct size. Are you sure these #1/0's aren't SSBJ's?

 

[hhsting]

No MBJ's can't be paralleled. Your calculation provided the correct size. Are you sure these #1/0's aren't SSBJ's?

Yes I am sure these are main bonding jumper and NOT SSBJ. see below snap shot. The engineer also has provide grounding electrode conductor 5-#1/0 awg.

Where in NEC 2017 it says main bonding jumper cannot be paralleled?

 

[roger]

Well besides the fact that the designer is a clown the gear should have a MBJ included in the form of a strap

 

[infinity]

Where in NEC 2017 it says main bonding jumper cannot be paralleled?

Where does it say that it can?

 

[Johnhall30]

5#1/0 to a ground rod. Lol

 

[hhsting]

Where does it say that it can?

True I cant argue that with designer. If its not in code somewhere how can it be enforced?

 

[kkyyllee]

250.68 (a)
(A) Material
Main bonding jumpers and system bonding jumpers shall be of copper or other corrosion-resistant material. A main bonding jumper and a system bonding jumper shall be a wire, bus, screw, or similar suitable conductor.

 

[roger]

250.68 (a)
(A) Material
Main bonding jumpers and system bonding jumpers shall be of copper or other corrosion-resistant material. A main bonding jumper and a system bonding jumper shall be a wire, bus, screw, or similar suitable conductor.

The material is not being questioned and you might want to check your reference.

 

[LarryFine]

True I cant argue that with designer. If its not in code somewhere how can it be enforced?

Because following the approved plans is also enforced.

 

[kkyyllee]

The material is not being questioned and you might want to check your reference.

I see i made an error should be 250.28. I was reading as all items listed are singular

 

[infinity]

True I cant argue that with designer. If its not in code somewhere how can it be enforced?

The NEC {250.102(C)(1)} tells you how to size the MBJ. It doesn't say that you can use multiple smaller conductors to make a larger one. Also looking at the drawing the multiple #1/0's is likely an error.

 

[hhsting]

The NEC {250.102(C)(1)} tells you how to size the MBJ. It doesn't say that you can use multiple smaller conductors to make a larger one. Also looking at the drawing the multiple #1/0's is likely an error.

It doesnt but it also doesnt say you cannot especially note #1 Table 250.102(C)(1) 5 sets of#1/0 awg total area is greater than 250kcmil.


I searched thru some old posted by someone else and I believe you had said in those post NEC 2017 Article 250.24(B)main bonding jumper must be unspliced and by paralleling them one is creating splice. See the link below post#4:

Main Bonding Jumber

I have (10) sets of 600KCMIL conductors going to 4000A service. Per 250.29.D, we have to use minimum of 750KCMIL as main bonding jumber. Can I use parallal jumbers, in another word, can I run (2)400KCMIL instead of (1)750KCMIL? Thank you.

forums.mikeholt.com

Sounds reasonable to not have parallel main bonding jumper?

 

[infinity]

It doesnt but it also doesnt say you cannot especially note #1 Table 250.102(C)(1) 5 sets of#1/0 awg total area is greater than 250kcmil.

It says that you calculate the bonding jumper (singular) size by the 12.5% rule. There is no wording that would suggest that multiple conductors can be used. Since you're doing plan review mark up the violation and send it back. The GEC to the water pipe is also wrong. The ground rods and CEE conductors are above the minimum required for a single conductor so there is no issue with them.

Table 250.102(C)(1) Grounded Conductor, Main Bonding Jumper, System Bonding Jumper, and Supply-Side Bonding Jumper for Alternating-Current Systems

Notes:
1. If the ungrounded supply conductors are larger than 1100 kcmil copper or 1750 kcmil aluminum, the grounded conductor or bonding jumper shall have an area not less than 121∕ 2 percent of the area of the largest ungrounded supply conductor or equivalent area for parallel supply conductors.