Main bonding jumper

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hhsting

Senior Member
I have 11 sets of 750kcmil Al conductors going into 3000A main service switchboard.

11x750=8250 kcmil

8250x0.125=1031.25 kcmil


The plans the main bonding jumper of 2 sets of 600kcmil Al which would yield 1200kcmil Al total since they are in parallel

So whats the problem?

I thought the main bonding jumper need to be unspliced according to 250.24(B). Does anyone know you can do sets of main bonding jumper in parallel or not? Am I missing something? Its going to be wire not manufacturer provided bus or other manufacturer provided items I already inquired with designer
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The code does not specify either way.
I do not see how parallel conductors equal a splice.
I see no issue with the parallel conductors, but if you do, mark the drawing up and send them back to the engineer.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I've never seen a 3000 amp servcie switchboard without a factory installed piece of bus serving as the MBJ.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I've never seen a 3000 amp servcie switchboard without a factory installed piece of bus serving as the MBJ.
agree. If it does not have a factory MBJ I would be suspect that it's not listed as service equipment
 
Last edited:

hhsting

Senior Member
The code does not specify either way.
I do not see how parallel conductors equal a splice.
I see no issue with the parallel conductors, but if you do, mark the drawing up and send them back to the engineer.

Engineer is the on who has shown 2 sets of 600kcmil AL. Engineer says they dont provide bus as MBJ

Curious how do you not see parallel sets of MBJ not a splice? They do have to connect together at ends how are they not splice?
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
It's two conductors terminated at each end. A termination is not a splice.

But I agree with the others. I've never seen any labeled as suitable for use as service equipment without a factory provision for the MBJ. At least, nothing under 30 years old. Is this new equipment?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Engineer is the on who has shown 2 sets of 600kcmil AL. Engineer says they dont provide bus as MBJ

Curious how do you not see parallel sets of MBJ not a splice? They do have to connect together at ends how are they not splice?
Get out the red marker, cross out the two sets of 600's and add a note that the MBJ must be a bus bar equivalent to 1031 CM and send it back.
 

Tulsa Electrician

Senior Member
Location
Tulsa
Occupation
Electrician
Since it (MBJ) is not supplied. Is the equipment service rated?
I just assumed it was since your installing an MBJ and stated main service switchboard.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Engineer is the on who has shown 2 sets of 600kcmil AL. Engineer says they dont provide bus as MBJ

Curious how do you not see parallel sets of MBJ not a splice? They do have to connect together at ends how are they not splice?
A splice is a connection that extends the length of a single conductor, making it one longer conductor. A splice is between the two ends of a conductor. A set of parallel conductors cannot in any way be construed as being a splice.
 
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