Multiple grounding conductors under a single log

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Hello everyone. I was hopeing I could get a discussion settled I've been having with a coworker.

I'll try to keep only the essentials in my story. We just ran a 500kcmil 3 conductor cable (so 3-500's) and inside that cable are 3 grounding conductors (I don't know their sze off the top of my head) and it's wrapped in a copper shield before being wrapped in the typical insulation. This cable goes between a 250hp motor and an MCC. At the MCC, which has 3 terminals for the unfrounded conductors (brn, org, yel) and one for the grounding conductor.

My question is this, since these three grounding conductors are common to each other, can all three wires go under the same single-barrel lug (which clearly is rated to hold the total kcmil of the sum of their kcmils), or di I need to put one under it and put the pther two under a double barrel lug grounded to the panel?

If anyone is able to finda reference that explains their answer, it would be appreciated so I can make the point to my coworkers.

Thank you!
 

brian john

Senior Member
Location
Leesburg, VA
What does the lug say one, two or three conductors allowed? I would bet at most two, IF LISTED for two conductors. I cannot think of and single hole lugs rated for three conductors, but I have been wrong before.

From an electrical stand point the metallic connections could care less al long as there is a decent connection.
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
What does the lug say one, two or three conductors allowed? I would bet at most two, IF LISTED for two conductors. I cannot think of and single hole lugs rated for three conductors, but I have been wrong before.

From an electrical stand point the metallic connections could care less al long as there is a decent connection.

I just bid a job where they had several motor feeds from an MCC to the motors. All fed with tray cable. Some motors had cable 3#10 with 3-#16 grounds, and others had 3-#10 with #10 ground. As this is in the ballpark of this question, why? And isn't that a sort of violation of the NEC for not having a grounding conductor sized to 250-122?
 

jumper

Senior Member
I just bid a job where they had several motor feeds from an MCC to the motors. All fed with tray cable. Some motors had cable 3#10 with 3-#16 grounds, and others had 3-#10 with #10 ground. As this is in the ballpark of this question, why? And isn't that a sort of violation of the NEC for not having a grounding conductor sized to 250-122?

Your cable may have been legal as far as the EGC if it met 310.10(H)(5)

(5) Equipment Bonding Conductors. Where parallel
equipment bonding conductors are used, they shall be
sized in accordance with 250.122. Sectioned equipment
bonding conductors smaller than 1/0 AWG shall be permitted
in multiconductor cables, provided that the combined
circular mil area of the sectioned equipment bonding
conductors in each cable complies with 250.122.
 
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