250.102(C)(1)

[Isaiah]

The engineering firm has undersized the supply side bonding jumper from the transformer secondary to the Swgr CB. Can engineering calculations suffice per NEC 240 versus performing a lot of rework?

They’re running 500kCMIL, 13 per phase in multiple 4” underground PVC conduits and each conduit has a #2/0 bonding jumper...BUT according to 250.102(C)(1) it should be 12.5% of the total kCMIL area i.e. 13x500kCMILx.125=812kCMIL


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[augie47]

For SSBJ see 250.012(C)(2).
With parallel conduits you can base the size on the conductors in each conduit.
Your MBJ would be based ion the 12-1/2%

 

[Isaiah]

For SSBJ see 250.012(C)(2).
With parallel conduits you can base the size on the conductors in each conduit.
Your MBJ would be based ion the 12-1/2%

Thanks Augie


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[infinity]

For copper 500 kcmil only a #1/0 is required in each raceway.