750kcmil ground on 4000a feed that is paralleled 12 times

[bennettg77]

I know 250.122 calls for a ground wire to Al. 750kcmil for a 4000a feed. This feed is for the generator to the MSB. wouldn't
this fall under 250.66 and on need to be Al. 3/0?

The drawings show:

12 sets of 4-600kcmil, 750kcmil G, 4"C

I don't ever re-call pulling a ground that is larger than my ungrounded conductors.

Thank you

 

[augie47]

The 750 would be correct for a 4000 amp feeder.
At one time I was under the impression that the EGC would not be larger than the phase conductors based on 250.122(A), however, it was explained to me that with parallel feeders a short would be fed from all sources so the 250.122 required size would be correct.

 

[bennettg77]

The 750 would be correct for a 4000 amp feeder.
At one time I was under the impression that the EGC would not be larger than the phase conductors based on 250.122(A), however, it was explained to me that with parallel feeders a short would be fed from all sources so the 250.122 required size would be correct.

Thx Aguie47. Thats the way it was explained to me as well.

 

[don_resqcapt19]

Does the feeder originate at the generator output terminals or at an overcurrent protective device at the generator?
It is originates at the generator output terminals and not an OCPD, then the conductor in question is a supply side bonding jumper and us sized based on the maximum size conductor in each raceway per Table 250.102(C)(1).

 

[Tulsa Electrician]

Here is a quick drawing.
If I'm understanding correctly
Breaker in generator

 

[don_resqcapt19]

Then you are stuck with the rule that requires the 750 kcmil EGC and that will also apply to the four set of 600 kcmil that are tapped off of the main run.

 

[Tulsa Electrician]

Thank you