Sub Panel Grounding

[Adam Spade]

For a 480Volt, three phase, 4 wire subpanel in an equipment room, the electrical contractor has installed 350kmil single cables run in metallic conduit ( its a long run )He has installed a 4/0 ground wire , run in with the 350's. He says providing he bonds the ground with the neutral at the subpanel and installs a ground rod as well the 4/0 is good. your comments please

 

[George Stolz]

If there is an EGC run with the feeder, there is no instance where the subpanel can have it's neutral bonded to the EGC. This is a 250.6 and 250.24(A)(5) violation.

I didn't check the sizing of the EGC, but we would need to know the size of the breaker supplying the feeder to ascertain if it were sized correctly or not anyway.

 

[infinity]

Is this in a separate structure? The metallic raceway can serve as the EGC. Just keep the neutral and EGC's separate at the subpanel. The ground rod isn't required if this is in the same building as the origin of the feeder.

 

[SEO]

If you bond the ground wire to the grounded conductor at a feeder panel you are in violation. See section 250.142 (A) & (B).