400 A 3 phase pnl 208/120 volts

[Rlmwireman]

I have a 400 amp disconnect feeding
A 400amp main panel w main.
I gonna run 2 set of 3/0 to 400 amp
Main panel. What size ground in each
Set table 250-122 or 250-66
Thanks

 

[roger]

250.66 is for GEC's, 250.122 is for EGC's, see the definitions of each in article 100.

Out of curiosity, what year code book are you referencing?

Roger

 

[charlie b]

What is upstream of the 400 amp disconnect, and is that disconnect fused? If the answers are "utility-owned transformer" and "no," then the "ground thingy" would be neither a GEC nor an EGC. It would be an SSBJ, and would be sized per 250.102(C).