Four Four inch from utility Transformer to CT Cabinet then to MCC. (XHHW).
three 600MCM & one 350 MCM each Conduit .
600 at 75C 420 amps x 4 = 1680 amp.
Very low Neutral load mostly 480 volt loads.
Using 310.15 (5) so no derating.
Engineer wants to use six six inch with four 400 mcm in each conduit.
I think conduit way over sized!