I will be running my service (208v-3phase-300 amp) to an office building next week. The run is 100 ft. from poco transformer to meter base, and around 80 feet from meter to the 300 amp main. The engineer specs 350 mcm for the run. With copper going through the roof I cant see why I shouldnt be able to run 300 thhn. Total connected load is around 225, no electronics. I did a vd calc and 300 keeps me well within the 3%. Its a 4 wire system, but 310-15-4 states the neutral is not considered when it is used to carry the unbalance. Is there something obvious that I am missing? Thought I would ask, before I call the engineer.
Thanks, John