Quote Originally Posted by Adamjamma View Post
Well, he said 3 phase, 100 amps... so that starts around what, number 2... copper thhn is what I am assuming cooper think means but...of course, now you have the three conductors in a tray or such so you have derating and the 500 feet with 75 degree connections....2/0?.
If only 3 conductors there is no adjustment necessary. 3AWG is good for 100 amps 75C.

What is not real clear is if the load is 100 amps or if it a 100 amp feeder with a lesser load on it, as well as what is continuous, what is non continuous for load. Once one knows absolute minimum conductor needed then comes how much voltage drop is acceptable and can the minimum ampacity conductor provide that or not.