My dad and my uncle were wiring in a disconnect & panel in my dad's new shop the other day. It is a 600v 400A 3-phase connection. When they were wiring the 3 phase connection from the main disconnect to the panel, my uncle (whose an electrician) says to make all the conductors the same size. He said that if you don't, the shorter conductor of the 3 will get really hot. Is there any reason to why he would say this? I can't think of any reason unless maybe the cable was longer...instead of shorter. Then the increased resistance may cause the conductor to heat - not sure. Any ideas?