Hi Guys, I am doing a 600a 1phase service and I was going to use 350kmcm in parallel, my friend from a diffrent firm is telling me they used 300kmcm for one just recently. Now I am second guessing myself, so I am turning to you all.
If in two seperate conduits 300 kcmil is good for 285 amps at 75c. see 240.4 (b) (800 amps or less next higest breaker size) . 240.6 300 next breaker size is 600. 285 plus 285 = 570 if in one single conduit see table 310.15(B)(2)(a) 4-6 80% 570x80%=456 next higest per 240.6= 500amp. Same Conduit would require 400 Kcmil 335x2= 670 x 80%= 536 . 240.6 next higest 600 This is with 3 wires in conduit single phase. Or 6 wires in conduit single phase.