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.


Ob

300KCMil Copper, 75 degree col is 285 amps,Based on 240.4 (B)parallel is 570 amps, next higher available is 600 amps.

300's work.

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.