what size pull box would I need if I have 3 4 inch conduits on one side and going out the back with 3 4 inch condits all having 4 600 mcms in them with a removable cover.. I came up with a box of 36x36x8 please help??
First...Welcome to ECN from one of the "Jersey Guys"!!
Based on 314 and reference back to 312.6(a) for the removable cover, you got it.
That said, think about the actual layout you intend. The 8" depth may be a battle with the 600s, as the 36" side to side space. Keep in mind the result of the 314/312 calcs is the 'code minimum', and not the "ultimate" answer.
You may decide on a 40" or 48" x 12" box.....think ease of install, possible labor savings, and 'for sure' code compliance.
36" is w a a a y too long if you're going in one face -- and plunging out the back side. "and going out the back"
600 kCMIL is brutally stiff -- even in aluminum -- so I could never recommend going with 8" as a depth.
You are not providing ANY of the circumstances that would dominate my own can sizing -- which is never predicated upon the NEC minimums. (I never, ever, attempt to squeeze (feeder) conductors into spaces so tight.)
Lowest cost means that the actual installation goes off without a hitch. That will not happen with NEC minimums. Tight space takes extra time... sometimes amazing amounts of extra time.
The NEC permits 9 #12 THHN in 1/2" EMT. Only a fool would design to such a scheme. Five #12 is the maximum that one would want to run in 1/2" EMT. Nine #12 -- going through four full nineties -- may require use of a power tugger. Yes, it can get that bad. Pulls like that cause the back injuries so common to electricians.
2011 NEC 600 Volts & under . 314.28 A (2). 6 x 4 =24 + 8 = 32 inch by 32 inch. Depth see 314.28 A (2) exception . That refers you to 312.6 (A). 70-175. Wire per terminal 3. 600-700 wire per terminal = 12 inch Depth.
As Said by others . that is Minimum size! If you ever pulled 600 mcm you would NOT use minimum size.