I have seen this done several times before by other companies, and not sure what to really think about it.....
Say you have a 3 phase 42 circuit panel, with all 20a circuits...
And you run all 42, and thier neutrals out of it in only (4) 1" conduits using this method 50 or so feet to J-boxes and gutters and dropping to #12 for the rest of the circuit.
Table 310.16 for #10 THHN is 40a. (Without load diversity)
Table 310.15(B)(2)(a) for 10-20 conductors is 50% derating. Down to 20a on #10.
Table C1 for #10 is 16 in 1"EMT.
42 circuits, and 14 neutrals is 56 conductors, divided by 16 is 3.5 conduits.
And if in 1 1/4" you could do it in (2) conduits.
What do you think of this practice?
(Cost of Steel and Labor?)
(Cost of Copper, and 56 splices in a bunch od cans?)
(Circuit Quality?)
