Hello & welcome to ECN!
First question (although not an NEC item) I have is why would 16 conductors be installed in one conduit, going to four (4) different places?? Did your Instructor require you to do it this way??
Second is what is the amperage of the sub panels/feeders?
Based on the info you posted...I'm going to guess the panels are 3 phase, 4 wire? Or...are you doing single phase, 3 wire, with a full size ground?
If, 3 phase, 4 wire, does the neutral have to be considered a current carrying conductor based on the type of loads in the sub panels?
You can't solve anything without all the required info!
I suggest you gather the missing info and.....
Determine a starting AWG based on the amperage.
Derate from 310.16 amps, based on the number of CCC's per 310.15 (b)(2)(a) table.
Then do Vd calcs after completing the above.
If you need additional help/info/suggestions let me know.
Additional opinions from other members should arrive soon
