[gatormike58]

What size wire must be run for 6 - 30amp sub pannels 350' away from 100 amp main?

[donf]

Will the six additional panelboard be in the same building or are they going to be in outside buildings?

You do understand that you are going to be pulling a maximum of 180 amps away from a 100 amp main panelboard.

Without additional information from you, I would speculate that you need 4 ea. of #8 copper conductors. This is ONLY if the conductors are inside the same building.

[tkrussell]

I do not know why if the wiring is inside or outside would make a difference regarding voltage drop.

To do voltage drop calculations, need to know the supply voltage and the actual load in amps or wattage.

Assuming 240 volts at 30 amp load, #4 copper is needed.

If 120 volts at 30 amps, then #1 copper wire is needed.

Can you explain further why 6-30 amp feeders are needed to go 350 feet?

[donf]

Knowing whether the wiring is inside or not will further define the method for grounding at the secondary panelboards.

T.K. What wire size calc are you using? I set mine to 240/30 using copper. The distance was 350' and it comes up with #8 conductors (voltage drop of 6.8%)