Wiring Subpanel off Subpanel
I want to put a small subpanel in a pole barn. I have a few questions.
The house has 200 amp service. The main box has a double 100 amp breaker on 2 gauge wire to a subpanel in the garage. The distance from the panel in the basement to the panel in the garage is approximately 50 feet. The garage has a 100 amp box.
We built a small pole barn about 50 feet from the garage. I want to wire the pole barn with a few outlets (one for a garage door opener) and lights and a 30 amp outlet for a camper. I would like to put a small panel in the pole barn with two breakers - 30 amp for the single RV outlet and 20 amp for the lights and opener. The kids use the camper for sleep overs and the stone pad is between the garage and pole barn.
The distance from the garage subpanel to the proposed pole barn subpanel is about 110 feet, and the proposed pole barn subpanel is about 160 feet from the main box in the basement.
(1a) If I follow this setup, can I run 8/3 with ground from the garage box to the pole barn box? Or do I need 6/3?
(1b) Do I still use just a double 30 amp breaker in the garage box?
(1c) In the pole barn, after the breaker, do I get to use 10 gauge and 12 gauge wire for the two circuits? I understand and can calculate voltage drop, but am unclear on what happens when we start putting subpanels in the middle. The garage was wired by an electrician and he used 12 gauge wire on the 20 amp circuits and 10 gauge on the unused 30 amp.
(2) Just to confuse matters, if I install an RV post box (like they use at the campground) on the back side of the garage, I shorten the distance from the garage box to the RV box to about 50 feet. I should be able to just run 10/2 wire to the RV box with a 30 amp breaker in the garage, and run 10/2 to the pole barn to power the outlets and lights. Can I run a single 10/3 wire to the RV box, using the black for the RV box, and then continue to the pole barn with 10/2 connected to the 10/3's red, white, and ground? I don't think this is the best way, but I already have an unused 10/3 Romex from the garage box into the garage attic that was intended for an electric heater. We installed a propane heater instead.
Thanks for your patience and suggestions.