I bought an old farmhouse last year and I'm finally getting around to
fixing up some of the out buildings. The two that I'm working on now
each have power that comes from the main breaker panel in the house.
Each building has it's own fuse box with wiring extending from that.
Now on to the problem.

In the main breaker panel there are two seperate 30 Amp breakers that
each have a very large wire coming out of them. They aren't connected
like a double pole and aren't next to each other like a double pole
breaker. The two wires run into a single cable along with another
large wire wired to the neutral bus. The label on the cable is
"E32071 (UL) 3 CDRS AWG 6 TYPE SE CABLE STYLE U TYPE XHHW CDRS 600V".
Now, the cable goes out of the house and through the air to the first
building (Building A). Outside Building A there are severla wired
wired and taped together. One of the hot wires runs into bulding A
and the other wire splits into building A and also heads off to the
other building (Building B). Inside building A there is a fuse box
and the hot and neutral wires run to the normal connections. The
other hot wire and the split from the netural run through the air to
building B where the neutral and other hot wire run into a fuse box
and throughout the building.

Now for the question. I would like to replace the wires in the air
from A to B and replace the fuse boxes with a circuit panel. What I'm
considering is running both hots and the neutral into a 6 circuit
panel inside Building A and then running 1 circuit in A and 3 circuits
over to B through some underground conduit. The other issue that I
see is that currently at the splice outside building A the heavy wire
is spliced to some smaller old wire, it looks like around 10 gauge,
that runs from the outside into the building. I'm guessing that if I
splice the heavy wire coming from the house to a line into Building A
I need to keep it the same guage, right?

Sorry for the long explanation, but I wanted to try and explain the
situation better. If a picture would help, I can sketch one quick and
post it to my website. Any thoughts that you have would be great.

Thanks,
Nate Baxley