I have purchased a metal building 100' X 50'...there is a 200 amp main at one end. I want to install a 100 amp sub-panel at the other end. What size wire do I need? Do I just install a 100 map double pole breaker in the 200 amp box to feed the new 100 amp sub-panel? And, there is a total of 12 12AWG wires already going from the 200 AMP main to the other side of the building that was use to feed some gas pump cut-offs. Can I use these wires to energize my 100 amp sub-panel, maybe triple the wires up to make them more like a size 4 or 6 awg? I know it sounds strange, but large AWG is so expensive, I could save some dough. Any help would be awesome!!