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!!

Hi akarka,

only an electrician can accurately answer that question. I'm sure a [nice] electrician could answer that question for you over the phone. I would assume that their answer would be no, but it's worth a shot...

that being said... (and BTW, I am not an electrician)

if you "triple up" 3 x 12AWG wires you would theoretically have the diameter of a 2.5AWG wire (if such a size existed), however I would think that bunching up insulated wires together would increase the resistance so much that it would greatly reduce the ampacity of the wires over a 100 foot span. this could potentially cause a fire hazard (especially if the wires are not run inside metal conduit).

in any case, even if it's theoretically/mathematically possible... I doubt that it would be legal to do it. so my advice (for what it's worth) is to contact an electrician to find out what wire gauge and wire type to use.

good luck and be safe