BGK, Justin's figures are accurate. "BUT" if you plug in #6 to the VD formula it comes up just a shade over 5% VD. With everything being said you want the smallest amperage (15 or 20) that will addequately support your load without nuisance tripping all of the time. which ambient temperature swings based on the time of year will cause your amperage to fluctuate slightly.
So alot rides on the size of wire you ran.
