141022-0917 EDT
GoldDigger:
The hot bus bars in my 200 A QO panel are about 1/4" x 3/4" and I believe copper. These are not going to heat much as a result 200 A, but certainly serve as a heatsink to the breakers. The neutral bars are about 1/4" x 1/2" with a large part of the cross-section removed for the wire holes. Net cross-section in a large part of the bus is about 1/4" x 1/8".
The neutral bus consists of two bars and these are fed from two perpendicular bars spaced at about 1/3 points. Thus, the current to different parts of the bars is possibly 1/8 of the total neutral current.
How this balances out is hard to predict without actual measurements with wiring of some sort of worst case situation.
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