winnie ----

I use different numbers:

wire 60C A mO/ft Watt/ft
14ga 15 3.13 0.70
12ga 20 1.98 0.79
6ga 50 0.49 1.23
4ga 66 0.31 1.35 (66 is a strange amp)

2" PVC conduit dissipates 12.1 watt/ft (based on 15 4ga - 9 current carrying)

This allows (current carrying conductors) 17 14ga, 15 12ga, or 10 6ga (based on heat dissipation) WITH NO DERATING FROM THE ABOVE AMPS.