I have an instructor telling me that to do a VD calc, you use the following formula:
VD=(Amps x 1 way Length x R)/1000'
Where R = ohm/kFt from NEC Ch 9, Table 8
It seems to me like you would have to double the length since we are only counting the resistance in one direction...is this correct? I have always used the online calculators, and I'm trying to learn how to do it on paper.