assuming 240 volts, 3% VD would be 7.2 volts
VD = 2 x I x L x R / 1,000, using the R per 1,000 feet in Table 8, Chapter 9.
Transposing: max R = 1,000 x 7.2 volts / 2 x I x L
L = 169 feet
I = 21 amps (or 25 amps with lights?)
so max R would be 1.1 to .85 ohm which means a #8 copper conductor would be required. (.809 ohm per 1,000 feet)
Neutral could be downsized for 240 volt load.
If you are running 120 volts, then maximum VD would be 3.6 volts.
and max R would = 1,000 x 3.6 / 2 x 25 x 169 = .42 ohm, which corresponds to a #4 copper conductor.
If you run less, you risk low voltage to appliances. Problem??? maybe, maybe not.
