To limit the Voltage drop to 3% I use the formula: R = 15 x E / I x L
E = 240 volts
I = 100 amps (worst case)
L = 175 feet
R = 15 x 240 / 100 x 175 = .2057 ohms
I want a conductor with a maximum resistance of .2057 ohms per 1,000 feet. Looking at Table 9, Chapter 9, I see that for PVC conduit, I need #2 copper or 1/0 Aluminum. Checking with Table 310.16, I see that #3 copper or #1 Aluminum are the minimums, so I choose #2 copper or 1/0 Aluminum.
Earl
