Answer:
Calculating Wire/Cable Size Formula for Single-Phase Circuits
Wire Circular mils = 2 x ρ x I x L / (% Allowable Voltage drop of source voltage)
Calculating Wire/Cable Size Formula for Three-Phase Circuits
Wire Circular mils = √3 x 2 x ρ x I x L / (% Allowable Voltage drop of source voltage)
Where;
- ρ = Specific resistance or resistivity of Conductor
- D = Distance in Feet (One way) i.e. ½ the total circuit length
- I = Load Current
Note: The Value of ρ = Specific resistance or resistivity of Conductor is used here for copper and aluminum is 11.2 and 17.4 respectively at 53° C (127° F).