Electron_Sam78
Senior Member
- Location
- Palm Bay, FL
Ok I thought I had a handle on voltage drop but I'm stumped. I'm helping someone with a calculation and something doesn't add up. We have 6 each 30 amp loads totaling 180 amps at 120 volts. Two 90 amp circuits (one 2-pole CB, sharing neutral) running 240 feet comes to 250 mcm for roughly 3% max VD with Al conductor at 120 volts.
But he suggested a "90 amp sub-panel" close to the loads and input it in the calculator using 240 volts as the system voltage and it output wire size of 2/0 Al for roughly 3% voltage drop for the same length run. This doesn't seem to add up to me but can't figure out why for the life of me. Maybe it's been too long of a day :blink:
If there were no VD to account for I'd run the same size wire to feed a 240 volt, 90 amp sub-panel as I would a 120 volt, 90 amp circuit. Should I input the total amperage at 120 volts (180a) then use 240? Grr I need some sleep.
But he suggested a "90 amp sub-panel" close to the loads and input it in the calculator using 240 volts as the system voltage and it output wire size of 2/0 Al for roughly 3% voltage drop for the same length run. This doesn't seem to add up to me but can't figure out why for the life of me. Maybe it's been too long of a day :blink:
If there were no VD to account for I'd run the same size wire to feed a 240 volt, 90 amp sub-panel as I would a 120 volt, 90 amp circuit. Should I input the total amperage at 120 volts (180a) then use 240? Grr I need some sleep.