A panel for a commercial building is supplied by a 500 ft four-wire 208Y/120-V three-phase feeder. The panel serves three major loads:

• A lighting system of a total power of 70 kVA with a power factor of 0.8

• 500 receptacles connected to loads with an average power factor of 0.90

• Heaters rated at 17.5kVA and a power factor of 1.00

• Several motors with a total power rating of 20-kVA and a power factor of 80% with the largest motor rated at 50 kW and a power factor of 0.85. 

Determine:

(a) The size of the feeder and conduit using THW copper conductors.

(b) The voltage drop in the feeder. (Assume a steel conduit.)

(c) The size of the feeder and conduit that limit the voltage drop to 1%.