A panel for an office building is supplied by a 200 ft four-wire and a 480Y/277 V feeder. The loads of the panel include

• A lighting system of a total power of 10 kVA with a power factor of 0.8

• 100 receptacles with an average power factor 0.90

• Heaters rated at 7.5 kVA and a power factor of 1.00

• Several motors with a total power rating of 40 kVA and a power factor of 80% with the largest motor rated at 5 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 expressed in %. (Assume a steel conduit.)

(c) The size of the feeder and conduit if the voltage drop is limited to 1%.

(d) Would the size for the feeder found in (c) change if the symmetrical short-circuit current is 20,000-A and a circuit breaker is used to protect the feeder? Show your calculations.