Final answer:
To determine the smallest size copper THW wires for the 3-phase 120/208 service, calculate the load in amperes using the formula Load (VA) = Voltage (V) x Current (A). Refer to a wire size chart to find the smallest suitable wire size.
Step-by-step explanation:
To determine the smallest size copper THW wires that can be utilized for the 3-phase 120/208 service, we need to calculate the load in amperes. The formula to calculate the load in amperes is Load (VA) = Voltage (V) x Current (A).
Given that the total load is 54,000 VA and the voltage is 208 V, we can rearrange the formula to solve for the current. Current (A) = Load (VA) / Voltage (V) = 54,000 VA / 208 V = 259.62 A (approximately).
Based on the current, we can refer to a wire size chart to find the smallest size copper THW wire that is suitable. From the options provided, the smallest size copper THW wire that can be utilized for the 3-phase 120/208 service is #12.