A 240-volt feeder supplying twelve 120-volt, 30A shore power receptacles requires a minimum ampacity of _____ amperes if the demand factor is 80%?

• A. 120 Amperes
• B. 144 Amperes
• C. 200 Amperes
• D. 180 Amperes

Answer: (B)

To determine the minimum ampacity required for a feeder supplying multiple receptacles, you must first consider the demand factor and the total load. In this scenario, you have twelve 120-volt, 30A shore power receptacles.

1. Calculate the total load: Each receptacle can draw a maximum of 30 amperes at 120 volts. For twelve receptacles, the maximum possible load would be:

[

\text{Total load} = 12 , \text{receptacles} \times 30 , \text{A} = 360 , \text{A}

]

2. Apply the demand factor: The demand factor is typically a consideration that accounts for the fact that not all devices will be in use simultaneously. In this case, you're given a demand factor of 80%, which means you need to calculate 80% of the total load:

[

\text{Adjusted load} = 360 , \text{A} \times 0.80 = 288 , \text{A}

]

3. Adjust for feeder capacity: Since this is a 240-volt feeder supplying 120-