What is the total ampere rating of a feeder supplying a continuous lighting load of 45 amperes and a single motor load of 30 amperes?

To determine the total ampere rating of a feeder supplying both a continuous lighting load and a motor load, it’s crucial to apply the NEC (National Electrical Code) guidelines. According to NEC requirements, continuous loads must be calculated at their full value and then increased by a certain percentage to account for continuous use.

In the scenario, the continuous lighting load is 45 amperes. For continuous loads, the code states that you should add 25% to the load to ensure the system can handle it without risk of overheating or failure. Therefore, 25% of 45 amperes is calculated as follows:

[ 0.25 \times 45 = 11.25 \text{ amperes} ] Adding this to the original continuous load gives:

[ 45 + 11.25 = 56.25 \text{ amperes} ]

Next, the motor load is 30 amperes. For this voltage rating, motors are typically taken at their full load current without an additional increase. Thus, the motor load remains as is at 30 amperes.

Now, the total load on the feeder becomes the sum of the adjusted continuous load and the motor load:

[ 56.25 + 30 = 86