Journeyman Electrician Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

To determine the minimum required ampacity for the feeder supplying both a continuous lighting load and a motor load, it's essential to apply the National Electrical Code (NEC) guidelines for calculating the total load correctly.

In this scenario, there is a continuous lighting load of 39 amperes. According to the NEC, continuous loads must be calculated at 125% of their rating when determining conductor size. Therefore, the calculation for the continuous lighting load is as follows:

39 amperes × 1.25 = 48.75 amperes.

Next, there is a motor load of 24 amperes. The NEC allows for the motor load to be calculated at 100% of its rating since it is not a continuous load. Thus, the motor contributes a full 24 amperes to the total required capacity.

Now, to find the total required ampacity for the feeder, the continuous load and motor load need to be added together:

48.75 amperes (for the continuous lighting load) + 24 amperes (for the motor load) = 72.75 amperes.

To determine the minimum ampacity required, it is prudent to round up to a standard available ampacity rating. The closest standard size above 72.