Electrical IBEW Practice Test 2025 - Free IBEW Practice Questions and Study Guide

To determine the maximum number of 15-amp circuits that can be fed from a 20-amp breaker, it's essential to understand the electrical load calculations based on the National Electrical Code (NEC) guidelines.

According to NEC guidelines, the general rule for circuit loading is that you should not continuously exceed 80% of the circuit's capacity for reliable operation. For a 20-amp breaker, this means that the maximum safe load it can handle is 16 amps (0.8 x 20 amps).

When you connect 15-amp circuits to a 20-amp breaker, you consider the total potential load that could be present if all circuits are fully utilized. Each 15-amp circuit can theoretically draw up to 15 amps, but under continuous load conditions, you should only consider about 12 amps per circuit (which is 80% of 15 amps).

To find how many 15-amp circuits can be connected without exceeding the capacity of the 20-amp breaker, you’d perform the following calculation:

1. Determine safe operating load for the 20-amp breaker: 16 amps.

2. Calculate the number of 15-amp circuits you can use:

- At the