NEC Commercial Electrical Practice Test

If feeders with a common neutral are permitted, how many sets of wire feeders can they serve?

1. 2

2. 3

3. 4

4. 5

The correct answer is: 4

The correct choice indicates that feeders with a common neutral can serve up to four sets of wire feeders. This is based on the National Electrical Code (NEC) regulations regarding the use of a common neutral in feeder systems. According to NEC guidelines, a common neutral can safely serve multiple feeders, provided that the combined neutral current does not exceed the capacity of the neutral conductor. The Code typically allows for a maximum of four sets of feeder conductors to utilize a single neutral because of the balancing effect of the currents on the different phases. When circuits are balanced in terms of their load, the neutral current can be significantly reduced, making it a more efficient use of the wiring infrastructure. This practice is grounded in the principle that for multi-phase systems, the return current in the neutral conductor will be lower when the loads are evenly distributed across the phases. In summary, allowing four sets of wire feeders to utilize a shared neutral adheres to safety and efficiency standards established by the NEC, ensuring that the system can handle the respective loads without overheating or becoming a potential hazard.