HOLT Electricians Practice Exam

The feeder protection device must be greater than which branch circuit protection device?

1. Largest branch circuit

2. Sum of all currents

3. Smallest branch circuit

4. Average of all branch circuits

The correct answer is: Largest branch circuit

The correct answer indicates that the feeder protection device must have a rating that is greater than the largest branch circuit protection device. This is essential for ensuring that the feeder can handle the maximum load that could be drawn from any branch circuit without tripping unnecessarily or becoming a point of failure. In a typical electrical system, feeders are designed to supply power to multiple branch circuits. If the feeder protection device is rated lower than the largest branch circuit, it may trip during normal operation when that branch circuit draws its maximum load. This would lead to nuisance tripping and could disrupt service to other branch circuits. Thus, designing the feeder protection device with a rating that exceeds the largest branch circuit ensures that the feeder can adequately manage the total load potential, while still allowing the individual branch circuit protection devices to trip under overload or short circuit conditions for their respective circuits. This creates a balanced and reliable electrical system while optimizing safety and functionality.