Why might a branch circuit require both a fuse and a circuit breaker?

A branch circuit may require both a fuse and a circuit breaker to provide higher protection or redundancy for specialized equipment. Each device serves a different purpose in protecting the electrical system. Fuses are designed to interrupt the circuit quickly in case of overcurrent conditions, offering a level of protection to sensitive equipment by responding to fault conditions faster than circuit breakers in some scenarios.

On the other hand, circuit breakers offer reset capability, allowing for quick restoration of service after a fault condition has been cleared. This dual-layer protection is beneficial for systems with critical or specialized equipment that may be at risk during overload or fault conditions. By employing both devices, you enhance the overall safety and reliability of the electrical system, ensuring it can handle specific operational demands while still providing a fail-safe mechanism.

While compliance with local electrical codes and cost considerations can influence the design of an electrical system, the primary reason for using both a fuse and a circuit breaker is to enhance protection and ensure reliability for specialized applications.