There are several compelling reasons for replacing fused disconnects with enclosed rated circuit breakers:
Resettability: Circuit breakers can be easily reset after tripping, whereas fuses need to be replaced. This saves time and reduces maintenance costs.
Common trip functionality: Circuit breakers provide common trip for all phases, preventing single-phasing conditions that can damage three-phase motors. Fuses do not offer this protection.
Environmental resilience: Circuit breakers are less susceptible to performance degradation caused by factors such as high ambient temperatures, humidity, and vibration compared to fuses.
Space efficiency: Circuit breakers are generally more space-efficient than fused switches, especially in distribution systems1.
Simplified coordination: Circuit breakers are easier to coordinate in a protection scheme, particularly for service disconnects1.
Convenience: Circuit breakers combine switching and protection functions in one device, offering automatic fault interruption2.
Long-term cost-effectiveness: While initially more expensive, circuit breakers can be more economical over time due to their reusability and lack of fuse replacement costs.
Adaptability: Circuit breakers can handle various fault conditions and are suitable for most applications, providing versatile protection.
However, it's important to note that fused disconnects may still be preferred in certain situations, such as:
Very high current applications, especially in industrial settings with high kVA transformers.
When equipment specifications require fuses.
In areas with extremely high fault currents, like New York City, where fuses may be more cost-effective for handling high fault currents.
The choice between fused disconnects and circuit breakers should be based on specific application requirements, local codes, and system characteristics.