Is it true that the maximum rating or setting of overcurrent protection for transformers under 1,000 volts per 450.3 is different for circuit breakers compared to fuses?

Is it true that the maximum rating or setting of overcurrent protection for transformers under 1,000 volts per 450.3 is different for circuit breakers compared to fuses?

• A. True
• B. False
• C. Not specified
• D. Both

Answer: (B)

The main idea is that NEC 450.3 sets a single maximum overcurrent protection rating or setting for transformers under 1,000 volts based on the transformer's primary current. That upper limit applies regardless of whether you’re using a fuse or a circuit breaker. The code doesn’t assign different maximums to protect with a fuse versus a breaker; it provides the same ceiling for both device types, while the choice between fuse and breaker is guided by other considerations (such as interrupting rating, coordination, and installation requirements). So the statement that the maximum OCPD rating or setting differs between circuit breakers and fuses is not correct.

The main idea is that NEC 450.3 sets a single maximum overcurrent protection rating or setting for transformers under 1,000 volts based on the transformer's primary current. That upper limit applies regardless of whether you’re using a fuse or a circuit breaker. The code doesn’t assign different maximums to protect with a fuse versus a breaker; it provides the same ceiling for both device types, while the choice between fuse and breaker is guided by other considerations (such as interrupting rating, coordination, and installation requirements). So the statement that the maximum OCPD rating or setting differs between circuit breakers and fuses is not correct.