A 3/0 AWG copper feeder conductor is tapped with 20 feet of 2 AWG conductor. What is the maximum OCPD size allowed at the termination of the tap conductors installed in a fused switch or circuit breaker? (ALL conductors and terminations are rated 75°C.)

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Multiple Choice

A 3/0 AWG copper feeder conductor is tapped with 20 feet of 2 AWG conductor. What is the maximum OCPD size allowed at the termination of the tap conductors installed in a fused switch or circuit breaker? (ALL conductors and terminations are rated 75°C.)

Explanation:
Taps must be protected by an overcurrent device sized to protect the tap conductors, not the feeder. In this case, the tap conductor is 2 AWG copper, rated 75°C. The ampacity of 2 AWG copper at 75°C is 115 A. Therefore, the OCPD at the termination of the tap cannot exceed 115 A. The largest standard breaker or fuse rating at or below 115 A is 110 A, making 110 A the maximum allowed. The other options either exceed the tap conductor’s ampacity (125 A, 150 A) or are not the largest that fits (100 A).

Taps must be protected by an overcurrent device sized to protect the tap conductors, not the feeder. In this case, the tap conductor is 2 AWG copper, rated 75°C. The ampacity of 2 AWG copper at 75°C is 115 A. Therefore, the OCPD at the termination of the tap cannot exceed 115 A. The largest standard breaker or fuse rating at or below 115 A is 110 A, making 110 A the maximum allowed. The other options either exceed the tap conductor’s ampacity (125 A, 150 A) or are not the largest that fits (100 A).

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