A branch circuit, where 2 AWG conductors are installed, serves a single load that will not operate more than 3 hours. The equipment served by the branch circuit is marked for conductors larger than 1 AWG. These conductors can be protected by a circuit breaker with a rating no greater than ___ amps.

A branch circuit, where 2 AWG conductors are installed, serves a single load that will not operate more than 3 hours. The equipment served by the branch circuit is marked for conductors larger than 1 AWG. These conductors can be protected by a circuit breaker with a rating no greater than ___ amps.

• A. 150
• B. 100
• C. 110
• D. 125

Answer: (D)

The main idea is to size the overcurrent protection to the actual capacity of the conductors, taking into account the conductor’s temperature rating and whether the load is continuous. With 2 AWG conductors, you look at the ampacity for the conductor size at the appropriate insulation rating. If the equipment is marked for conductors larger than 1 AWG, that indicates it can accept conductors with a higher temperature rating (often 90°C) and you can use the higher ampacity rating for the conductor. For copper 2 AWG with 90°C insulation, the ampacity is about 130 A. The overcurrent protective device must not exceed that conductor ampacity, and it should be a standard breaker rating that fits below or at that value. The largest standard breaker size not exceeding 130 A is 125 A. Since the load is not operating for more than 3 hours, it’s not considered a continuous load, so the 125% continuous-load adjustment does not apply here. Therefore, the correct protection rating is 125 A.

The main idea is to size the overcurrent protection to the actual capacity of the conductors, taking into account the conductor’s temperature rating and whether the load is continuous.

With 2 AWG conductors, you look at the ampacity for the conductor size at the appropriate insulation rating. If the equipment is marked for conductors larger than 1 AWG, that indicates it can accept conductors with a higher temperature rating (often 90°C) and you can use the higher ampacity rating for the conductor. For copper 2 AWG with 90°C insulation, the ampacity is about 130 A. The overcurrent protective device must not exceed that conductor ampacity, and it should be a standard breaker rating that fits below or at that value. The largest standard breaker size not exceeding 130 A is 125 A.

Since the load is not operating for more than 3 hours, it’s not considered a continuous load, so the 125% continuous-load adjustment does not apply here. Therefore, the correct protection rating is 125 A.