A feeder tap less than 25 feet long does not require overcurrent protection at the tap if the Ampacity of the tap conductor is at least?

• A. 40% of the feeder conductor
• B. 33 1/3 % of the feeder conductor
• C. 20% of the feeder conductor
• D. 50% of the feeder conductor

Answer: (B)

The principle at work is the feeder-tap protection rule. When a feeder tap is shorter than 25 feet, you don’t need overcurrent protection at the tap as long as the tap conductor’s ampacity is large enough relative to the feeder conductor. The required minimum is one-third (33 1/3%) of the feeder conductor’s ampacity. This ensures the tap can safely carry its share of current without overheating during normal operation, while the upstream feeder protection will still clear a fault on the feeder. For example, if the feeder is rated for 100 A, the tap conductor must have an ampacity of at least 33 A to avoid adding a protection device at the tap; anything less would require protection at the tap. The other percentages don’t meet this NEC threshold, so they aren’t the correct criterion.