Code Quiz: Motor Conductor Calculations

Aug. 5, 2021

Test your Code knowledge.

Based on the 2020 NEC.

Question: What is the minimum ampacity for a conductor supplying a 480V 10 HP motor with a nameplate current of 13A?

See answer below.

Answer: 17.5A

Explanation: Section 430.6(A)(1) requires the current value for sizing conductors to be based on Table 430.250. For the motor listed above, the value would be 14A. Section 430.22 requires this value to be multiplied by 125%.

14A x 125% = 17.5A

Lupacchino is a senior design engineer with Gaylor Electric, Inc. in Noblesville, Ind. and serves as an alternate on NEC Code-Making Panel No. 3. He is currently licensed in more than 80 jurisdictions. He can be reached at [email protected].

About the Author

John Lupacchino | Senior Design Engineer

John began his career in electrical construction as an apprentice and worked his way through the trade. He is currently licensed in more than 80 jurisdictions. With more than 35 years of experience, he now plays a vital role in Gaylor Electric’s Engineering Department, where he serves as a senior design engineer. With a focus on design engineering, quality assurance, and code compliance, he has earned the highest level of respect from industry professionals alike. John currently serves as an alternate on NFPA 70 Code Making Panel No. 3. In addition, he enjoys sharing his electrical knowledge through education. As an Associated Builders and Contractors instructor, he continues to help grow a new generation of high-performing construction leaders.