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Code Quiz: Determining the Appropriate Conductor Ampacity

May 4, 2022

Test your knowledge of the NEC with this challenging question.

Based on the 2020 NEC.

Question: How do you determine the ampacity of the conductors serving a three-phase 480V motor?

See answer below.

Answer: By using the value given in Table 430.250

Explanation: Section 430.6(A)(1) of the 2020 NEC requires you to use the values shown in Table 430.250 instead of the value on the motor nameplate.

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.