Code Quiz: Defining Ampacity

Sept. 11, 2019

How much do you know about ampacity?

Question: What is ampacity, as applied to conductors?

See the answer below.

Answer: Ampacity is the maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating (NEC Art. 100).

Explanation: Most everyone typically answers, "How much current a conductor can carry." While this is true it is only part of the answer. A conductor must carry the current continuously and in the conditions it is being used in. It must also carry the current without overheating. For these reasons the ampacity of a conductor is subject to adjustments in Sec. 310.15.

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.