Code Quiz: Conductors in Parallel

Aug. 7, 2019

Learn the NEC requirements for paralleling feeder conductors.

Question: What are the rules for paralleling feeder conductors?

See the answer below.

Answer: Section 310.10(H) of the 2017 NEC states the conductors for each phase, polarity, neutral, or grounded circuit shall be permitted to be connected in parallel with the following restrictions:

Conductors are 1/0 or larger
Conductors are the same length
Conductors are the same material
Conductors are the same size
Conductors have the same insulation type
Conductors are terminated in the same manner
When in separate cables or raceways the cables or raceways with conductors shall have the same number of conductors and have the same electrical characteristics

Explanation: These rules are meant to ensure each conductor in a paralleled set carries the same amount of current as the other conductors of the paralleled set.

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.