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Code Q&A: NEC Requirement for Panelboards

May 23, 2024
Test your knowledge of the NEC with this challenging question.

Courtesy of Based on the 2023 NEC.

Question: Panelboards supplied by a 3-phase, 4-wire, delta-connected system shall have the phase with the higher voltage-to-ground connected to the _____ phase.

a) A

b) B

c) C

d) any of these

See answer below.





Answer: b) B

According to Sec. 408.3(E)(1), "The B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems."

These materials are provided by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (, one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.

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