Maintenance, Repair & Operations

NEC Rules for Flexible Cords and Cables for Audio Signal Processing Equipment

March 5, 2019

Understanding Article 640 of the 2017 NEC

Article 640 of the 2017 NEC provides different requirements for permanent installations of this equipment (Part II) than it does for installing portable versions (Part III). One of several places we can see that is in the requirements for flexible cords and cables [Sec. 640.21 and Sec. 640.42].

For flexible cords and cables between equipment and branch-circuit power, the requirements are identical [Sec. 640.21(A) and Sec. 640.42(A)]. But between loudspeakers and amplifiers or between loudspeakers:

Permanent [Sec. 640.21(B)]: Cables must comply with Art. 725.
Portable [Sec. 640.42(B)]: Cables must comply with Part I of Art. 400 and Parts I, II, and III of Art. 725. Cords and cables listed for portable use must be hard or extra-hard service per Art. 400.

The next subsection [Sec. 640.21(C) and Sec. 640.42(C)] has a similar difference in the requirements, and 640.21(C) is just for “between equipment” while 640.42(C) is for “between equipment and/or between equipment racks.”

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.