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National Electrical Code

NEC Requirements for Art. 725, Circuits — Part 2

Oct. 6, 2020

An overview of Class 1 remote-control, signaling, and power-limited circuits

A Class 1 circuit is that portion of the wiring system between the load side of the overcurrent device (or power-limited supply) and the connected equipment [100]. Article 725 of the National Electrical Code provides the requirements for Class 1 remote-control, signaling, and power-limited circuits in Part II. Highlights include:

Circuits supplied from a source with a max output of 30V and 1000A are “power-limited” [725.41(A)].
Class 1 circuits that are not power-limited cannot exceed 600V (no power limit on the source) [725.41(B)].
For Class 1 circuits with conductors 14 AWG or larger, you cannot use the ampacity correction factors of 310.14 in the ampacity calculations for overcurrent protection [725.43].
You must install Class 1 conductors per the requirements of Part 1 of Art. 300 and the appropriate article(s) in Chapter 3.
If you run two or more Class 1 circuits in the same cable, cable tray, enclosure, or raceway, then you can mix AC and DC. However, that is true only if all conductors are insulated for the maximum voltage of any conductor in the cable tray, enclosure, or raceway [725.48(A)].

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.