NEC General Requirements for Branch Circuits, Part 2
Article 210 provides the requirements for branch circuits. As with most NEC articles, it has its own general requirements. Like the arrangement in many articles, those consist of Part I. Section 210.5 provides requirements for the identification of branch circuits.
It starts off with A, B, C: grounded conductor, equipment grounding conductor, and ungrounded conductors. It makes short work of the first two:
- Identify the grounded conductor per Sec. 210.7 [Sec. 210.5(A)].
- Identify the equipment grounding conductor per Sec. 250.119 [Sec. 210.5(B)].
Not so short when it comes to the identification requirements of ungrounded conductors. It considers three types:
- Branch circuits supplied from one nominal voltage system.
- Branch circuits supplied from more than one nominal voltage system.
- Branch circuits supplied from DC systems.
Let’s look at each of these in order.
Branch circuits supplied from one nominal voltage system must be identified per Sec. 310.6(A)(3) [Sec. 210.5(C)(1)]. That has a lot of text that boils down into “make it clear they are not grounded or grounding conductors.”
If you have more than one nominal voltage system, that rule also applies. In addition, you have to identify each ungrounded conductor of a branch circuit by phase (or line) and nominal voltage at each termination, connection, and splice. You also have to document the method in a manner that is readily accessible or permanently post this information at each branch-circuit panelboard or similar branch-circuit distribution equipment. The exception to this rule is when you have an existing voltage system and then add a new one; you need to mark only the new one. By default, the other one is marked by not being marked but you still have to include these words on the new system label: “Other unidentified systems exist on the premises” [Sec. 210.5(C)(2)].
If you have branch circuits supplied by DC system operating at more than 60V, you have to mark each ungrounded conductor that is 4 AWG or larger with its polarity at each termination, connection, and splice [Sec. 210.5(C)(3)]. For ungrounded conductors that are 6 AWG or smaller, you have to use one of the identification means listed in Sec. 210.5(C)(3)(a) for the positive (for example, a continuous red outer finish) and one of the identification means listed in Sec. 210.5(C)(3)(b) for the negative (for example, a continuous black outer finish).
About the Author
Mark LamendolaMark 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.