Test & Measurement

Tip of the Week: Insights from NEC Article 90, Part 4

Aug. 28, 2017

What some refer to as requirements in the code may be merely informational notes for explanatory purposes.

You’ve probably heard someone talk about the NEC’s voltage drop requirement. One problem — the NEC does not have such a requirement (except for sensitive equipment, Art. 647). What people are referring to when they cite the "requirement" is one of two Informational Notes. These follow Sec. 210.19(A) and Sec. 310.15(A).

They aren’t requirements. They are “explanatory material.” You can see a full explanation in Sec. 90.5. There, you’ll also find the definitions of mandatory rules, permissive rules, and Informative Annexes. In short:

Mandatory rules identify actions that must be taken or that are prohibited. When you see “shall” or “shall not,” you are looking at one of these rules.
Permissive rules identify actions that are allowed but not required. To spot them, just look for “shall be permitted” or “shall not be required.”
Explanatory material is visually set apart from the Code requirements. For example, Informational Notes have a different font and are left-indented. And where you see brackets containing a reference to another document, that reference is for information purposes only.
The Informative Annexes at the back of the NEC contain non-mandatory information of the “must read” variety. You’re not actually required to read these, but if you want a high level of Code competence you won’t pass up the opportunity. Time spent poring over these is time well spent.

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.