Maintenance, Repair & Operations

NEC Requirements for Sensitive Electronic Equipment

April 16, 2019

A quick look at NEC Art. 647

Article 647 of the 2017 National Electrical Code (NEC) provides the requirements for “sensitive electronic equipment” but does not define the term. Nor is there a definition in Art. 100.

But isn’t all electronic equipment sensitive by its very nature? After all, there’s a reason we use static discharge protection when working on circuit boards but don’t use it when working on premises wiring circuits.

One way to solve this little mystery is to go through old editions of the NEC. A version of this material was originally included in an Article that provided the requirements for audio and video production equipment. Its focus was on reducing the electrical noise that can interfere with that equipment.

One of the unsafe practices aimed at reducing noise was to install a “separate” grounding system. Anyone examining the installation with an awareness of Kirchhoff’s Law of Parallel circuits would readily surmise that it created dangerous differences of potential. It was a cure worse than the disease. Article 647 addresses noise reduction practices, including tighter limits on voltage drop.

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.