Test & Measurement

Tip of the Week: Avoid the “Just Drive Another Ground Rod” Solution

Dec. 19, 2016

Driving ground rods into the floor will not prevent equipment losses caused by transient voltage damage.

From all indications, some recent equipment losses are due to transient voltage damage. How should you respond?

Often, the “solution” is to drive ground rods everywhere. A motor failed, no problem; we prevent that by driving a ground rod through our nice factory floor and bolting it up. The sad truth is that this response accomplishes nothing. The soil resistivity is just too high to create an effective low impedance path back to the source.

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Another “solution” is to install surge protection at the service. This will, if properly designed, reduce incoming surges, but it does not protect against the most common source of high voltage transients. That source is equipment inside the plant. A typical culprit is a large motor that starts across the line. A good solution for that problem is to install a soft start for that motor.

Soft starts on large motors may not stop all sources of load side transients, however. If that’s your situation, then a surge suppression system is needed. But consider your system carefully, understanding that a given surge device will reduce the transient voltage only so much. Think of a series of voltage reductions, and design a tiered system accordingly.

And, yes, of course you want to ensure all non-current-carrying metallic objects are bonded as required by Art. 250, Part V of the National Electrical Code (NEC).

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.