Electrical Troubleshooting Quiz — Dec. 3, 2019
An 800A molded-case circuit breaker that feeds a critical area of the plant started having nuisance trips. The first few times, maintenance would look for obvious problems and perform testing to verify no circuits were faulted to ground. Then, they would reset the breaker. After a while, they stopped performing testing and would just reset the breaker.
This is the plant electrical engineer's first job since graduating, and his education had not prepared him for what to do in this case. The senior electrician said there was a spare breaker in the stockroom, so they should just replace the one that is nuisance tripping.
That's what they did, but the problem persisted. What should they do now?
That's an expensive item to simply replace. And what is the condition of the one that was in the stockroom? Was that spare regularly maintained? At least lubricated and tested? Or was it simply assumed to be in serviceable condition? It's possible both breakers are bad.
It's also possible that something real is causing the breaker to trip. Get a thermographic image of the breaker now in service, perhaps multiple times. Next, connect a power analyzer so you can see what's going on both upstream and downstream of that unit. Leave it connected long enough to capture the next nuisance trip.
Contact a qualified electrical testing firm to test the original breaker. If they deem the breaker serviceable, have them perform the factory required maintenance on that breaker. Now you have a known good breaker. Schedule downtime to install it.
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.