Electrical Troubleshooting Quiz — Nov. 6, 2018
The plant has been experiencing nuisance tripping of circuit breakers. Sometimes it’s a feeder breaker, sometimes it’s a branch circuit breaker. The procedure for addressing these trips is:
- Use a DMM to check the load side terminals for a short in the connected load.
- Disconnect all loads, and visually inspect each one.
- Where practical, perform insulation resistance testing on the circuit conductors.
- If no problems are found, close the breaker. Reconnect each load one at a time.
- Perform voltage and current checks with loads connected.
Only rarely have any problems been found. Adding to the frustration, the nuisance trips repeat in the same areas of the plant even though the breaker trip reset procedure has been repeatedly performed. How can you solve this?
You don’t want your feeder breakers serving as “backup protection” for any of your branch circuit breakers. It sounds like this is one thing that’s going on, so a coordination study is needed. Also, a determination of the correct breaker for a given circuit must be made (based on load characteristics) along with a determination of the settings for each breaker.
The trip response procedure is better than what’s typical, but a DMM operates on 9V and your feeders operate at 480V. There may be system defects that neither the DMM nor the insulation resistance tester can identify. Consult with a qualified testing firm.
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.