NFPA 70E: Annex Marks the Spot —Part 14

May 16, 2025

Does your facility owner understand the employee safety-related concepts to apply to the facility’s electrical system?

Annex O addresses the responsibilities of the facility owner or party with similar control to perform a risk assessment during the design of electrical systems and electrical installations. It covers employee safety-related design concepts, but not specific design requirements.

These concepts are laid out in Section O.2, which consists of these subsections:

O.2.1. Essentially, the facility owner or party with similar control should perform a risk assessment during the design of electrical systems and electrical installations

O.2.2. Design options should help reduce risk by three enumerated means. For example, by reducing the likelihood of exposure.

O.2.3. This presents a list of nine incident energy reduction methods that have proven to be effective. One of those is differential relaying and another is using an arc flash relay. A differential relay compares the current flowing into protected equipment to the current flowing out of it. If there’s a difference (thus the name differential), a fault must exist within this equipment. The relay can be set for a fast interruption. An arc flash relay senses light and if the light is beyond a certain level, as it would be with an arc flash, the relay trips the upstream overcurrent protection device.

O.2.4. This lists thirteen additional “safety by design” methods. One of those is the installation of inspection windows for non-contact inspections such as thermal imaging. This eliminates the need to open doors or remove covers to perform those inspections, thus saving time while reducing risk. Contact your switchgear manufacturer for your options with these. Another is installing provisions for remote opening and closing of circuit breakers and switches. This should be done in a way that puts the employee outside the arc flash boundary.

Annex O is a wealth of information for designing out dangers. By designing out dangers, you reduce the cost of safety while increasing safety. You reduce the risk and/or severity of production interruptions. You may even get a discount on your insurance, but if not you will at least reduce the risk of burning down your facility.

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.