One of the most common compliance mistakes facilities make is conducting an arc flash study once — then treating it as permanently valid. This is not how NFPA 70E works, and relying on outdated arc flash data can be just as dangerous as having no study at all. Here is exactly what the standard requires, and why the answer matters more than most people expect.
What NFPA 70E Actually Says
NFPA 70E Article 130.5 requires that an Arc Flash Risk Assessment be reviewed and updated at intervals not to exceed five years. This is a maximum interval — not a recommended one. The standard also requires an immediate update whenever major modifications or renovations occur to the electrical system, or when protective device settings change.
What counts as a major modification? Adding or removing electrical equipment, changing transformer sizes, installing new protective devices, modifying overcurrent protection settings, or reconfiguring system topology. In practice, most active facilities experience at least one of these changes within a five-year window — making more frequent reviews the norm, not the exception.
Why Outdated Studies Create Real Danger
An arc flash study is only accurate for the electrical system it was modeled on. When your system changes, the incident energy levels and arc flash boundaries change too. A worker relying on PPE guidance from a six-year-old study may be significantly underprotected for the actual hazard they face today.
Consider a scenario where a facility has upgraded its main transformer since the last study. A larger transformer delivers higher fault current — which can dramatically increase incident energy at downstream equipment. The old labels on those panels are now inaccurate and potentially life-threatening.
Triggers That Should Prompt an Immediate Review
- Installation of new generators, transformers, or switchgear
- Changes to protective relay or breaker settings
- Addition of new electrical distribution feeders
- Facility expansions or significant equipment additions
- Acquisition of a new facility or building
- Discovery that previous study data was incorrect or incomplete
How to Stay Ahead of the Five-Year Requirement
The most effective approach is to embed arc flash study reviews into your standard change management process. Any time a significant electrical modification is proposed, the review requirement should be part of the project scope. This eliminates the risk of the five-year clock running out unnoticed and ensures your labels and PPE guidance reflect the actual system at all times.
Bowtie Engineering can conduct initial studies, periodic reviews, and update studies following system changes, ensuring your facility remains continuously compliant.
Learn more about Bowtie’s Arc Flash and Incident Energy Study services, or review how our Electrical Maintenance program keeps your system data current year-round.