NFPA 70E uses the term “normal operation” to assess the risk of an arc flash hazard.

According to 2024 Edition of NFPA 70E 110.2(B) Exception No. 1: Normal operation of electric equipment is permitted where a normal operating condition exists. This requires that all of the following conditions are satisfied.

1. The equipment is properly installed

2. The equipment is properly maintained

3. The equipment is rated for the available fault current (NEW!)

4. The equipment is used in accordance with instructions included in the listing and labeling and in accordance with manufacturer’s instructions

5. The equipment doors are closed and secured

6. All equipment covers are in place and secured

7. There is no evidence of impending failure.

The concept of normal operation was originally introduced in response to another word: interaction. Before we go any further, let’s look at the history of the above seven conditions, why they are important and how they are used as part of an arc flash risk assessment. 

2009—Arc flash hazard and interaction

Prior to the 2009 edition of NFPA 70E, an arc flash hazard was considered to exist when there were exposed energized electrical conductors or circuit parts. However, the 2009 edition introduced the word “interaction” to address a possible increased risk of an arc flash when a person is interacting with the enclosed energized equipment in a way that could cause an electric arc. It further referenced that, under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard. And, thus, the confusion began. 

What does “interaction” mean? How can operating a switch result in an arc flash? What is a normal operating condition? 

The addition of 'equipment is rated for the available fault current' is important to avoid a potentially dangerous situation with inadequately rated electrical equipment.

A frequent response regarding interaction was, ”If someone interacts with equipment such as operating a switch, and the switch fails, and it creates a short circuit, and it results in an arc flash, and the doors blow open, and…” I quickly responded with: “Do you realize how many times you said ‘and?’” The more “ands” there are for an incident to occur, the lower the likelihood is. 

2015—List of conditions

The term “normal operation” remained a point of some confusion until the 2015 edition of 70E when a list of five conditions was introduced for clarification. A new Table 130.7(C)(15)(A)(a), Arc Flash Hazard Identification, was also added to determine whether arc flash PPE is required. The table lists tasks such as normal operation of a circuit breaker, switch, contractor or starter. Depending on the task and satisfying the conditions, the table is used to identify whether arc flash PPE is required. If all five conditions are satisfied, the table indicated no arc flash PPE is required. 

2018—Likelihood of occurrence

In the 2018 edition, “no evidence of impending failure” was added as a sixth condition. Also, Table 130.5(C), Estimate of the Likelihood of Occurrence of an Arc Flash Incident, was introduced, replacing the Arc Flash Hazard Identification Table. This listed whether there was a “likelihood of occurrence” of an arc flash based on the specific task and the equipment being in either a normal or abnormal condition. Normal condition requires satisfying all six conditions.

2024—Available fault current

A seventh condition was added to the 2024 edition: The equipment is rated for the available fault current. 

Isn’t this new condition already addressed if condition one is met?

Condition one states, “The equipment is properly installed,” which should mean the equipment is rated for the available fault current. The National Electrical Code requires equipment such as circuit breakers, panels, switchboards and others to have an interrupting rating at least equal to the available fault current. As part of the design and installation of the distribution system, a short-circuit study is often conducted based on data that includes the available fault current from the electric utility. 

However, electric utility fault current can increase as the utility infrastructure expands to meet increasing electrical demand. Additions such as new substations can increase the available fault current. Although a facility’s equipment might have been adequate when installed, it might not be years later if the utility short-circuit current increases. 

The addition of “equipment is rated for the available fault current” is important to avoid a potentially dangerous situation with inadequately rated electrical equipment.

It’s been a 16-year journey, but “normal operating condition” is much clearer than it was in 2009.

Note: This column is based on the author’s views and experience.