“What do you mean we need to relabel the electrical equipment? Didn’t we just do this a few years ago?”
This is a pretty common response when addressing the requirements of NFPA 70E 130.5(2), which necessitate that the arc-flash risk assessment shall, “be updated when a major modification or renovation takes place. It shall be reviewed periodically, at intervals not to exceed 5 years, to account for changes in the electrical distribution system that could affect the results of the arc-flash risk assessment.”
What if, during the review process, you discover that some of the results changed? Do the labels need changing, too? This could become expensive.
NFPA 70E provides specific minimum requirements for labeling, which include listing the nominal system voltage and arc-flash boundary. For listing arc-rated clothing and personal protective equipment (PPE) requirements, the 2015 edition of NFPA 70E states that at least one of the following must be used:
• Available incident energy and working distance or the arc-flash PPE category
• Minimum arc rating of clothing
• Site-specific level of PPE
Here are a few ideas that may help avoid relabeling when a study is updated.
Arc rating only
Most companies use a specific arc rating (or two) for their arc-flash protection requirements. Often this is 8 or 12 calories per square centimeter (cal/cm2) for daily wear and 40 cal/cm2 for higher hazard areas. A simplified labeling method for defining the PPE requirements is to only list the arc rating. Do not include the calculated incident energy on the label.
This is contrary to current common practices, but it follows a similar logic that is used for short-circuit studies. In a traditional short-circuit study, the interrupting rating is listed on the equipment. The calculated short-circuit current is typically not listed unless required by National Electrical Code 110.24(A). The short-circuit study documents the analysis results and confirms the equipment’s interrupting/withstand ratings are adequate and where deficiencies may exist. This concept can easily be used for reviewing arc-flash risk assessments. List the arc rating on the label, and use the study to verify that the recommended arc rating is still adequate or where a higher arc rating is needed.
Although not required by NFPA 70E, it is a good idea to also include the working distance when listing the arc rating on the label. The arc rating is usually based on a calculated incident energy, which is a function of distance from the prospective arc. Without the working distance, the worker will not know if the arc rating is sufficient at 18 inches, 24 inches or some other distance.
Standardized arc-flash boundary
The arc-flash boundary varies at each location depending on the short circuit current, arc duration and many other important variables. Since the arc-flash boundary only affects the person that is not protected and not the person performing the work, you shouldn’t get caught up in the details of whether it is calculated as 2½ feet, 41/10 feet or another number. Just keep unprotected (and unqualified) people out of the way by using a large standardized minimum boundary. If possible, 8 feet, or perhaps 10, can be used, which makes the electrical safety practices much simpler and keeps unprotected people out of harm’s way.
The standardized boundary should be voltage-specific, i.e., one standardized boundary for low voltage and maybe a different one for medium voltage. This is because arc-flash boundaries tend to be larger at medium voltage.
The arc-flash risk assessment can be used to confirm where the large boundary is adequate and may point out where an even larger boundary may be necessary.
There may be some practical exceptions to this idea, such as an arc-flash boundary that really is small, which means using a large boundary would prohibit pedestrian traffic in the area.
Since the definition of the arc-flash boundary is the distance where the incident energy is 1.2 cal/cm2, it may be desirable to use a different term if the large standardized boundary method is used.
No new labels?
Using the simplified method of labeling can make updating or reviewing the arc-flash risk assessment much simpler. The study results can be used to confirm that the arc ratings and standardized boundaries are still adequate at each location. As long as the results of the new study don’t exceed the arc rating or larger standardized arc-flash boundaries on the existing label, there is no need to change the label.
But how would someone know if the labels are still adequate after there has been a new study? One method is to adhere a small sticker on the label confirming the arc-flash study was reviewed and the information on the label is still valid.
Although a date is not required on arc-flash labels, according to NFPA 70E, including a date on the original label and subsequent stickers can assist in determining when the five-year review requirement approaches.
About The Author
PHILLIPS, P.E., is founder of brainfiller.com and provides training globally. He is Vice-Chair of IEEE 1584 Arc Flash Working Group, International Chair of IEC TC78 Live Working Standards and Technical Committee Member of NFPA 70E. He can be reached at [email protected].