You've been interacting with a piece of equipment for years, now you've had an arc flash evaluation and a sticker says "6.1 cal/cm^2". Should you "suit up" to turn this equipment on or off?
The answer depends on your risk. Consider NFPA 70E® 2024 - Table 130.5(C) Estimate of the Likelihood of Occurrence of an Arc Flash Incident for ac and dc. Using this table, you find your task, consider it's Operating Condition and then read the Likelihood of Occurrence
Here's an example: Operation of a CB, switch, contactor, or starter:
- if the Operating Condition is "Normal" then there is no Likelihood of Occurrence
- if the Operating Condition is "Abnormal" then, yes there is a Likelihood of Occurrence
What is normal? For this we refer to NFPA 70E® 2024 - 110.2(B)
Exception No. 1: Normal operation of electric equipment shall be permitted where a normal operating condition exists. A normal operating condition exists when 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
(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
Informational Note No. 1: The phrase properly installed means that the equipment is installed in accordance with applicable industry codes and standards and the manufacturer's recommendations. The phrase properly maintained means that the equipment has been maintained in accordance with the manufacturer’s recommendations and applicable industry codes and standards. The phrase evidence of impending failure means that there is evidence such as arcing, overheating, loose or bound equipment parts, le damage, deterioration, or water damage
What is considered abnormal? Examples beyond not meeting the criteria for "normal" include a tripped breaker. If you lost power because a breaker tripped, then you are no longer normal. Turning the breaker back on would have an increased Likelihood of Occurrence and would constitute wearing appropriate arc flash PPE.
Table 130.5(C) states that Operating of a CB or switch the first time after installation or completion of maintenance in the equipment, in any condition, will always have a likelihood of occurrence of an arc flash incident.
To summarize, if you are performing work on something that has a likelihood of occurrence of an arc flash incident, then you should suit up to the level of protection indicated on your arc flash hazard label.
We also have a good post regarding high arc flash values (https://www.70econsultants.com/blast-pressure-above-40-cal-cm2/) as well as a post about arc flash around low voltages (https://www.70econsultants.com/arc-flash-and-shock-hazards-for-120vac-and-208vac/)
To view Table 130.5(C) you can click on the following link, then scroll to "View Free Access" (you will need to login with a free account). https://www.nfpa.org/codes-and-standards/nfpa-70e-standard-development/70e
