• Article 110 General Requirements for Electrical Installations
• Section 110.16 Arc-Flash Hazard Warning

Two types of labeling are required as part of 110.16(A) and 110.16(B). Section 110.16(A) has been a part of the NEC since 2002, requiring that electrical equipment, such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers, in other than dwelling units and likely to require examination, adjustment, servicing, or maintenance while energized, be field or factory marked to warn qualified persons of potential electric arc flash hazards. This marking is very generic in nature to make the electrical worker aware of a potential hazard and quite often is shipped on the equipment from the manufacturer.

Section 110.16(B) was introduced as part of the 2017 NEC with the intent to provide information on the equipment for the electrical worker to determine the level of PPE required when justified energized work is performed. This section requires service equipment and feeder-supplied equipment to have a permanent arc flash label that is field or factory applied to service equipment and feeder-supplied equipment rated 1000 A or more. The language is clear to point the user of Code to acceptable industry practices. The label must also include the date the label was applied. NFPA 70E is a well-recognized industry resource for proper arc flash labeling on equipment.

The 2023 NEC addressed three areas of concern for the arc flash labeling of this equipment.  

1. First and foremost was the concern that the previous language that included marking of voltage, available fault current, and clearing of the service overcurrent protective devices (OCPDs) was misleading and could cause an electrical worker to not dress appropriately with the proper PPE. Service equipment arc flash values are dependent upon the clearing time of the upstream OCPD, which in many cases is the OCPD on the line side of the utility transformer, resulting in a very high incident energy at this equipment.

2. The previous rule of equipment rated 1200 A and higher was reduced to 1000 A and higher. Incident energy is a known problem for electrical distribution equipment and this change recognizes the need to require an arc flash label for equipment rated 1000 A and higher.

3. Finally, the next change recognizes that arc flash labeling should not only be required for service equipment but also feeder equipment. NEC 2023 expanded the requirement to 
feeder-supplied equipment rated 1000 A and higher requiring arc flash labeling further down into the power distribution system. It is recognized that the impacted equipment of incident energy is not just service equipment rated 1000 A and higher but also feeder-supplied equipment rated 1000 A and higher.

Requirements in the 2024 NEC® arc flash labeling