The National Electrical Code (NEC) is an installation code. As stated in the scope of Article 90, the NEC covers the installation of electrical conductors, equipment and raceways; signaling and communications conductors, equipment and raceways; and optical fiber cables and raceways [90.2(A)]. Some of the locations and installation required to comply with the NEC include public and private premises, yards, parking lots and installations of conductors and equipment that connect to the electricity supply. For a complete list of locations required to comply with provisions in the NEC, see 90.2(A)(1) through (4). 


Locations and installations not required to comply with NEC requirements are listed in 90.2(B)(1) through (5). As stated in 90.1(B), the NEC contains provisions that are considered necessary for safety. The second sentence states compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient or adequate for good service or future expansion of electrical use. 


All of the requirements in the NEC are there for one reason, and that is the “practical safeguarding of persons and property from hazards arising from electricity use” [90.1(A)]. Keeping people and property safe from such hazards has been the intent of the NEC since its inception. 


In addition to the purpose and scope, Article 90 contains other sections that are essential to understanding the rest of the Code book. Other sections include Code arrangement, mandatory rules, permissive rules, explanatory material and units of measurement.


Article 110 in Chapter 1 covers general requirements for electrical installations. The arc flash hazard-warning requirement in 110.16 is the first requirement in the Code for marking or labeling on electrical equipment. Section 110.15 also mentions marking, but it pertains to the marking of the high-leg conductor or busbar. Section 110.16 pertains to electrical equipment such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures and motor control centers.


Because “such as” precedes the list of electrical equipment in 110.16, it is not all-inclusive. So, how do we determine which electrical equipment shall be labeled in accordance with this section? The last part of the sentence provides the answer. If the electrical equipment is likely to require examination, adjustment, servicing or maintenance while energized, the Code requires the arc flash hazard warning.


As the first sentence states, this requirement does not apply to electrical equipment in dwelling units. The marking or labeling required by 110.16 is intended to warn qualified people of potential arc flash hazards. Other than the labeling or marking being a warning to qualified people, there is no mention of the wording required on the label. One warning label may state, “Warning, Arc Flash and Shock Hazard. Appropriate PPE Required.” Another warning label may have fewer words by stating, “Warning, Arc Flash and Shock Hazard.” Since the label or marking is intended to warn qualified people of potential arc flash hazards, the label could simply read “Warning, Arc Flash Hazard” (see Figure 1).


The 2014 NEC introduced some changes to 110.16. The first change added the term “switchgear” to the list of electrical equipment this section covers. As a global change, the term was added to this section and other sections throughout the Code.


Another change was made to where the warning label shall be applied to the electrical equipment—at the factory or in the field. Before the 2014 edition, this section stated that the electrical equipment had to be field-marked with the arc flash warning label. Now, this section states that the warning label can be applied in the field or at the factory. Since the NEC only requires a basic warning label at this time, it does not matter where the label is applied. The last sentence in 110.16 states that the marking shall meet the requirements in 110.21(B) and shall be located so as to be clearly visible to qualified people before equipment examination, adjustment, service or maintenance. 


Section 110.21(B) is new in the 2014 edition. It pertains to caution, warning or danger signs or labels required by the NEC. In accordance with 110.21(B), the marking or label shall: 1) adequately warn of the hazard using effective words and/or colors and/or symbols, 2) be permanently affixed to the equipment or wiring method and shall not be handwritten, and 3) be of sufficient durability to withstand the environment involved (see Figure 2).


The first informational note under 110.16 mentions NFPA 70E. As stated in 90.1 of 70E, the purpose is to provide a practical, safe working area for employees relative to the hazards arising from electricity use. The informational note states that 70E provides guidance, such as determining the severity of potential exposure, planning safe work practices, arc flash labeling and selecting personal protective equipment (PPE). Requirements in the NEC are intended for use primarily by those who design, install and inspect electrical installations. The provisions in 70E are similar to the Occupational Safety and Health Administration’s (OSHA) electrical regulations in that they address employers and employees in their workplaces. Provisions in 70E are intended to provide protection to the employee from electrical hazards. The 70E standard addresses electrical safety-related work practices, safety-related maintenance requirements, and other administrative controls for employee workplaces that are necessary for the practical safeguarding of employees relative to the hazards associated with electrical energy during activities such as the installation, inspection, operation, maintenance, and demolition of electrical conductors, electrical equipment, signaling and communications conductors and equipment, and raceways [90.2(A) in 70E].


NFPA 70E also has an equipment-labeling provision. As stated in 70E, 130.5(D), electrical equipment such as switchboards, panelboards, industrial control panels, meter socket enclosures, and motor control centers that are in other than dwelling units and that are likely to require examination, adjustment, service or maintenance while energized, shall be field-marked with a label containing all of the information in 130.5(D)(1) through (3). 


The information on the equipment label required by 70E is vastly different from the information required by the NEC. In accordance with 110.16, the warning could be as basic as “Warning, Arc Flash Hazard.” Information on the equipment label required by 70E is far from basic. The first item required by 70E is nominal system voltage of the equipment, and the second item is the arc flash boundary. The third item required by 70E provides options. 


In accordance with 130.5(D)(3), at least one item in 130.5(D)(3)a through 130.5(D)(3)c shall be on the equipment label. Although there are only three letters (a though c), there are actually four options. The first of the three items contains two options: 1) available incident energy and the corresponding working distance, or 2) the arc flash PPE category in Table 130.7(C)(15)(A)(b) or Table 130.7(C)(15)(B) for the equipment.


With the first part of this option, it is permissible to put either the available incident energy and the corresponding working distance on the equipment label or the arc flash PPE category in Table 130.7(C)(15)(A)(b) or Table 130.7(C)(15)(B) for the equipment on the label. This section in 70E clearly states that it is not permissible to put both of these two options on the same piece of equipment (see Figure 3).


The second item (the third option) in 130.5(D)(3) is the minimum arc rating of clothing required for the equipment. The third item (the fourth option) in 130.5(D)(3) is site-specific level of PPE. Although it is not required, some labels show the limited approach boundary and the restricted approach boundary. For the complete equipment-labeling requirement in NFPA 70E, see 130.5(D).


Next month’s column continues the discussion of requirements for electrical installations.