110.16 Arc-Flash Hazard Warning

Section 110.16 became a part of the NEC with its introduction into the 2002 version of the NEC. The goal of the submitter was not directly achieved with the new requirements of 110.16 as the Code making panel debated and arrived at the marking of a hazard warning in this section instead of an actual arc flash label which was being sought by the submitter.  The submitter was working to achieve a marking of incident energy.  Keep in mind that this was the same year that IEEE 1584, “Guide for Performing Arc-Flash Hazard Calculations”, was published.  The substantiation used during that code cycle noted that “Significant number of electricians are being seriously burned and often killed from an accidental electrical flash while working equipment ‘hot’. Most of these serious accidents can be eliminated or significantly reduced if the electricians wear the proper type of protective clothing.  If switchboards, panelboards, loadcenters, and motor control centers were individually marked with the incident energy, the personnel would easily know what type of protective clothing to wear, because its rating is based upon the available incident energy in calories per square centimeter.[1]  

This section is divided into two first level subdivisions as follows:

(A) General

The requirement in (A) is for a general marking that an electrical hazard exists.  This label must be applied as follows:

Electrical equipment included:  Switchboards, switchgear, enclosed panelboards, industrial control panels, meter socket enclosures, and motor control centers

Where:  Other than dwelling units

Conditions:  Equipment that is likely to require examination, adjustment, servicing, or maintenance while energized

What:  Field or factory marking that warns qualified persons of potential electric arc flash hazards. 

These markings must meet the requirements in 110.21(B) and must be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.

(B) Service Equipment and Feeder Supplied Equipment

This section requires an actual arc flash label to be placed on service equipment and feeder supplied equipment that is rated 1000A and above.  The arc flash label must be in accordance with industry practice.  Incident energy labels are required by NFPA 70E for all equipment but this section of NFPA 70 is the only requirement that gets adopted by local jurisdictions. Industry references for this label include ANSI Z535.4 and NFPA 70E as well as IEEE 1584. This requirement clearly identifies that this is an Arc Flash label.

The NFPA 70E is the most frequently used reference for this type of label.  NFPA 70E Section 130.5(H) titled “Equipment Labeling” is the reference for this label.  This section of 70E requires the following be contained on a label:

  • Nominal system voltage
  • Arc flash boundary
  • At least one of the following:
    • Available incident energy and the corresponding working distance, or the arc flash PPE category in Table 130.7(C)(15)(a) or Table 130.7(C)(15)(b) for the equipment, but not both
    • Minimum arc rating of clothing
    • Site-specific level of PPE

Note that the language of 110.16 does include the date be a part of this label but the requirements of NFPA 70E do NOT.  Simply following the requirements of 130.5(H) would not be enough to meet the requirements of the NEC as the date must also be included on the label.

This label would meet the requirements of NFPA 70-2023 as it includes the date that the label was applied and meets the requirements of NFPA 70E.

NFPA 70-2023 Changes

110.16(B) which used to only focus on service equipment is now expanded to include feeder equipment.  In addition, the equipment rating has been lowered from 1200A or more to 1000A or more so as to expand arc flash labeling requirements for electrical worker safety.  The list of data required for the label that was previously included in this first level sub-division has been removed as a reference to applicable industry practice and captures proper labeling for this equipment.  The informational notes point the user of the Code to ANSI Z535.4 and NFPA 70E for more information on the label.

The phrase “arc flash” was added to clarify the type of permanent label required. 

The existing Informational Note No. 1 was deleted as it was considered redundant to the information contained in the remaining Informational Notes.

The contents of the label are now driven by the reference document used for calculating the incident energy. Previous language of this section in the NEC tried to align with the table method and calculation method highlighted in NFPA 70E Section 130.7(C)(15) and Section 130.5(G) respectively but the oversimplification of the label left technical inaccuracies that are now resolved.  

This label meets the requirements of 110.16(B) of NFPA 70-2020 but not NFPA 70-2023.  This label was required for each service overcurrent protective device.

This label was included as one of the options for labeling as part of the exception for the 2020 version of the NEC Section 110.16(B).  This label follows the rules of NFPA 70E.  This label does NOT include the date but would have met the requirements of NFPA 70-2020 but will not meet the requirements now found in NFPA 70-202 because the date is not present. 

Code making panel 1 noted that “Feeder supplied equipment” was added to the title and requirements of 110.16(B) as the panel concluded that the requirements in 110.16(B) must apply to both service equipment and feeder supplied equipment in other than dwelling units.  Incident energy is not solely dependent upon whether the equipment is service equipment. Labeling of incident energy is required by NFPA 70E on much more than that which is required in the NEC.  There were no references to the number of arc flash events at this equipment and nor should it be inferred that equipment 1000A and above has a higher likelihood or severity of incident energy.

[1] NFPA Report on Proposals for 2002 NEC, Page 74, LOG #2563, Ray A. Jones Electrical SAfety Consulting Services Inc. (ESCS Inc.)

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