How the NEC and NFPA 70E team up to minimize risk on energized equipment
NFPA Journal, September/October 2010
The new labeling requirement in the 2009 edition of NFPA 70E® is intended to work with the labeling requirement in NFPA 70®, National Electrical Code® (NEC®), and to provide the necessary information on the required level of personal protective equipment (PPE).
For example, a newly installed 480-volt motor control center (MCC) bears the label required by Section 110.16 of the NEC that provides a general arc flash hazard warning. The MCC is energized so that start-up, troubleshooting, and commissioning of supplied equipment and processes can get under way, which means it is now subject to NFPA 70E requirements covering safe work practices, including the PPE labeling requirement of Section 130.3(C) of NFPA 70E.
Diagnostic and troubleshooting tasks on energized equipment are permitted by Section 130.1(A)(2) of NFPA 70E, meaning that anyone working on exposed energized conductors and circuit parts within the MCC, including those working for contractors and those employed by the building or plant owner or operator, is exposed to shock and arc flash hazards. That’s why the electrical safety–related work practices covered in Article 110 of NFPA 70E must be implemented.
One of the primary considerations is the selection of the appropriate level of PPE based on the type of task to be performed and the potential exposure to shock and arc flash hazards. A shock and arc flash hazard analysis must be performed, and, if an arc flash hazard exists, the equipment is required to be field–marked according to Section 130.3(C) of NFPA 70E.
In short: The NEC Section 110.16 marking provides a general warning as part of an overall effort to increase employee awareness of a possible arc flash hazard. The NFPA 70E Section 130.3(C) marking is more detailed because a decision has been made to work on energized electrical equipment. The NFPA 70E marking is provided at the “point of use,” or, in this case, the “point of arc flash hazard,” and conveys the vital information on PPE selection to those who will be directly exposed to the hazards associated with working on energized electrical conductors and circuit parts.
An important point to keep in mind is that the information on the NFPA 70E label is only required to convey the available incident energy in calories per square centimeter calculated through the incident energy analysis specified in Section 130.3(B) or to specify the “minimum arc rating of PPE,” also expressed in calories per square centimeter, that is associated with using Tables 130.7(C)(9), (C)(10), and (C)(11). Because most users of Tables 130.7(C)(9) through (C)(11) are more familiar with the hazard/risk categories—that is, 0 through 4—equipment labels where use of the tables is appropriate often contain the hazard/risk category numerical designator.
Where an incident energy level is calculated, it is not intended that the calculated number be converted into a hazard/risk category using the minimum arc ratings for PPE from Table 130.7(C)(11). This is like mixing apples and oranges. NFPA 70E provides two separate methods by which to select PPE, and they should be used independently. One way is to determine a caloric value by calculating incident energy, and the other is to use the hazard/risk categories in the tables permitted by Section 130.3, Exception No. 2—thus the requirement for the label to specify either the available incident energy or the required level of PPE.
The label can contain other information, but the standard only requires the information directly related to selecting the PPE for the task to be performed. Neither the NEC nor NFPA 70E preclude using a single label to meet the requirements of NEC Section 110.16 and NFPA 70E Section 130.3(C) as long as the label provides the general warning as well as the information on PPE selection.
Jeffrey Sargent is NFPA's senior electrical specilist and is staff liason for NFPA 70E.