NFPA Table 130.7 (C) (9) identifies arc flash hazard risk categories based on tasks being performed and the equipment which its being performed on. On the surface, this table appears to be an easy and low-cost solution, however, it has many conditions and potential problems.
Using the NFPA Table 130.7 is acceptable if you know your short circuit current and fault clearing time AND these results fall within the parameters of using the table. If you do not know your short circuit current and fault clearing time of each piece of the equipment or the short circuit current or clearing times exceed the parameters of using the table, then the table can not be used and an arc flash study / analysis must be conducted.
The problem here is that very few facilities have up-to-date electrical one-line drawings, let alone any knowledge as to what their short circuit current or fault clearing times are. In order to determine the short circuit current and the fault clearing times, an electrical engineering analysis must be completed, which is comprised primarily of the same work process and costs in doing an arc flash analysis, so unless this information is already known and accurate, an engineering analysis will need to be done anyways. Even once the engineering study is completed, most facilities and plants will find that they have equipment that falls outside of the table, which will require them to do a full arc flash analysis anyways.
Independent of having the right information to use the charts, the recommendations of the table have some gaps and are, in general, widely contested. In particular, the table has the following deficiencies:
1.The NFPA 70E Table does not address or have any ratings for the highest arc flash hazard category; Greater than Category
2. The NFPA 70E Table does not address all tasks. If the task one is performing is not listed on the table, the table can not be used.
3. Actual engineering studies have found that the NFPA 70E table can suggest using far more protective equipment than is actually necessary. Working in Cat 3 or Cat 4 PPE can be hot, difficult and result in loss of dexterity and vision. If the work does not require this for safety purposes, the worker should not be exposed to this. Further, those experienced in working on electrical equipment may realize that the table recommendations are over-protective and therefore, the table gets devalued or ignored because of lack of accuracy.
4. Labeling: Labels are still required to warn workers of the hazards and must included specific information. Using the table alone does not satisfy the label requirements. Further, providing just the information from the charts requires a worker to read and self-determine the hazard category, adding room for error.
5. No ability to mitigate hazards. Without doing an arc flash study, there is no ability to identify and mitigate the hazards down to a lower level.