Considering an Arc Flash Analysis? Read on, and next week look for Part III in this series: "What to do Between Now and Completing an Arc Flash Analysis"

1. Perhaps the greatest gap in the NFPA 70E 130.7 Chart is what it doesn’t say. The chart does not discuss the greatest risk factor of all, an arc flash that is too severe for any PPE to protect people involved in the flash. Taking into consideration the information from arc flash studies, most companies will have 2% - 4% of their equipment that exceed the capability of PPE to protect their employees (i.e. greater than Category 4). The chart does not address this nor has any way to identify it. The only way to determine where these situations exist without performing the complete analysis.

2. The chart is conservative is many areas and will advise to use PPE that are 1 or even 2 categories above what may actually be required. In theory, it may seem like more is better, but in practical applications it is not.

      a. Investing in PPE for higher categories that you do not need can be more expensive than the cost savings of not doing an analysis for some companies.

      b. The higher up the chart one goes with the PPE, the more protective and also the more difficult and perhaps even dangerous to work in. A full Cat 4 PPE suit is not easy or comfortable to work in. Workers complain of the suits being hot, obstructing vision and losing dexterity. Loss of dexterity is a major concern for some workers because they are more likely to drop things such as tools or bolts, which could lead to an arc flash. Due to this, some workers have stated that they believe there is a higher chance of an arc flash happening when wearing Cat 4 PPE.

       c. If the PPE seems overly excessive, knowledgeable workers may question it and start making decisions based on their knowledge and experience and pay less attention to the chart.

3. To be compliant, warning labels must be applied to the equipment in order to warn workers of the hazard. Because the 130.7 chart is based in part off of tasks, the risk / hazard category can range from a “0” to a “4”, so it’s not possible to provide just one risk hazard category that identifies the proper PPE. There are the following options on the labels;

       a. Provide an arc flash warning label with information including the voltage and other information per NEC standards. This would require the workers to then reference and read the 130.7 chart, which leaves room for worker interpretation and errors.

       b. Provide a label that details the different tasks and hazard / risk categories for each piece of equipment along with the PPE required. The problem with this is that there is so much information that you might need 8” x 18” of uninterrupted label space to provide all the information, which isn’t very practical. Further, it still leaves the worker to read and interpret the information, leading to potential errors.

       c. Provide arc flash warning labels using only the highest category of risk hazard for any tasks for that piece of equipment. This would end up being a Cat 4 for most situations, meaning workers would be required to dress in a full Cat 4 PPE. As mentioned above, wearing a lot more PPE can cost a lot more, can be considered more likely to cause accidents and can lead workers to not believing the information on the labels and therefore, start making their own decisions.

4. Even with knowing the information on your electrical system to apply to the chart, the chart may still advise you to do an arc flash analysis for particular tasks or any for assumptions that do not fall within the parameters of the chart.

Costs & Time Involved in Gathering Information to Use the Chart.

If a company does not already have all the information to use the chart, they must go through an engineering analysis process that includes data collection, short circuit study and determination of fault clearing times. Then labels must be printed and applied to equipment to warn the workers. This process covers a big part of the cost of actually doing a proper arc flash, so it’s not a tremendous cost savings versus actually doing the analysis.

Further, for those situations that do not fit neatly into the 130.7 chart, an arc flash analysis is required anyways, making it the same cost as just staring out to do a full analysis.

Summary of Using the NFPA 70E Charts

Very few companies can actually use or do actually use the NFPA 70E 130.7 charts to be compliant for the following reasons:

• Without knowledge of short circuit current or fault clearing times, the charts can not be used.

• Gathering the information to use the charts can be nearly as expensive as just doing an arc flash analysis ( and can be even more if unnecessary PPE is purchased ).

• Even with the proper information, if the results don’t match the criteria or a task does not match the criteria, an arc flash analysis is required and the chart can not be used.

• The chart is conservative and may recommend PPE that really isn’t necessary leading to additional costs and potentially increasing the chance of an accident happening.

• The chart may still be inadequate by not identifying the most dangerous risk; greater than Cat 4.

• There are no good labeling options to warn workers.

When taking into consideration the time and cost to properly use the NFPA 70E 130.7 chart and knowing the shortcomings of the chart after implemented, it doesn’t make a whole lot of sense from either an investment standpoint or safety standpoint to choose to use the NFPA 70E 130.7 chart versus just doing an arc flash analysis.