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 Post subject: Re: Tables Vs. Incident Energy Method
PostPosted: Mon Aug 03, 2015 1:00 pm 
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Please read the attached file. I wrote this after a heated argument with someone at the Electrical Safety Workshop in Louisville this past January. In my attachments I give example there the use of tables would get your in big trouble. Since this is such a serious topic I need to pass on the cost of one accident I'm investigating. The medical cost have now reached $6,000,000 for one person..


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 Post subject: Re: Tables Vs. Incident Energy Method
PostPosted: Tue Aug 04, 2015 7:18 am 
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Location: Toronto
jcp@pfeiffereng.com wrote:
Please read the attached file. I wrote this after a heated argument with someone at the Electrical Safety Workshop in Louisville this past January. In my attachments I give example there the use of tables would get your in big trouble. Since this is such a serious topic I need to pass on the cost of one accident I'm investigating. The medical cost have now reached $6,000,000 for one person..


I agree with your observations. Actually, the odds of specifying adequate arc flash PPE using the NFPA 70E tables (50%) are about equal to the odds of survival of placing a single round in a revolver, spinning the cylinder, placing the muzzle against ones head, pulling the trigger and repeating the procedure four (4) times in a row. I wonder who will ultimately pay the bill.


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 Post subject: Re: Tables Vs. Incident Energy Method
PostPosted: Wed Aug 05, 2015 9:45 am 
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I for one would like to see an improved table, something on the order of what's in NESC. In fact the NESC tables USED to be in 70E prior to 2015 edition. I even put in a proposal to keep them in there which was rejected.

The good thing about the NESC tables is that EPRI and a couple utilities have done extensive testing over a huge range of fault currents to arrive at an equipment specific table that represents actual real world conditions whereas IEEE 1584 is based on synthetic tests performed on a standardized testing environment, which is for the most part intended to mimic "typical" equipment found in an industrial setting. It would not be very close to say a dead front padmount transformer or a network box, and that's where NESC has paved the way.

We would be better off if the equipment table actually reflected real testing for incident energy based on testing on actual equipment as the NESC tests do. Their table covers everything adequately except one type of equipment. Switchgear and MCC's aren't really covered well by NESC which more or less references the end user to IEEE 1584. However for a huge variety of commercial equipment such as dead front padmount transformers, disconnects, lighting panels and 480 V panelboards, it is a much better reference compared to 70E which is relying 100% on IEEE 1584 results.


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