Hazard Risk Table vs. Calcs.

If NFPA 70E Hazard Risk Tables indicate I need Category 2 protection but my detailed calculations show I only need Cagegory 1, do I still have to use Category 2?

Hazard Risk Tables

My understanding it the tables are in lieu of calculations. If you perform the calcs then those results are used.

If your do the calcs you follow them. The charts are there if you can not perform them and need a starting point. The charts may make you wear more PPE then the calcs come up with. Just be careful and double check your calcs.

Table footnotes

If you check the notes at the end of the 130.7 Table, they spell out what circuit criteria the table values are applicable for. If you performed the calculations properly, you are most likely safe. Read those notes at the end of the table and you'll probably notice that the parameters of the circuits your calculated are vastly different.

Hazard Risk Table vs. Calcs.

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If NFPA 70E Hazard Risk Tables indicate I need Category 2 protection but my detailed calculations show I only need Cagegory 1, do I still have to use Category 2?
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To your question above: It's important to keep in mind these tables are the MINIMUM requirements and guidelines. I would suggest going up to Cat 2 protection. I'd rather be a little over than a little under or just meeting the minimum requirements.

RJ
www.jacmangroupsafety.com

I don't know that we need to be attempting to rewrite the standard. It was created as a safety guideline and I believe that we are fine to take the advice at this point. You have the option to live with the tables or do your calcs. If you do the calcs and are comfortable with them, then that is all I would use....no more or less. If we are to create our own safety margins, then how about a factor of 3 or 4? After all, we do not know the level of margin, if any, that might already be included in the tables.

Maybe someone else does know?

Alan

I have an FR shirt that is rated 8.3 calories. I am begining to wonder if the manufacturers are adding a little cushion into this as well. i.e. cat 2 is 8 calories and the shirt is slightly above that number.