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Survey: NFPA 70E PPE Category Table Parameters
https://brainfiller.com/arcflashforum/viewtopic.php?f=2&t=5661		 Page 1 of 1
Author:  Jim Phillips (brainfiller) [ Sun Feb 05, 2023 9:22 am ]
Post subject:  Survey: NFPA 70E PPE Category Table Parameters
NFPA 70E Tables 130.7(C)(15)(a) and (b) list Arc Flash PPE categories based on equipment. Each equipment and associated PPE category also list the parameters of maximum fault current and maximum clearing time since the severity of an arc flash is dependent on both. However, these parameters can sometimes be difficult to determine.
Here is the question:

When using 70E arc flash PPE Tables, are you able to consider:
- Available fault current
- Fault clearing time
- I don’t use the tables
Select up to 2 answers
Author:  phil.haataja [ Mon Feb 06, 2023 10:17 am ]
Post subject:  Re: NFPA 70E PPE Category Table Parameters
It's interesting that so many people say they use the tables, but when quizzed, confess that they don't know how to calculate maximum available fault current.
Author:  Jeff S [ Mon Feb 06, 2023 1:17 pm ]
Post subject:  Re: Survey: NFPA 70E PPE Category Table Parameters
I never understood the tables. In order to use them, you must know the available fault current and protective device clearing time. I don't know anybody, literally, that can tell you the device clearing time for a specific device for a specific fault level without looking up the manufacturers TCC. If you're going to go to that much effort, you might as well have just done an IEEE 1584 calculation. I'd be willing to bet that the tables have NEVER been utilized properly.

I've used the tables before when gathering system data for doing an initial arc flash study at a site that never previously had one done so that I could estimate what PPE I needed to wear. But like I mentioned, I'm gathering system data, so there's no way for me to know what the available short-circuit is yet or even what the specific device that is supposed to clear, let alone how fast it would clear.
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