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 Post subject: 130.3 Exception No. 1
PostPosted: Wed Apr 14, 2010 11:14 am 
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If a system meets all conditions listed in Exception No. 1, an arc flash hazard analysis is not required.

Say the system is at 120 volts and meets all conditions in Exception No. 1, does the arc flash boundary move to the 4ft default boundary? Or is there no arc flash boundary?


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PostPosted: Tue Apr 20, 2010 12:42 pm 
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A strict interpretation of the standard seems to require the 4 foot boundary for this case.

However, 130.3(B)(2) implies that you can use the task table to select PPE inside the 4 foot boundary. If the table recommends HRC0 for the task you want to do inside the 4 foot boundary then the impact seems negligible.


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PostPosted: Tue Jun 22, 2010 6:05 am 
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Can you use the exceptions?

If you meet all of the criteria for Exception No. 1, but determine that your incident energy is over 100kA cycles, are you now required to perform the calculations? 130.3 (A)(1)?


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PostPosted: Tue Jun 22, 2010 6:23 am 
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Yes, you would then be required to calculate the FP boundary.


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PostPosted: Tue Jun 22, 2010 7:15 am 
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If you are required to calculate the FPB if over 100kA cycles, whats the point of the exception? Either way you are going to have run calculations to determine whether or not you meet the 100kAC. Thus negating the exception to not have to.


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PostPosted: Tue Jun 22, 2010 8:29 am 
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seriouswatts wrote:
If you are required to calculate the FPB if over 100kA cycles, whats the point of the exception? Either way you are going to have run calculations to determine whether or not you meet the 100kAC. Thus negating the exception to not have to.


I did not say that the exception made any logical sense, just that the exception exists.


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PostPosted: Tue Jun 22, 2010 12:44 pm 
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seriouswatts wrote:
If you are required to calculate the FPB if over 100kA cycles, whats the point of the exception? Either way you are going to have run calculations to determine whether or not you meet the 100kAC. Thus negating the exception to not have to.


Technically, determing the 'kA cycles' is a short circuit and coordination analysis not an 'arc flash analysis'. :D :rolleyes:


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PostPosted: Thu Jun 24, 2010 3:54 am 
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A SSC/PDC study would give you your interrupting current to size your equipment (kAIC). The kA cycles is more for arc flash becasue you are concerned with the opening time of the device relative to the amount of fault current available.
My point is really, that you can meet all of the criteria for exception one to not have to do an arc flash analysis, but if you have low fault current your OCPD opening time could be long, and thus over the 100kA cycles. So either way you have run calculations, you can't just blindly take the exception.

Does that sound right?


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