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 Post subject: Two pole breakers at 480V
PostPosted: Wed Oct 27, 2010 11:02 am 

Joined: Tue Jun 15, 2010 1:41 pm
Posts: 2
What is the best approach to calculate incident energy for the two pole breakers at 480V? I came across lighting loads fed from two pole breakers with operating voltage of 480V. Software program that I am using excludes cables having only 2 phases and 2 phase loads from arc flash study.

Would it be accurate to say that all two pole breakers at 480V have Category zero or just exclude them from the study?


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PostPosted: Wed Oct 27, 2010 11:45 am 
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Joined: Tue Oct 26, 2010 5:00 pm
Posts: 188
Location: Maple Valley, WA.
There are equations in IEEE 1584 or NFPA 70E that allow you to calculate the AF energy for line to ground or single phase circuits. When we model these circuits, we will treat them as three phase circuits or breakers. Until there are equations that will allow you to determine the energy levels for these devices, we believe that this is the best method instead of assuming they are category 0.

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Robert Fuhr, P.E.; P.Eng.
PowerStudies


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PostPosted: Thu Apr 28, 2011 1:13 pm 

Joined: Tue Apr 12, 2011 6:11 am
Posts: 17
Location: Oregon, USA
Robert, I take the first line in your preceding comment . . .

"There are equations in IEEE 1584 or NFPA 70E that . . . "

. . . was intended to read . . .

"There are NO equations in IEEE 1584 or NFPA 70E that . . . "

I would agree that under these circumstances, your recommendation certainly seems the most reasonable approach.


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