IEEE 1584 and the 125KVA exemption.. gone?

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cornbread

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Going back and re-validating some old arc flash labels using Etap. Back in the day when we had the 125KVA exemption for 208/120V we had Cat 0, I know Cat 0 is gone with the new NFPA 70E, but I was surprised to find we had a couple of panels that calculated to a Cat 3 with a 45KVA transformer. I find it troubling that we had such a dramatic change with the new rules. We are looking at changing some fusing to lower the arc flash, but questions our design criteria. It is what it is, but I hate asking for money each time the code gets updated.
I’m curious if anyone else had similar issues and how they are addressing issues?
 
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wbdvt

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Location
Rutland, VT, USA
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Electrical Engineer, PE
The exemption for a <125kVA transformer and below 240V still exists in IEEE 1584-2002, so it is still a valid exemption. The reason is because of results like you see in your example. In testing for IEEE 1584, an arc was only able to be sustained at 208V in one test. There is rumor that in the new IEEE 1584, this exemption will be replaced with a fault current level.
 
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cornbread

Senior Member
With the exemption gone, we have Cat 3 potential. Pretty sure the old panels can't handle a Cat 3 event? I'm speculating, but I would think the door & breakers would go flying if a fault were to occur??
 
ron

ron

Senior Member
Location
New York, 40.7514,-73.9925
cornbread said:
With the exemption gone, we have Cat 3 potential. Pretty sure the old panels can't handle a Cat 3 event? I'm speculating, but I would think the door & breakers would go flying if a fault were to occur??
Click to expand...
Unless the equipment is arc resistant, equipment is not test for the capability to withstand arc levels that are derived from the 1584 or 70E calcs
 
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