What am I missing?

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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
I was doing a job this week on a building that had a 800 amp 480 volt service, the building owner had an Arc flash study done, and had the gear and panels labeled with the PPE requirements. The 800 amp 480 volt panel required 3.9 cal PPE, while the 200 amp 120/208 volt panel called for 9.8 cal. what is wrong with this picture? One would assume the fault current available at the 800 amp panel would be much greater than the 200 amp panel. Surely the breaker or fuse feeding that panel could not interupt the current that much faster in order to get a lower cal rating? I myself would not wear 3.9 cal in front of a 480 volt panel, regardless of what a engineer says! All of the major arc flash incidents I have ever seen were not at the lower voltages, but at the 480 volt level.
 
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