Is it reasonable to use the Calculated Incident Energy method for all 480Y/277V equipment in a facility but to revert to the table method for 208Y/120V panelboards being fed by 112kVA transformers or smaller. i.e. the first category in the Table applicable to 240V or less, 25kAIC or less with clearing time of 2 cycles

I mean, is it not true that all 400A and less, 10kAIC breakers (which is all you need down stream of this range of dry types) trip in 1.5 cycles AND that the available down stream of a standard 112kVA or smaller will always be less than 10kAIC.

The table gives you a PPE of 1 for this set of circumstances. Is it not always a safe bet that such a panel, were you to calculated the incident energy would never result in a requirement for PPE higher than level 1?

It appears that you are referring to what was commonly referred to as the 112.5kVA and less exemption in IEEE 1584-2002. This exemption is no longer valid as it was superseded in IEEE 1584-2018. IEEE 1584-2018 states that arcs are less sustainable for 2000A or less and 240V and less. So you need to calculate the fault current to determine the likelyhood of an arc so you might as well determine the incident energy at that point.

Hello, if you are already conducting the incident energy analysis for the 480 Volt system, my advice would be to carry on down your 208 systems. The IEEE 1584 standard has been revised to the 2018 edition and the less than 240 Volt and 125 KVA no longer applies. I hope that this is of some help

Some of the software programs, such as SKM PowerTools for Windows, has an option to use the "IEEE 1584-2018 arcs are less sustainable for 2000A or less and 240V and less." exception. Using this exception will reduce some of the data collection time and effort for these lower energy locations.

Just wondering why we tend to ignore the NESC tables which are based upon substantial test data. Unless something has changed there is little or no 1584 substantiated data on the 208/240 systems. If you look at the data that exists, in many cases the tests are populated with specific tests where the arc would not sustain itself. Again i could be wrong, but, it seems that 1584 has largely ignored these systems.