I'm trying to figure out how to model a portion of this system. A contractor has recently installed four new motor feeders, and they all pass through a single disconnect enclosure. Each feeder has a 400A breaker at the MCC, and they each also have a 400A breaker in this new enclosure. I imagine the incident energy to be higher than the worst case for any single feeder, but don't think I should add them all together either. Has anybody dealt with something similar?

It looks more or less like this:

What software are you using? An arc on any one of the breakers would expand to include all the others. One way is to model the enclosure as a bus on the load side of all the breakers and then fault that bus. I use EasyPower so the bus would be set to ignore the main breakers, on Integrated method and that would give you the incident energy for that box.

I am also using EasyPower.

That is how we approach most enclosures, but this equipment has several motors and control panels below it. I don't want to erroneously affect the IE at those panels. Maybe I'll run that as a scenario and see if anything changes significantly.

Thanks for the help.

Yes you will have to do a separate analysis for the common enclosure and then do another for the equipment downstream with each feed as it is from the common enclosure.

Does EasyPower have an easy way to do that, or would that have to be done manually?

You would have to model it twice but that is not hard. One model would be with the single enclosure with all 4 breakers connected to a bus. The other with the system as it normally is. The single connected bus model would give you the incident energy for that enclosure.

Are all 4 breakers in the enclosure fed from the same bus or multiple different buses?

They are all fed from individual 400A breakers on the same MCC bus.