Maybe to reduce the likelihood of this scenario: electrical worker mistakes DC conductor for an AC conductor. Tests for voltage with an AC voltmeter, but it reads 0 because there is only DC (is this correct)? Gets shocked as a result.
If there is a fault there is a concern that the peanut butter will mix with the chocolate. We don't want DC on the AC conductors and vice versa in the event of a cross conductor fault since the protection system have different ratings.
I don't find that argument to make any sense. Couldn't the same thing be said of AC+AC conductors? Say small and large AC conductors in the same conduit or raceway or box? I could have some 12 gauge conductors in a circuit with some big feeder conductors and there's no restriction, and if there is a cross fault that big circuit could turn those 12 gauge conductors into chowder.
Even if the DC is non-PV? You certainly seem to work with more AHJs that ignore what the code explicitly permit than most do.
Yeah I don't really see the reason to allow 600V AC in the same conduit as 120V AC circuits, but not 600V DC. Either of the 600V sources is going to wreak a lot of havoc if it gets onto the 120V circuit.
The main one who said that was CPS in San Antonio; they have their rules and they do not explain every one of them.
