Jon,
"how it should' read" Why Thank You... [swagger]

"I think that the coding we are discussing here is good workmanship." What do you mean by that? [Linked Image]

Anyway, 210.4d says, "Where more than one nominal voltage system exists..." As opposed to a system not of "Nominal Voltage". It does not say they have to be two different nominal voltages, it says "more than one". Even though that would be its most common use. There are a few inspectors here who read it that way too. Then again they have a tendancy to read things differently here, its the water. Sorry, Jon, I'm sticking to my guns here.

And, yes it would only apply to multi-wire branch circuits. But you might as well make it easy on yourself, cause it says when they "exist in a building", it doesn't say in the same conduit, just that they "exist in a building".

Anyway, it would be funny, depending on how you look at it, if a hot and neutral got connected by accident. You could sync the generating sources from there. As they could be anywhere from 0-180 dregrees out of phase at anytime. Variations in freq from either, and you'd have that eery dimming effect. Actually, you might have some of that anyway, as the lights will stobe differently. I've seen it when doing large multiple generator installations in the military. Over a distance you get that road glare type effect. That building is going to be spooky. This is one job that needs an engineer, as it might need one in the future.

If it were me... I would take both sources to the same location, and have a simple transfer switch.

Mark Heller
"Well - I oughta....." -Jackie Gleason