Panel/Switchboard voltage matching

[Redskinsdb21]

So, we are designing a 480/277 switchboard. I want to feed a 480/277 lighting panel with one breaker from the switchboard for lighting in the building. This is ok right?

Then, I want to power the lighting circuits @ 277 V from lighting panel. Is 277 the line-to-neutral voltage in this case?

If so, to feed a lighting circuit in one room, I would just need a 1-pole breaker inside a 42-circuit panel? If I wanted to use 480 to feed something else from the panel I would need a 2-pole breaker and use 2 circuits in the 42-circuit panel?

Also, the cable from the switchboard to panel would need to be 4-wire, 3 for the 3 phases and 1 for neutral? Or would a 5 wire be required to include a ground?

 

[wcaseyharman]

That all sounds correct. If you need the neutral you’d need 5 conductors for a 3 phase branch/feeder circuit as you need the ground, unless you utilize metallic conduit for a ground conductor.

 

[waross]

Avoid shared neutrals on the lighting circuits.
A feedback on an open neutral will be lethal and you may find yourself testifying at an inquest.
I saw an industrial plane where someone saved money on cables by sharing neutrals.
It was condemned.
Rather than abandon and replace all of the cabling, three pole disconnects were installed on each three circuits that were sharing a neutral for LOTO.
That meant that to work on one circuit, three circuits must be shut down.
With 277 Volt lighting that was usually an entire floor and work must then be done in the dark.

 

[Redskinsdb21]

That all sounds correct. If you need the neutral you’d need 5 conductors for a 3 phase branch/feeder circuit as you need the ground, unless you utilize metallic conduit for a ground conductor.

I would need 5 wires from switchboard to panel as well correct?