What exactly is required when mixing voltages, ie. 208 & 277 in the same J-Boxes and conduits.
As far as labeling, color codes etc.
I know what is preferable, but what is required by code.
Thanks in Advance.

They need to be separated by a non-conductive barrier.

No barrier is required unless two devices in the same box have more than 300 volts between them.

.....And at least one of those devices is a snap switch

Don't all of the conductors have to have an insulation rating appropriate for the highest voltage used?
Joe

Yes, they do.
All of the Building Wire that I'm accustomed to working with has insulation rated at 600V, so it would qualify for highground's original query.

Now my question:
What is the insulation rating of Cat5/Cat6 etc. cable?
How about Bell Wire/Thermostat Wire?

Most CAT5/6 I've seen is rated at 300 volts. I'll check back on the new CAT6 I just used on a job, it's in the warehouse...

I've seen t-stat wire at both 150v and 300 volts. Not sure about bell wire.

Anyone? Anyone? Bueller? Bueller?

See 210.5 in the 2005 NEC.
Don

the code section should be 210.5(C)

[This message has been edited by resqcapt19 (edited 01-19-2006).]

Then you have to look at 725.55(A). Even if the communications and controls cables have a voltage rating higher than that of the power conductors, you still can't mix them in the same raceway.
Don

725.55(D) allows for mixing voltage class wires so long as the class 2 wires pertain to a device in that box. A nice one for lighting control systems.

Not sure of the wording of 2005, but 200.6d of previous codes has covered this situation. Not only applies to different voltages, but specificaly different systems, reguardless of voltage. (Say 3 different tranformers of the same voltage feeding panels with the branch circuits in a gutter, box, or in conduit together.)

300.3(C)(1)
Conductors of circuits rated 600v, nominal, or less, ac circuits, or dc circuits, shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.
As outlined in 725.55(A), this is not permitted with circuits considered class 2 or class 3 circuits.
BUT...I've been on several projects where the project specs did not allow the mixing of different voltages, or different systems, in the same raceways.

[This message has been edited by XtheEdgeX (edited 01-22-2006).]

Just read the 2005 code mentioned by Don, and it seems it is very simularly worded to the 200.6 code section that is specific to grounded conductors, but adds system identification for phase conductors as well. (I guess just short of going as far to have color codes involved in the NEC.)
https://www.electrical-contractor.net/ubb/Forum19/HTML/000061.html