3-wire branch circuit

[Larry Fishel]

I know I've seen this addressed somewhere, but I'm having trouble finding it. I'm planning to run a "3-wire branch circuit" as described by the NEC, out to a shed, one groundED wire and two hots from opposite legs of the service (and of course a groundING wire), individual wires through conduit, not cable. Should the two hot wires be different colors to distingush the two "phases", make sure noone in the future hooks them together and to indicate the 240 volt potential? I see where that is specifically required for a 240 volt circuit (running 240 volt equipment) and it's commonly done with 3 wire CABLE, but no mention of what to do with a 3-wire circuit through conduit. Red, black, white (and green) sounds like the reasonable thing to do, but I want to make sure it doesn't violate some obscure rule I'm missing...

[gfretwell]

You can legally do it with any color for the ungrounded (hot) conductors except whirte grey or green. If you are pulling wire in pipe it is a good idea to identify each phase differently. Your 120/240v circuit can feed both 120 and 240v loads if you use a 2 pole breaker.

[shoppa]

I'm not a professional electrician, but I can tell you that most subpanels I've seen are fed with two black wires for the two hots, and that black and red is also a combination I've seen.

That said, your local inspector might not really care what the NEC allows, he might insist that you have some arbitrary color scheme (and he may even be able to pull the local codes out of his ass,err, um, back pocket.)

Tim.

[SQLit]

There is no color code in the NEC for ungrounded conductors (hots). I have tried a couple of times but they refuse to hear my petition.

Motorola used black-red-blue for 277/480v and brown, yellow and orange for

120/208v. Which is backward from what most of us use.

I worked for a utility once that used red, white and blue for their phase marking. Now that was confusing.

Do what you want make sure that the wire is big enough for the load at that distance.

[Tom Horne, Electrician]

I know that this may sound like a petty quibble but since this forum is world wide is is worth saying that under the US National Electric Code there is one color code for ungrounded conductors. Most of us do not have to deal with it but it is still present in some services. Three phase delta 240 volt wiring with one phase center tapped to provide 120 volts must have the conductor with the higher voltage to ground coded orange. Also some local codes do have a color code in them. The District of Columbia being one example.

[Chris Lewis]

[Other examples of confused color schemes for 3 phase circuits]

To Larry: red, black, white and green (individual conductors in conduit), or bare (sheathed cable) is the right thing to do - and matches usual usage with /3 cable.

Black, black, white and green (or bare) is probably acceptable, but not the best thing to do. But, anybody who parallels hots gets what they deserve - it's ALWAYS wrong to parallel hots in anything you're likely to see in residential circuits.

To SQLit: of _course_ there's a NEC color code for ungrounded conductors. There may be a lot of confusion with large 3 phase feeds (especially given that the NEC doesn't get upset about strange color coding when the wire is big enough - ie: service entrance grounding conductors are permitted to be black IIRC), but that's not what we're talking about.

To Tom: It's perhaps a mistake to say "most of us do not have to deal with it" w.r.t. color codes - or at least be clearer. Anybody dealing with residential wiring _does_ have to deal with color codes. At least they're simpler than the industrial wiring side.

[Larry Fishel]

Thanks everyone. As far as local codes, I guess I should have mentioned that I am in unincorporated Dade County, FL. Though they are at least one version behind (I think two as of this year), Dade County has adopted the NEC codes with one or two minor exceptions.

[gfretwell]

Dade county is on the Florida building code which adopted the 2002 NEC unaltered. There are NO local codes in Florida. Now if we could just explain that to the inspectors. 2005 code is scheduled to be adopted July 06

[Thomas D. Horne, FF EMT]

with /3 cable.

To be clear I meant that most of us do not have to deal with High leg three phase delta services.