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...
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
Your 120/240v circuit can feed both 120 and 240v loads if you use a 2
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,
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.
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
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
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.
"This alternating current stuff is just a fad. It is much too dangerous
[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
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
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.
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.