I am dealing with a system with three voltage levels and don't know what do do with color-coding. We are using: black-red-blue as is typical for 208Y/120V brown-orange-yellow as is typical for 480Y/277V We also have 415Y/240V, 3-phase, 4-wire, and desire to identify it uniquely. Is there another color combination that is commonly used so it would unique?

I have also encountered a 240 volts corner grounded system in Akron, Ohio where the color coding was black, red, blue and the blue phase was the grounded phase because the neutral bar in the main fusible switch was on the right. I told a member of IBEW to think of it as a British corner grounded system. For a long time in England blue was neutral on commercial and industrial systems and black was neutral in residential systems. They changed that a few years ago so that all new residential wiring uses blue as the neutral. Iraq seems to like to use black for the neutral - the British version of romex looks a lot like our rubber cords and in previous tradition used black for neutral.

On of the U.S. manufacturers of MC cable offers cable with the brown, purple, yellow, slate color code - this avoids conflict with the color code for 4-wire delta systems. 120/240 4-wire delta is a good voltage for running \"toys\" in an otherwise 480 volt factory.

Oh, electromechanical demand meters used the A phase to power demand metering clocks and other accessories. In a form 15S meter for 4-wire delta systems the left stator metered the 2 low legs and the right stator metered the high leg. The newer 16S/17S and 8S/9S fits multiple voltages and phases meters still use this convention and will alarm service error if the high leg is not on the C phase. This is to maintain backwards compatibility in case an electromechanical meter needs to be temporarily installed if say an a kid\'s baseball knocks an electronic meter out of the socket.

Curiously, though, one make of electronic meters uses the C phase to power the electronics rather than the A phase that everybody else uses.

Mike Cole, mc5w at earthlink dot net

Time and time again we see voltages improperly stated. Please amend your documents to coincide with the NEC and IEEE stds.

208Y/120V is 3 ph, 4 wire, 480Y/277V is 3 ph 4 wire,

120/208Y is a 1 ph, 3 wire, open wye system.

240/120V is a 3 ph, 4 wire high leg delta.

If interested for other circuits: 3 phase 480V(corner-grounded Delta): Brown, Gray, Yellow 480V(Ungrounded Delta): Brown, Orange, Yellow 240V(corner-grounded Delta): Black, White, Blue 240V(Ungrounded Delta): Black, Red, Blue

Single phase 120V (grounded): Black, white(Neutral)

Direct current (DC) - Positive (+) : RED, Negative (-) : Black

Is there a rule for correlation of phase (A,B,C) to color for phase sequence?

Very simply from all my installation experiance 250V and below are Bk, RD BL and WHT. and for all 250V and above it's BRWN, ORG, YEL & Gray. A delta system with a "wild leg" is always installed on the "B" Phase and marked red or Orange. it's a very simple way to keep a standard when installing.

There was at one time in the NEC, for 240/120V Delta system with a high leg (208V), a requirement that orange be used on the "high leg" or B phase. Is that still a requirement? I can't find it in the 2005 NEC.

very good subject