[RE-wrenches] useful info on wire color coding

R Ray Walters ray at solarray.com
Sat Aug 21 21:22:48 PDT 2010


Interesting, there isn't a code requirement to color code for phase rotation, but it is common practice for black, red, blue to correspond to clockwise rotation. Also notice on the DC table, that John Wiles recommends (but isn't NEC required) color coding for a positive grounded system: 
white for positive, 	black for negative.
I think the phase rotation and DC polarity issues are analogous: get the colors backwards, and the motor turns backwards, AC or DC. (and if we're lucky,  that's all that goes wrong)
If we're unlucky, at least on DC, the inverter belches smoke and fire.

R. Walters
ray at solarray.com
Solar Engineer




On Aug 21, 2010, at 4:44 PM, Marco Mangelsdorf wrote:

> But I’m still trying to determine if the black-red-blue and brown-orange-yellow sequences are appropriate for clockwise or counter-clockwise phase rotations.
>  
> marco
> US, AC:The US National Electrical Code only mandates white (or grey) for the neutral power conductor and bare copper, green, or green with yellow stripe for the protective ground. In principle any other colors except these may be used for the power conductors. Black, red, and blue are used for 208 VAC three-phase; brown, orange and yellow are used for 480 VAC. Conductors larger than #6 AWG are only available in black and are color taped at the ends.
> US AC power circuit wiring color codes.
> Function
> label
> Color, common
> Color, alternative
> Protective ground
> PG
> bare, green, or green-yellow
> green
> Neutral
> N
> white
> grey
> Line, single phase
> L
> black or red (2nd hot)
>  
> Line, 3-phase
> L1
> black
> brown
> Line, 3-phase
> L2
> red
> orange
> Line, 3-phase
> L3
> blue
> yellow
>  
> <image001.png>
> US DC power: The US National Electrical Code (for both AC and DC) mandates that the grounded neutral conductor of a power system be white or grey. The protective ground must be bare, green or green-yellow striped. Hot (active) wires may be any other colors except these. However, common practice (per local electrical inspectors) is for the first hot (live or active) wire to be black and the second hot to be red. The recommendations in Table below are by Wiles. [JWi] He makes no recommendation for ungrounded power system colors. Usage of the ungrounded system is discouraged for safety. However, red (+) and black (-) follows the coloring of the grounded systems in the table.
> US recommended DC power circuit wiring color codes.
> Function
> label
> Color
> Protective ground
> PG
> bare, green, or green-yellow
>  2-wire ungrounded DC Power System
>  
>  
> Positive
> L+
> no recommendation (red)
> Negative
> L-
> no recommendation (black)
>  2-wire grounded DC Power System
>  
>  
> Positive (of a negative grounded) circuit
> L+
> red
> Negative (of a negative grounded) circuit
> N
> white
> Positive (of a positive grounded) circuit
> N
> white
> Negative (of a positive grounded) circuit
> L-
> black
>  3-wire grounded DC Power System
>  
>  
> Positive
> L+
> red
> Mid-wire (center tap)
> N
> white
> Negative
> L-
> black
>  
>  
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