NFPA 79 (section from
Sec. 16.1.3 allows you to use other colors for the purpose of identification as follows:
• Black represents ungrounded line, load and control conductors at line voltage.
• Red represents ungrounded AC control conductors, at less than line voltage.
• Blue represents ungrounded DC control conductors.
•
Yellow represents ungrounded control circuit conductors that may remain energized when the main disconnecting means is in the OFF position. These conductors must be yellow throughout the entire circuit, including wiring in the control panel and the external field wiring. International and European Standards require you to use
orange for this purpose (see IEC 204-1 for specific requirements).
• White or natural gray represents a grounded circuit conductor.
• White with blue stripe represents a grounded DC current-carrying circuit conductor. International and European standards require you to use light blue for the neutral conductor (see IEC 204-1 for specific requirements).
•
White with yellow stripe represents grounded AC current-carrying control circuit conductors that remain energized when the disconnecting means is in the OFF position. For additional circuits powered from different sources that remain energized when the main disconnecting means is in the OFF position, you must use striping colors other than green, yellow or blue to uniquely identify the grounded conductors.
The above states "Allows you to use other colors..."....it doesn't state you must use these colors. I think the color of wire insulation would depend on the source, not the destination. How can it be identified as orange or yellow from the source (since it wouldn't be foreign voltage at the source)?
In my projects in Chemical Plants and refineries, we aren't building the NFPA specified panels, so never paid attention to this. The only thing I've done, is to label the cabinet with "Caution: Foreign Voltage Present", or something to that effect.
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