AnsweredAssumed Answered

NFPA-79 Wire Color Code

Question asked by rcramereleceng on Jan 10, 2020
Latest reply on Jan 16, 2020 by rcramereleceng

The NFPA-79 Wire Color Code is important for any person to quickly identify Circuits.  Consequences of using the wrong Wire Color could be lethal.


The NEC calls out (3) Colors:

     *     Green (GRN):  Green is Ground (the world around) or Green with a Yellow Stripe (YEL Tracer)(GRN/YEL)

     *     White (WHT):  White is the Grounded Neutral (if the Neutral is not Grounded - it should not be White)

     *     Grey (GRY):  Grey is also the Grounded Neutral for specific applications (i.e. Lighting)


NFPA-79 13.2  Identification of Conductors

     *     Green (GRN): Ground, Earth, Bond, Chassis, Frame, PE (Protective Earth), Safety, other Wires colors used

            (as temporary substitute or Multi-Conductor Cables have (3) Green Electrical Tape Bands at the connection).

     *     White (WHT) or Grey (GRY):  Grounded Conductor (as opposed to "Grounding" Conductor) Neutral or Common.

     *     Black (BLK):  Primary AC (ungrounded) 480V Nominal (208V - 505V) (and >50V DC, i.e. Brake Resistors)

     *     Red (RED):  Secondary AC (ungrounded) 120V (Nominal; 100V-125V)

     *     Brown, Orange, Yellow (BRN,ORG,YEL): not specified but used in conjunction for 3-Phase applications

            requiring easy identification of Phases (14 - 6AWG), otherwise (BLK)

     *     Blue (BLU):  DC (ungrounded) Control Wires (24V DC), also;

            White with a Blue Stripe (WHT/BLU):  for 0V DC (Grounded)

            Blue with a White Stripe (BLU/WHT):  not specified but often used for 0V DC Grounded or Floating


By rights, any Color can be used, so long as it is called out on the Drawing. 

Exceptions include special applications, such as; 

     *     High Temp.:  Cloth (Any Color)

     *     Battery: (RED) = ( + ), (BLK) = ( - ) {look at your Multi-Meter and Car Battery}

     *     Thermocouple Extension Wire (T/C): J-Type (WHT) = ( + ), (RED) = ( - ), K-Type (YEL) = ( + ), (RED) = ( - )

     *     Multi-Conductor Sensor Cables; [(BRN) = ( + ), (BLU) = ( - ), (BLK) & (WHT) = Signal]

     *     Multi-Conductor AC (SO Cord or Romex):  (BLK) = Hot & (WHT) = Neutral


Now for the hard part - Power From Another Source (ungrounded Conductors which remain energized when the Main Disconnect is OFF)

     *     Orange (ORG):  [a remnant from the JIC, NFPA-79 (2002) shows (YEL) where (ORG) is called out (2018)


     Industry trend:

     *     White with an Orange Stripe (WHT/ORG);  AC Neutral (even though it's Grounded, it's compliment is still Hot)

     *     (RED/ORG) or (RED/YEL):  120V AC

     *     (BLU/ORG) or (BLU/YEL):  24V DC


Attached is a document recently added to another Question that I thought would be good to break-out with this as a separate discussion. 


Many thanks to all who participate.