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Conductor Identification and Grouping
By D. Jerry Flaherty, Chief Electrical Inspector, Electrical Inspection Service Inc.
(631) 286- 6642 WWW.EISLongIsland.com
The 2011 and 2014 NEC have several changes for grouping and identifying conductors. Below is an overview of these changes.
200.7(c)(1) Reidentifying of White/Gray conductor – The NEC requires that when using a cable as a switch leg or traveler between switches that the white or gray wire be the supply or hot wire and to be reidentified. Ex -If there is a two wire cable from a ceiling box (supply) to a switch, at the ceiling box the white wire in the switch leg would be connected to the supply and identified as the supply by a black tape or some other method and the black wire in the switch leg is connected to the light. At the switch the white wire would also be identified as the supply by black tape or some other method.
Identification and grouping of conductors- Chapter two of the NEC has several requirements for the neutral or grounded conductor (200.6), the phase or ungrounded branch circuit conductors (210.5), the phase or ungrounded feeder conductors (215.12) and also DC ungrounded conductors. Although the requirements are in different sections of the NEC, the requirements are the same and will be addressed as such.
Grounded conductors (Neutrals)- The NEC requires that where there are neutrals from different systems, 208/120 volt and 480/277 volts, that the neutrals be distinguished from each other where the neutrals are in the same box, enclosure or raceway. The NEC offers several options to distinguish the neutrals providing that the neutrals are white or gray. The trade standard is a 208/120 volt system is white and 480/277 volt is gray.
Ungrounded conductors (Phase conductors) – The NEC also requires that where there are branch circuit or feeder phase conductors from different nominal voltages, 208/120 volt and 480/277 volts, that the phase conductors be distinguished from each other. Again the NEC offers several options to distinguish the phase conductors. The trade standard for 208/120 volt is black, red and blue and for 480/277 volt brown, orange and yellow. This requires that each phase conductor from the service to the final outlet be identified by phase. Ex. If a receptacle in an office is on the “C” phase let’s say, the blue phase, at the service then receptacles hot wire must also be identified blue. If a two wire cable is used then the black wire can be taped blue.
Posting of Identification- The NEC also requires that the identification method be posted on each panelboard or similar equipment.
DC Ungrounded Conductor – The NEC also require all ungrounded positive feeders and branch circuits (strings) be red and all ungrounded negative feeders and branch circuits (strings) be black. If the system is a grounded system then the grounded conductor still has to be white.
Grouping – The NEC requires that multiwire branch circuits and enclosures with more than one neutral be grouped or identified in each enclosure. If there is 2 two wire cable entering a box through a duplex connector then the black and white for each circuit have to be grouped or identified in some manner. In a PV system with several strings (branch circuit), each string has to be grouped or identified. Grouping can be done with cable ties, taping together or some other method while identifying can be numbers some or other method.
Please send any comments, questions or suggestions to JerryFL@optonline.net