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Conductor Identification and Grouping

By D. Jerry Flaherty, Chief Electrical Inspector, Electrical Inspection Service Inc.

(631) 286- 6642             



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

Thank you. 

Aluminum Wiring
Aluminum wiring installed in homes in the 1960’s and early 1970’s can be problematic. In the early 70’s the U. S. Consumer Products Safety Commission (CPSC) conducted an investigation that determined that a house wired with aluminum is 55 times more likely to have branch circuit receptacles or switches reach a fire hazard threshold than houses wired with copper wiring. This investigation noted the issues with aluminum wiring are:
Aluminum Wiring.pdf
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Cables NM AC MC
Uses permitted, not permitted, and supporting cables
By D. Jerry Flaherty, Chief Electrical Inspector, Electrical Inspection Service Inc.
One of the most confusing areas we have is what type of cable can be used in different locations and what the limitations of the cable are. I get several calls a week on cables and often end up looking up the information. The table below is based on both the National Electrical Code and the Residential Code of NYS.
Cables NM AC MC.pdf
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Electrical Safety after Sandy
A lesson learned from Katrina is that the storm water after the hurricane can be as dangerous as the hurricane itself. Storm water from Hurricane Sandy that contaminated most homes on Long Island is salt water and can also contain sewage, septic runoff, gasoline, oils, insecticides, fertilizer, and a host of other pollutants, contaminants and corrosive material. Storm water is a health hazard, a fire hazard and is very corrosive. Energizing a building that is or was submerged in storm water can lead to electric shock, electrocution or fire. Wiring and electrical equipment that has been dried can still be dangerous, the film left by the storm water can be still be conductive, corrosive and lead to black mold. Extreme caution should be exercised when working with electricity in or near storm
Electrical Safety after Sandy.pdf
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Electrical Wiring in Flood Zones
The Building Code of New York State requires that “all electrical systems, equipment and components” be installed to avoid damage from flooding [RR324.1.5]. The minimum height of electrical systems and equipment is determined by the design flood elevation (DFE) plus two feet freeboard [RR324.1.3.3]. If the DFE is five feet then the minimum mounting height is seven feet.
Electrical Wiring in Flood Zones.pdf
Adobe Acrobat document [69.1 KB]
Flood Damaged Electrical Equipment
New York State division of Code Enforcement has issued a Technical Bulletin titled “Electrical Systems and Equipment in Flood-Damaged Structures”. Technical Bulletins are amendments to the NYS Building Code and must be adhered to. This Technical Bulletin (TB) addresses several important issues that we face after Hurricane Sandy however, the TB did not address the corrosive effects of salt water that inundated the North and South shores of Long Island. Below is a summation of the TB.
Flood Damaged Electrical Equipment.pdf
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NEC Requirements for Optional Standby Generators
Since superstorm Sandy we have seen hundreds of generators installed on Long Island. I have inspected many of these systems and answered lots of questions about generator installations. This article covers the more frequently asked questions and is not all inclusive. There are many other issues that can arise when installing generators; calling your inspector to discuss the installation and attending a course on generator installation is strongly suggested.
NEC Requirements for Optional Standby Ge[...]
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Standby Generators
Since tropical storm Irene I have received 50 calls on how to connect whole house generators. These generators are “Optional Standby System” generators as outlined in Article 702. If the (automatic) transfer switch (TR) is installed immediately after the electric meter it must be a service rated transfer switch that will have a service rated disconnect and OC, usually a circuit breaker. The first disconnect on the service conductors is the service disconnect; all conductors after the service disconnect are feeder conductors. All bonding and grounding must be done at the service disconnect (transfer switch). There are two scenarios; 1) The existing service equipment and the transfer switch are located on or in the dwelling and 2) the electric meter and the transfer switch are remote (no
Optional Standby Generators 2008 NEC.pdf
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Sizing Electric Transformers
A transformer installation can be a mind boggling experience with code requirements in many different NEC articles. In this article I hope to summarize the NEC requirements for typical dry-type transformer.
Sizing Transformers: A transformer must be sized to satisfy 100% of the load connected to the transformer. Article 220 should be used to calculate the transformer load. The load should be evenly distributed across the phase. To calculate the minimum transformer kilo-volt-amps (kVA) use the following;
Sizing Electric Transformers.pdf
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Wiring Doctors, Dentists and Similar Facilities
One of the fastest growing industries on Long Island and through the Nation is health care. Doctors and Dentists office, urgent care, and dialysis facilities are opening as standalone buildings and in shopping centers. Understanding the “National Electrical Code” [NFPA 70] (NEC) Article 517 and “Standards for Health Care Facilities” [NFPA 99] are the foundation to knowing how to wire these facilities for the safety of the patients as well as those that administer care of the patients who use these facilities. Both of these standards regulate facilities from the small office a doctor might have in his home for patients care to mega medical centers; both of these standards are also very complicated and use terms that we are not at all firmilure with.
Wiring Doctors, Dentists and Similar Fac[...]
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