Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Questions can be sent to [email protected]. Answers are based on the 2014 NEC.


Branch-circuit markings


Some local jurisdictions in our area have required type AC/MC cable to be marked externally with a color code to identify as high-voltage 480/277-volt (V) or low-voltage 240/120V. I have seen industry-wide identification of fire alarm AC cable (externally identified “red”) but not branch circuits. Is this being addressed currently, or will it become a requirement? If we use cable marked externally with a color code, are we permitted to re-identify the conductors if needed to comply with 210.5(C)(1)?


The NEC does not require identification marking on the outside of cable assemblies or raceways to identify the color or conductor voltage within. I am not aware of any action to require such markings. If the NEC were to go down that road, it would be necessary to include all cable assemblies and raceways.


The manufacturers of metal-jacketed cable assemblies offer many variations to suit individual installation needs. One option is marking the outer jacket with colors to identify the colors of the conductors in the cable and voltages. While the NEC does not contain a required color code for voltage marking, the industry standard is 208/120V (A) black, (B) red, (C) blue and grounded/neutral white; 480/277V (A) brown, (B) orange, (C) yellow and grounded/neutral gray. Manufacturers may mark the cable assembly outer jacket to identify the conductor colors inside the cable based on the number of conductors in the cable. For example, a four-wire, multiwire branch circuit may be marked with all of the associated colors while a two-wire branch circuit may be marked as blue and white for 120V or yellow and gray for 277V. 


Section 210.5(C)(1) requires multi-wire branch circuits to be marked at termination, connection and splice points. The intention is to identify the voltage where there is more than one nominal voltage system in the building, such as having both 208/120V and 480/277V systems. Using color-coded cable assemblies helps the installer comply with 210.5(C)(1) because the conductors within are easily identifiable by color. However, color-coding the outside of a wiring method is not an NEC requirement. The Code permits the use of marking tape on conductors at terminations, connections and splice points [see 210.5(C)(1)(a)].


Some manufacturers identify voltage levels with color coding in their literature. This has led to confusion where an inspector may reject re-identification of a color-coded cable assembly and base the rejection on Section 110.3(B). I understand the inspector’s reasoning, and in my opinion, the NEC needs to address this. However, we must fully understand that 110.3(B) requires installation in accordance with the product “listing and labeling.” For example, the UL White Book identifies Type MC as “PJAZ,” and there are no limitations or prohibitions in the listing for conductor re-identification. In addition, I have never seen Type MC cable labeled with a prohibition on conductor re-identification. Local requirements as mentioned in your question may take precedence over the NEC and prohibit re-identification.


School receptacles


Are tamper-resistant (TR) receptacles required in K–8 schools?


No. TR receptacle requirements in the 2014 NEC are limited to dwelling units, guest rooms/suites in hotels/motels, and childcare facilities. There are changes on the way for the 2017 NEC (if they make it through the NFPA process) to add preschools; elementary schools; areas in medical, dental and outpatient facilities; and some assembly occupancies.


Is self-certification acceptable?


I am aware that the NEC requires lighting fixtures to be listed. We do retail work that includes restaurants and specialty stores where it is common for the owner to supply some or all of the lighting fixtures. For that reason, we clearly state in our contract that all owner-supplied lighting fixtures must be listed, or we will not install them. An owner recently supplied us with manufacturer literature for custom, 120V, pendant-type fixtures, and the literature states the fixtures “meet the applicable UL standard for luminaires.” Is this acceptable? Should the inspector recognize the manufacturer literature as compliance with the listing requirement?


A manufacturer’s statement on a carton/box, instructions or any type of literature that meets an applicable standard does not mean the product is listed. A product will only be recognized as “listed” where it bears the listing agency’s mark and any other markings that the applicable product standard requires. Where the NEC requires equipment to be listed, manufacturer or owner self-certification in lieu of third-party product listing does not comply with applicable NEC requirements. It is a good practice to inform owners that supply their own equipment that only listed luminaires will be installed and that manufacturer or owner self declaration does not equate to listing.


Grounded conductor terminations


Why does the NEC not permit more than one neutral conductor under a single screw on a terminal block that clearly permits more than one conductor to be terminated under a single screw?


The requirement that you are referring to applies only to panelboards. Section 408.41 is located in “Part III Panelboards” of Article 408, and the general rule clearly prohibits terminating a grounded conductor in an individual terminal that is used for another conductor. This includes equipment grounding conductors that may be terminated on the same terminal strip in service equipment. This installation requirement ensures that, where there is a need to do justified energized work and a grounded/neutral conductor is removed, it is the only conductor under that screw.


For example, if two branch circuits have neutral conductors terminated under the same screw and one needs to be removed, both circuits must be de-energized or serious hazards will occur where the grounded/neutral conductor of an energized circuit is removed. Equipment may also be damaged where a multiwire branch circuit’s grounded/neutral 
conductor is removed while the branch circuit is energized.


Cable tray listing and bonding


The designing engineer on a new project requires the cable tray for a communications system to be listed and bonded. I understand that the cable tray system needs to be bonded. The engineer claims that all raceways containing communications circuits must be listed. That is not an issue because the cable tray system we are installing is listed. Does a cable tray installation that contains only communications circuits need to be listed? How would we size the bonding jumpers where there are separations in the cable tray for communications circuits?


There are no requirements in articles 392 and 800, or elsewhere in the NEC, that would require cable tray to be listed. Section 800.182 requires communications raceways and cable routing assemblies to be listed, not cable tray. 


A common misunderstanding throughout the industry is that cable tray is a raceway. It is instead a support system for raceways, conductors, cable assemblies and cable. Section 392.60(A) requires metal cable tray containing only nonpower conductors to be electrically continuous through approved connections or the use of a bonding jumper. In this application, the cable tray is not being used as an equipment grounding conductor. The only requirement is for the tray to be electrically continuous. The NEC does not have prescriptive requirements for sizing the bonding jumpers for cable tray containing only nonpower conductors.