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.


Previous use of gray conductors


A recent discussion on the job was centered on the use of branch-circuit conductors that are gray in color. We are in an older industrial plant, and there are branch circuits in conduit that include gray-colored conductors that are hot. I have been in the electrical business for more than 30 years and a contractor for 15 years. We have always used the color gray for neutrals in 480/277-volt (V) systems, nothing else. This is a serious safety concern. The maintenance electricians working in the plant have told us that, when those branch circuits were installed, it was permissible to use gray as an ungrounded conductor in conduits. We are confused. Can you help?


For decades, the NEC permitted the colors white or “natural gray” to be used for grounded conductors. The issue here is the term “natural gray,” which was used to address white “code-grade” rubber insulation. When installed, the white conductors had a grayish tint and turned even grayer with age, hence the use of the term “natural gray.” There was no specific prohibition at that time for using the color gray for an ungrounded conductor. Several NEC cycles ago, this became a serious issue, and the technical committee deleted the word “natural.” Colors used to identify grounded conductors in 200.6(A) are now required to be white or gray. You are correct, this is a serious safety issue, and the technical committee recognized the potential confusion on installations such as the older industrial facility you mention. The technical committee added an informational note at the end of Section 200.6 that explains that the color gray may have been used in the past as an ungrounded conductor and care should be taken when working on such systems. While not an NEC requirement, it would be advisable for the plant owner to ensure that all qualified people working in the plant are informed of this previous practice. NFPA 70E requires a documented meeting between the host or building owner and the electrical contractor when the host has knowledge of hazards that may not be evident to the contractor. In this case, the host/owner needs to inform all electrical contractors that conductors that are gray in color may be ungrounded.


Hot and cold water in cable tray?


We are installing a cable-tray system in a retail store. There is no ceiling, and the cable tray is being used to neatly run type MC cable throughout the store for specialty lighting. We have been asked to keep all of our MC cable on one side so that the plumber can use the other side of the cable tray to get hot and cold water to a new bathroom. The general contractor and owner argued that a Unistrut rack is permitted to support more than just electrical conduits, so the cable tray is no different. Does the NEC permit this?


No, Section 300.8 clearly prohibits the installation you describe. Raceways and cable trays that contain electrical conductors are not permitted to contain any pipe or tube for steam, water, gas, drainage or any service other than electrical. The cable tray cannot contain the plumbing. While the NEC may not specifically address such an installation on a Unistrut rack, it clearly prohibits this type of installation in cable tray.


Effectively close those mounting holes?


An inspector recently cited me on a job and required that I “effectively close” the mounting holes on the back of panelboard cans. The installation was exposed in a machine shop and mounted on Unistrut with the back accessible. There were four panelboards along with multiple starters and industrial control panels. I did not use the holes provided in the cans for support. We drilled new holes to match the installation. I had to go back and put machine screws and washers to cover each mounting hole in the panelboards. He told us that, since the mounting holes were larger than ¼-inch in diameter, they had to be closed. I installed a dry-type transformer with vents that large on the same job. It was easier to do what he wanted than to argue with the inspector. I have never seen this before. Does the NEC require those holes be covered?


No, the NEC does not mandate closing holes for support that are not used. However, the general rule in Section 110.12(A) requires unused openings to be closed. This is directed toward unused openings for cables or conduits. The requirement clearly states holes intended for the operation of the equipment, those intended for mounting purposes, or those permitted as part of a listed design are not required to be closed. A panelboard cabinet or switch enclosure may have holes designed for mounting that are not used. The NEC does not require them to be closed. While it may be easier to appease the inspector when you believe he or she is incorrect, it is always advisable to engage in discussion. Ask them to help you understand by showing you the applicable requirement in the NEC.


Feeder-tap equipment 
grounding conductors


In an older, 21-story commercial building, we are replacing very old panelboards as part of a complete renovation of the tenant floors. The panelboards are of different ratings but all fed with feeder-tap conductors. The feeders are fed from circuit breakers in the gear room and are rated 200 through 600 amperes (A). The length of each set of taps is, in almost all cases, less than 10 feet, with none over 20 feet. The drawings require the correct size ungrounded conductors in accordance with the 10- and 25-foot feeder-tap rules in Section 240.21. The problem is that the equipment grounding conductors (EGCs) are sized based on the overcurrent protective device (OCPD) that the feeder taps terminate in and not on the size of the OCPD protecting the feeder. We brought this up to the general contractor and received a letter from an electrical engineer stating that he did some calculations and the EGCs as required were fine. We disagree. What should we do?


You are correct. Section 250.122(G) requires an EGC run with feeder-tap conductors to be sized not smaller than that required for the rating of the feeder OCPD. This requirement does not include permissive text to allow an engineering evaluation to determine minimum size. The OCPD in which the feeder taps terminate provides overload protection for the tap conductors only, and the OCPD protecting the feeder protects the tap conductors in a short-circuit or ground-fault situation. The EGC installed with the feeder taps must be sized to handle the fault current supplied through the feeder OCPD and provide a low impedance path to facilitate the operation of the OCPD. The engineer must discuss this with the electrical inspector. Section 90.4 allows the inspector to waive specific requirements where equivalent objectives are achieved for safety. This would have to be in writing from the inspector and is very unlikely for several reasons. There are just too many variables including, but not limited to, the value of available fault current used, the type of circuit breakers protecting the feeders, and the maintenance and history of the circuit breakers. The future of the installation and possible replacement of the feeder OCPDs must also be considered.


Splice in a panelboard?


The same argument comes up on many jobs when a pull ends up a little short and the conductors will not reach the neutral bus or circuit breaker. Is it permissible to splice in a panelboard?


The answer to your question begins with the definition of “panelboard” in Article 100. A panelboard is typically made up of bus and OCPDs; it is designed to be installed in a cabinet or cutout box and is only accessible from the front. The splices you mention are not made in the panelboard. They are in the cabinet or cutout box. Section 312.8 permits splices in enclosures that contain OCPDs, provided the maximum conductor fill provided is not exceeded.