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.
Older Type BX cable and EGCs
We ran into a question regarding older Type BX wiring and the Code compliance of using the metal jacket for grounding. Although the Code states that Type AC cable metal jackets can be used as a grounding means, we cannot find if the older version Type BX is also compliant. How would you justify the use of such wiring with the metal jacket as an equipment ground and prove the validity of your argument with Code backing?
The installation and construction requirements for Type AC, “armored cable” are located in Article 320 of the NEC. Many in the industry may still incorrectly refer to Type AC as BX cable. Edwin Greenfield and Gus Johnson developed basic armored cable in the early 1900s. The abbreviation BX has stuck to all metal-jacketed cables for decades. Type AC cable, as constructed today, is a significantly improved product. Section 320.2 defines Type AC cable as a fabricated assembly of insulated conductors in a flexible, interlocked metallic armor. The definition sends the NEC user to Section 320.100, Construction, for information. Type AC cable is required to have an armor of flexible tape with an internal bonding strip of copper or aluminum in intimate contact with the armor for the entire length. This internal, electrically conductive bonding strip, in intimate contact with each wrap of metal armor, is necessary to ensure a low impedance path on the metal jacket to allow it to function as an equipment grounding conductor (EGC). Section 250.118(8) permits the armor of Type AC cable to be used as an EGC in accordance with 320.108, which requires an adequate path for fault current.
Older Type BX cables are not recognized in the NEC today. These cables are not constructed with an internal bonding strip to ensure an adequate path for fault current and are not recognized in 250.118 as an EGC.
Field-applied hazard warnings
On a recent project, we had to revise numerous labels that we applied to electrical equipment as required by the NEC. We like to make our own custom labels that may include multiple marking requirements along with our company name and phone number. During the punch list phase of a recent project, we were informed that our labels did not meet the ANSI standard for product safety signs and labels. The specific labels that were identified as being a problem were the arc flash hazard warning in Section 110.16 and the disconnect location marking required in Section 450.14. The owner took issue with the size of the lettering and colors used in the labels. There are no specific NEC requirements for letter size or colors; there is just an informational note to the ANSI standard. Were we in violation, or is the ANSI standard reference just informational? Why is the NEC silent on the height of lettering and colors used for a specific label?
The requirements in Section 110.21(B) pertain only to “field applied hazard markings.” Where the NEC requires a caution, warning or danger sign to be field applied, the provisions of 110.21(B) must be followed. The marking is required to adequately warn of the hazards using words, colors or symbols. The NEC does not require specific text sizes or colors that would be assigned to a warning and the use of symbols.
The informational note does direct the NEC user to ANSI Z535.4 2011, Product Safety Signs and Labels, which provides guidance for suitable font sizes, words, colors, symbols and location requirements for labels. The NEC cannot feasibly provide the Code user with all of the necessary information to cover every type of label applied in all of the possible installation scenarios, and that is the reason for the reference to the ANSI standard in the informational note. The text size in a warning label and the location are based on many factors including, but not limited to, the intended viewer and to ensure a safe viewing distance. The colors used and backgrounds are also identified in the ANSI standard with specific requirements that include but are not limited to, the word “Caution” in black letters on a yellow background, the word “Warning” in black letters on an orange background and the word “Danger” in white letters on a red background. These colors, while not specifically addressed in the NEC, are universally understood and must be adhered to for field-applied warning labels. Making labels on your own without following these guidelines could subject the label-maker to future liability concerns. The required label in 450.14 is not a field-applied hazard marking, and the requirements of 110.21(B) would not apply. Perhaps a future edition of the NEC could include annex material to provide the NEC user with the necessary information to build custom labels.
Disconnects locked open
Multiple NEC requirements require a disconnecting means to be capable of being locked in the open position. These requirements have been in place for many cycles. Over the last few NEC cycles, text was added to these requirements that mandated that the means to apply the lock must remain in place with or without the lock installed. Now, the new Section 110.25 contains this requirement. Each NEC section that requires a disconnecting means to be capable of being locked in the open position now refers to Section 110.25. What does that really mean? If I am using a fusible disconnect, there is a hole in a metal plate that allows for the placement of a lock. What about a standard two-pole, 30-ampere (A) circuit breaker in a panelboard? Is it permissible to use a lockout/tagout type device that goes over the circuit breaker handle to apply the lock?
No, the use of a portable device that would be placed over the handle of a circuit breaker for applying a lock is not permitted. These devices are not designed to remain in place with or without the lock installed. This type of device must be removed in order to close a panelboard cover and in some cases must be removed in order to remove the panelboard deadfront. In the case of a two-pole 30A circuit breaker, an accessory device must be purchased from the circuit breaker manufacturer and installed over the circuit breaker. All manufacturers of circuit breakers have a line of accessory devices that include a means to apply locks. These devices will be placed over the circuit breaker before the deadfront goes on and will remain in place with or without the lock applied. Larger circuit breakers can be custom ordered with a means to apply a lock installed on the circuit breaker itself.
Type FCC cable in schools?
On a recent project, we had to provide floor outlets for multiple desk stations in a middle school. We submitted plans that included the use of flat conductor cable (FCC). We have never used this product, but the physical layout of the school and 10-inch concrete floors presented a challenge to installing branch circuits on the floor below with standard doghouse-style floor outlets. The plans examiner rejected the use of FCC, citing Section 324.12, which prohibits the use of FCC in a school. Why is there such a prohibition?
The use of FCC as applied to venues is prohibited in schools, residential occupancies and hospital buildings. Essentially, it is limited to use in commercial occupancies. A review of FCC installation requirements provides some insight on the reason for such prohibition. This product is only permitted where the floor coverings (see Section 324.41) are carpet squares not larger than 39.37 square inches adhered to the floor with a special release-type adhesive.
This is to allow access to the wiring method without pulling up wall-to-wall carpeting. The use of this product in a commercial occupancy lends itself well to adding and removing floor outlets on a regular basis. Typically, removable carpet squares are not the type of floor covering applied in residential, school and hospital occupancies. The use of removable carpet squares makes access to FCC easy, as one need only pull up one corner of the carpet square. In schools and residential occupancies, this could lead to easy access by children who pull up the carpet.
About The Author
DOLLARD is retired safety coordinator for IBEW Local 98 in Philadelphia. He is a past member of the NEC Correlating Committee, CMP-10, CMP-13, CMP-15, NFPA 90A/B and NFPA 855. Jim continues to serve on NFPA 70E and as a UL Electrical Council member. Reach him at [email protected].