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 firstname.lastname@example.org. Answers are based on the 2014 NEC.
Incident energy labeling requirements
During the final stages of a large electrical installation in a new hospital, the owner informed us that we needed to label all of the switchboards, panelboards and other equipment with incident energy values in addition to the arc flash hazard warnings we had already applied. We used standard labels that meet the applicable ANSI requirements and Section 110.21, but the owner’s engineer insisted that NEC Section 110.16 requires the warning label to be applied and that Informational Note No. 1 provides guidance on the required information in the label. The engineer told us that we needed to follow the guidance provided in the informational note, which refers to NFPA 70E, and then provide “arc flash labeling” accordingly. We disagreed, and our electrical inspector supported our position. We always strive to meet NEC requirements and to do the best job for our customer, but this customer became upset with us over this labeling issue.
The owner’s engineer was incorrect, as the NEC does not require labeling of incident energy values. Section 110.16 requires specified equipment to be field- or factory-marked to “warn qualified persons of potential electric arc flash hazards.” Informational notes in the NEC are not mandatory, and they are not enforceable, according to 90.5(C). The reference to NFPA 70E is included as nonmandatory text to inform the user that there is a recognized industry standard for electrical safety in the workplace. NFPA 70E does not contain any installation requirements, as it is a work practices standard. If the facility owner chooses to do so, he or she can implement the arc flash labeling requirements in NFPA 70E as part of an electrically safe work practices program.
Over the last several NEC revision cycles, there have been many proposals to require incident energy labeling in 110.16. Each attempt to include labeling of incident energy in 110.16 has failed. Perhaps, a future public input to revise the NEC will require detailed labeling in all new installations.
Heavy-walled plastic junction boxes as handhole enclosures
Can I use heavy-walled, 12-by-12-inch plastic junction boxes as handholes? I have long runs of ¾-inch PVC conduit underground to supply security lighting on the perimeter of a large property, and the only load that could be put on the boxes would be a riding lawn mower.
No. Section 314.30 requires that handhole enclosures be capable of withstanding all loads imposed on them. A standard junction box and cover is not rated to handle any weight at all. Handhole enclosures are required to be identified for use in underground systems, and the cover must have an identifying mark or logo. In this case, the identifying mark or logo must be electric. You will need to use handhole enclosures identified for direct burial with “electric” marked on the cover.
Grounding and bonding metal-sheathed buildings
I am working on several stand-alone structures for a local municipality. There is no structural steel. The projects are wooden structures with metal roofs and metal sheathing on concrete pads. Most of these structures have only lighting and a few receptacle outlets, since they only will be used to house equipment for snow removal and other projects. There are a few others that will have additional branch circuits for performing limited maintenance. Am I required to bond the metal sheathing to the grounding electrode or an equipment grounding conductor (EGC)?
There is no NEC requirement to ground or bond the metal sheathing on the structures described. Article 250 is separated into parts to logically separate requirements. Part III provides requirements for grounding electrode systems, and 250.52 recognizes under given conditions a “metal frame” of a building or structure as an electrode. In Part V for bonding, 250.104(C) requires “structural metal” of a building or structure to be bonded under given conditions. In Part VI for equipment grounding, metal sheathing is not required by 250.116 to be connected to an EGC. It is important to note that these requirements address metal frames and structural metal of buildings/structures, not metal sheathing. There is an informational note below 250.116 that provides guidance on this issue. The note explains that, where there is “extensive metal in or on buildings” (such as metal sheathing) and this metal may become energized and is subject to contact by people, bonding and grounding will provide additional safety.
Electrical system maintenance and supervision
In the plan review stage for an addition to a manufacturing facility, we were asked to provide documentation to ensure that people maintaining and supervising the electrical installation are qualified. The facility includes a foundry and machines to produce a wide array of products, primarily pump housings. The reason for the question about qualified people is that the electrical design includes transformer secondary conductors installed in accordance with 240.21(C)(3) for industrial secondary conductors not longer than 25 feet. How can we provide documentation of qualifications for people we don’t employ?
Numerous requirements in the NEC demand specific conditions of maintenance and supervision of the electrical system. This is included in the NEC to ensure that only qualified people service the system. Requirements tied to conditions of maintenance and supervision are essentially industrial exceptions. These requirements are easily applied in large industrials such as major car manufacturers. For smaller facilities, this can be problematic for the electrical contractor and the inspector.
There are many serious challenges here. The limited information provided in your question is descriptive of an industrial installation. However, there is no NEC definition of the terms “industrial” or “industry,” forcing the contractor and inspector to make the call.
Only the facility owner can provide documentation of qualifications for people maintaining the electrical system, and the contractor can provide that information during plan review. This can be done with documentation of qualified staff in the owners’ employment or through an exclusive agreement that only qualified electrical contractors will service the system. Where permissive NEC requirements based on conditions of maintenance and supervision are used, it is important for the contractor to have the owner document how they will ensure that only qualified people service the system.
The local transit authority has specified type RTRC-XW conduit on a rail yard expansion. We know that RTRC is reinforced thermosetting resin conduit. What does the suffix XW require?
Section 355.10(F) permits type RTRC conduit to be exposed if it is identified for such use. An informational note below that section explains that the suffix “XW” identifies the conduit as being recognized for use in areas where it is subject to physical damage.
Thermal insulation and LED luminaires
We are in the middle of a project to replace some lighting in multiple grocery stores in our area. The project involves replacing existing fluorescent 2-by-2 lay-in-type luminaires. The new luminaires are light-emitting diodes (LEDs). The electrical inspector issued us violations because the fixtures are not Type IC; they are not identified for contact with thermal insulation. I do not understand why we were issued a violation or why LED luminaires would need to be IC-rated.
The NEC requirement for recessed luminaires and contact with or proximity to thermal insulation is not based on the type of luminaire. Where any part of a recessed luminaire is in contact with or within three inches of thermal insulation, it must be identified as Type IC. The requirement is not based on the amount of heat created or the type of luminaire. Where thermal insulation is installed above a recessed luminaire or within 3 inches of its enclosure, wiring compartment, ballast, transformer, LED driver or power supply, Section 410.116(C) clearly requires that the luminaire must be identified as Type IC for insulation contact.