Jim Dollard has an extensive background in codes and standards. Send questions about the National Electrical Code (NEC) to Jim at [email protected]. Answers are based on the 2023 NEC.

Testing GFCIs

We recently received an OSHA citation for not being able to document GFCI receptacle testing in our temporary wiring. The temporary wiring is installed in accordance with Article 590 in the NEC, and we cannot find such a requirement.

Article 590 does not contain a GFCI testing requirement. Perhaps it should and you can submit a public input to get that done. However, see Section 90.3, which instructs the reader on the NEC’s arrangement. Article 590 contains only supplemental requirements and modifications of general requirements for temporary wiring. All of the NEC applies to temporary wiring unless modified in Article 590.

OSHA does not use the NEC when performing an inspection of temporary wiring. The citation you received is likely from the OSHA 1926 construction standard. The applicable OSHA requirement is in 1926.403(b)(2) and mirrors the NEC requirement in Section 110.3(B) for installation and equipment use. 

Each requirement mandates that all listed, labeled or identified (OSHA includes certified) electrical equipment be installed and used in accordance with any instructions included in the listing, labeling or manufacturer’s instructions. It is typical for GFCI manufacturers to require monthly testing. This is where OSHA steps in and may request to see documentation of the required testing. Remember, if you do not document testing, in OSHA’s eyes, it did not happen. Unfortunately, this is a common citation issued to ECs. I suggest you build a simple table in document form and have an apprentice test and document all GFCI devices at the beginning of each month.

Cable tray permitted?

The installation of a new switchboard in an older structure being repurposed as condos gave us fits with respect to getting feeders installed. The option we chose was to penetrate the concrete deck with 4-inch EMT and then into a cable tray to the switchboard. The conductors are larger than 1/0 AWG but the inspector failed the installation. Section 392.10 states cable tray is not limited to industrial establishments. This must be a new requirement! Can you help?

As stated in your question, Section 392.10 provides permitted uses of cable trays and clarifies that it is not limited to industrial installations. This section also states that single-insulated conductors are permitted in cable trays only when installed in accordance with 392.10(B)(1). 

While that sentence was added in the 2020 NEC, it was to add clarity only. Previous editions very clearly prohibited single insulated conductors in other than industrial establishments. A cable tray is not a wiring method—it is used to support. A condominium is not an industrial establishment. While the NEC does not define industry, standard definitions clarify that to be industrial, raw material is brought in and finished products are created. In an occupancy of the type described in your question, a cable tray is permitted, but it can only contain the wiring methods listed in Table 392.10(A). It is important to note that single insulated conductors are not listed in that table.

Individual branch circuit receptacle

Engineered electrical drawings required (30) 20A, 120V branch circuits supplying a single duplex receptacle at work stations. We installed a single 15A, 125V duplex receptacle for each branch circuit as required in the drawings. The general contractor’s representative is requiring us to replace the 15A duplex receptacles with 20A duplex devices, claiming it is a Code requirement. Is that correct?

No, the 15A duplex receptacles are Code compliant. There is no such thing as a “dedicated” branch circuit in the NEC. An individual branch circuit as defined in Article 100 supplies only one utilization equipment. That could be a hard-wired condensing unit in a dwelling unit or a single receptacle (one contact device on a yoke) for a Level 2 EV charger. The branch circuits in your question are not individual branch circuits.

The NEC requirement that the GC is referring to is in Section 210.21(B)(1), which mandates that a single receptacle installed on an individual branch circuit must have an ampere rating not less than that of the branch circuit. A duplex receptacle is not a single receptacle. The definition of receptacle in Article 100 clears up this misconception. A receptacle is a contact device installed at the outlet for the connection of an attachment plug. No specific appliances or loads were referenced.

A single receptacle is a single contact device with no other one on the same yoke or strap. A multiple receptacle is two or more contact devices on the same yoke or strap. The associated informational note (following the definition of receptacle) provides clarity for the Code user, stating that a duplex receptacle is an example of a multiple receptacle that has two receptacles on the same yoke or strap. It is important to note that the requirements of 210.21(B)(3) for receptacle ratings also apply in this case. See Table 210.21(B)(3), which clearly permits a 20A branch circuit supplying more than one receptacle (two receptacles in this case on the same yoke) to supply 15A or 20A devices.

Relocated panelboard

In a commercial/retail occupancy, a new tenant wants to relocate a 208/120V panelboard. Each tenant has a 480V feeder. The owner wants to relocate the panelboard but not the ceiling-mounted transformer supplying the panelboard. The secondary conductors will be about 75 feet long. Is that OK? If needed, could we mount a circuit breaker enclosure above the lay-in ceiling?

The maximum length of transformer secondary conductors in this situation is 25 feet; see 240.21(C)(6). Adding a circuit breaker enclosure above the ceiling is not permitted to comply with the requirements of 240.21(C). The general rule in Section 240.24(A) requires that the center of the grip of the operating handle of the circuit breaker, when in its highest position, is not more than 6 feet, 7 inches above the floor or working platform, unless one of four permissive applications apply: (1) for busways in 368.17(C), (2) for supplementary overcurrent protection in 240.10, (3) for overcurrent protective devices (OCPDs), in 225.40 and 230.92 and (4) for OCPDs adjacent to the utilization equipment they supply. A practical solution would be to move the transformer close to the relocated panelboard.

Service or outside feeders

Where a large campus-style facility generates its own power at 13.2 kV, 24/7 all year long, it is our opinion that rules in Article 230 for services would apply. Is that correct?

No, the term service in the NEC includes only the conductors and equipment connecting the serving utility to the wiring system of the premises served. See the definition of “service” in Article 100. In this situation, the generation equipment and distribution to individual structures on the campus are privately owned, as no electric utility exists. Article 225 requirements for outside feeders and branch circuits apply. Note that these rules are very similar to those found in Article 230 for services.

New products?

Can you give an example of how new products that may not be commercially available are handled in the Code?

It is typical for the technical committees revising the NEC to build in a delayed implementation date when a new requirement is added with a significant effect on products that may not be readily available. 

One example is the requirement for arc energy reduction where fuses rated 1,200A or larger are installed. This requirement was new in the 2017 NEC and included a sentence in the parent text that delayed implementation until Jan. 1, 2020. This gave the manufacturers a window to develop and make fused switches to include a means of arc energy reduction. Also see Section 90.4(D), which allows the authority having jurisdiction to permit the use of products, constructions or materials that comply with the most recent Code edition where a new product may not be available.

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