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.

Floating buildings

What wiring method is required to supply floating buildings? We have drawings that detail new service equipment on land approximately 100 feet from four floating buildings that will each be feeder-supplied. A note states that “approved flexibility” is required. What is that?

Floating buildings supplied by service or feeder conductors must maintain flexibility with the supply conductors. Section 555.52(A) requires the installation to ensure that motion of the water surface and changes in the water level will not result in unsafe conditions. This can be achieved through the use of liquidtight flexible metal conduit or liquidtight flexible nonmetallic conduit with approved fittings. Portable power cable is also permitted, provided that it is listed for extra-hard usage, wet locations and sunlight resistance. Chapter 3 raceways suitable for the location are permitted where flexibility is not required. It is important to note Section 555.53 requires each feeder overcurrent protective device (OCPD) supplying floating buildings be provided with ground fault protection that does not exceed 100 mA, or an alternate method is to provide ground-fault protection of all feeders and branch circuits.

Concrete-encased electrodes

Where a connection is made to a concrete-encased electrode, do we need to drive two ground rods? There is no metal underground water pipe and the building is wooden.

The requirement in Section 250.50 is to install a grounding electrode system that must include any and all of the electrodes listed in 250.52(A)(1) through (A)(7). Based on your question, the only grounding electrode that exists is the concrete-encased electrode in 250.52(A)(3). It is not required to install ground rods to supplement the concrete-encased electrode. See 250.53(D)(2) that requires a metal underground water pipe to be supplemented by an additional electrode. The supplemental electrode is required here because a metal underground water pipe may be replaced by plastic. A concrete-encased electrode can stand alone as a grounding electrode.

Separate emergency power service

The facility we are in has a separate service on the opposite end of the building for emergency power. Is that permitted? If so, in the future, can we just tap ahead of the service disconnect in the same manner as a fire pump source?

A separate service is permitted as a fire pump source. The key word here is “separate.” You cannot have a single service tap ahead of the service disconnect and then claim that as a separate service. It must be a separate utility circuit, preferably supplied from a different substation. Requirements for emergency system sources of power are located in Part III of Article 700. Section 700.3(F) permits a separate service provided it is approved by the AHJ. This requires the electrical inspector to determine the reliability of this source by evaluating the utility sources and ensure that the requirements in 700.12(F) are applied.

Where a separate service is used as an emergency source, it must be installed in accordance with Article 230 requirements and requires separate overhead service conductors, service drops, underground service conductors or service laterals. The service conductors for the separate service must be installed sufficiently remote electrically and physically from the service supplying normal power to the structure. This is done to ensure that first responders do not open both service disconnects in the event of emergency. It is typical and prudent for the electrical inspector to request additional signage at the location of both services supplying the structure to inform installer/maintainers and first responders that a separate service is the emergency system power source.

Marking for fire alarm systems

An electrical inspector wanted us to add red labels/stickers onto the circuit breaker supplying a small fire alarm system. We were told it is a Code requirement. Is that new? Do we need the red marking in homes for 120V smoke detectors?

No, this is not a new requirement. See Section 760.41(B), which requires more than just red identification for the branch circuit OCPD supplying the fire alarm system. In addition to red identification, the OCPD must be identified as “FIRE ALARM CIRCUIT.” The branch circuit supplying the fire alarm system is not permitted to have AFCI or GFCI protection. This requirement applies only to fire alarm systems and does not apply to 120V smoke alarms.

Lighting and switches in 517.13

In a hospital, does the lighting and switching in patient rooms have to be installed per 517.13? Do we need the redundant grounding for this equipment? We have been given multiple different answers and are quite confused.

The answer to your question is found in the parent text and the associated exception of Section 517.13. An understanding of applicable defined terms in Article 100 is essential to properly apply this section. The requirements for a metal raceway system or a cable having a metallic armor or sheath assembly (517.13(A)) and an insulated copper (517.13(B)) equipment grounding conductor (green) installed with the branch circuit conductors are required in “patient care spaces” as defined in Article 100. A patient care space is any space of a healthcare facility wherein patients are intended to be examined or treated. A healthcare facility (Article 100) is a building, portions of buildings or mobile enclosures where human medical, dental, psychiatric, nursing, obstetrical or surgical care is provided.

The exception in the parent text of 517.13 permits luminaires more than 7 ½ feet above the floor and switches located outside of the patient care vicinity to be connected to an equipment grounding return path complying with the requirements of 517.13(A) or (B). The patient care vicinity (Article 100) is a space within a location intended for the examination and treatment of patients, extending 6 feet beyond the normal location of the bed, chair, table, treadmill or other device that supports the patient during examination and treatment and extending vertically to 7 ½ feet above the floor. Provided the ceilings in your healthcare facility are 7 ½ feet or higher above the floor, and all switches are more than 6 feet from the beyond the normal location of the bed, chair, table, treadmill or other device that supports the patient, the provisions of 517.13(A) or (B) may be applied.

‘Applicable industry practice’

I am confused by the revised requirement in 110.16(B) for applying an arc flash label. What does it mean by applicable industry practice? Does that mandate that I use a particular method or software program?

Section 110.16(B) requirements are significantly modified in the 2023 NEC. As revised, this labeling requirement is expanded to include equipment supplied by services and feeders. Additionally, the threshold for labeling is expanded to include all equipment rated 1,000A and higher (a reduction from 1,200A). The previous requirement (2020 NEC) mandated labeling the nominal voltage available fault current at the service OCPD, the clearing time of the service OCPD and the date the label was applied.

As revised, this requirement mirrors the exception in previous Code text that allowed equipment labeled in accordance with acceptable industry practice. See Informational Note No. 2 that informs the Code user that “acceptable industry practice” can be found in NFPA 70E-2021, Standard for Electrical Safety in the Workplace. This allows a label in accordance with NFPA 70E Section 130.5(H). This requirement recognizes the incident energy analysis method and the arc flash PPE category method. It is important to note that while NFPA 70E Section 130.5(H) does not require the date on the label, NEC Section 110.16(B) does require it to be applied. Arc flash labels must meet the requirements of 110.21(B).

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