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.

Does Article 680 apply?

We are helping out on a church that includes a storable baptistry pool. Is that covered by Article 680? Our concern is the requirements of 680.26(B)(2) and the location of the perimeter surface bonding. This pool sits on the finished floor and may be in a slightly different spot each time.

Yes, a baptistry pool is an immersion pool, as defined in Article 100. These pools are used for ceremonial or ritual immersion of users and are designed to have the contents drained or discharged. Part III of Article 680 includes requirements for storable pools, spas, hot tubs and immersion pools. Section 680.30 requires a storable immersion pool to comply with Part I and Part III of Article 680. The requirements for perimeter surface bonding are in Part II and would not apply.

Emergency natural gas generators

I have been engineering emergency systems for over 20 years and have used natural gas generators on many installations. A plan review just shot down my design stating that dual fuel supplies are required. Why? I don’t get it. This is an overreach!

The fact that you designed emergency systems in the past with a natural gas generator and it was not flagged by the municipality or township does not justify a future installation. Emergency systems are installed for life safety. It is critical that the source of power be capable of supplying equipment necessary for life safety and egress during the period of the emergency. For that reason, Section 700.12(C) requires the emergency power source to be capable of two hours of system operation. Where the emergency system is necessary to supply only illumination, unit equipment is permitted. Where a generator is used as the standby source for the emergency system, the on-site fuel supply must be sufficient for not less than two hours of operation; see 700.12(C)(1). 

Section 700.12(C)(3) does not permit a standby generator as an emergency source to be solely dependent on a public utility gas system for the fuel supply. There is an exception that allows the AHJ to permit a public utility gas system as the sole source of fuel where the AHJ determines there is a low probability of the loss of electric utility power and the public utility gas system. In most cases, that is unlikely to occur because, in a fire situation, first responders will cut off electrical power and natural gas supply to the building or structure involved.

EMT in parking garage

Is EMT with set screw couplings and connectors permitted in a parking garage? It is all-concrete, and we will be running it up tight against the overhead deck. There are no windows, just openings to outdoors. We are not anywhere near the outdoor edge of the garage. There are some in the office that argue it is a wet location and compression couplings are required. Is that right?

No, see Section 358.42, which requires that couplings and connectors used with EMT comply with 314.15 where the installation is a wet location. The installation you described in your question is not one if it remains as is. It is protected by the structure above and is not exposed to rain or snow, which means it is not subject to saturation. In this installation, the EMT is in a location protected from rain. Some locations in the installation may be subject to moderate degrees of moisture and would be a damp location. Set screw couplings and connectors would be permitted. 

Ground a transfer switch?

On a recent project that involved the installation of a 480/277V standby generator for emergency power at an existing warehouse, the designer requested we install grounding electrode conductors from the neutral terminations in the new transfer switch to building steel and ground rods. The designer claimed that the generator needed to be grounded, which was his preferred method. There was only one transfer switch, and it was 3-pole. Was the designer correct?

No, the designer’s suggestion would be an NEC violation. The NEC requires separately derived systems to be grounded. The installation you described is not a separately derived system, as the generator is grounded through a solid connection to the grounded conductor of the service supplied system. See the definition of “separately derived system.” A generator installed as a standby source for a service-supplied building or structure requires a transfer switch. 

The installation could be used for an emergency system, legally required standby system or an optional standby system. In most commercial installations, 3-pole transfer switches are used, meaning that the grounded conductor (neutral) of the service-supplied system is solidly connected to the neutral of the standby source at the transfer switch. As noted in your question, this system employs a 3-pole transfer switch. No additional grounding electrode, electrode system or grounding electrode conductor is required, nor is it permitted. Bonding a grounding electrode at the generator or the transfer switch to the grounded conductor would be an NEC violation, as you will be connecting the grounded conductor to ground downstream of the main bonding jumper at the service equipment. That will create current flow on the earth and any conductive object between the grounding point and the service equipment. See the requirement in 250.24(B), which clearly prohibits what the designer was asking you to do. This section exists to prevent current flow on raceways, cable assemblies, the earth, etc., which could result in shock and other serious issues. 

This is further affected with a wye-connected secondary at 480/277V. There could be large amounts of current on the grounded conductor and load side; grounding will place a significant amount of that current on other conductive paths, creating potential shock scenarios. If there is upstream ground-fault protection of equipment (GFPE) as required in 215.10 and 230.95, the grounding requested by the designer could affect the capability of the GFPE, likely resulting in activation of the GFPE due to downstream grounding issues. 

Existing home runs

A medical office is moving into an existing commercial building. There will be exam rooms and patient care spaces. I understand the need for healthcare facility wiring in accordance with 517.13, but I would like to know if I can reuse existing MC home runs, as the panelboard is quite a distance from the space being used. Is that permitted?

No, see 517.13, which addresses “branch circuits” supplying patient care spaces. As defined in Article 100, a branch circuit is the circuit conductors between the final overcurrent device protecting the circuit and the outlet(s). New home runs will be required and must be installed in accordance with 517.13.

AFCI required?

We are converting a portion of a detached garage on a residential property into a party room. It will be heated, but there is no kitchen or bathroom, etc. Section 210.12 does include recreation rooms. Is AFCI protection required?

No, AFCI protection is not required. Section 210.12(B) is called “Dwelling Units,” and the building/structure you described is not a dwelling unit. It does not contain complete and independent living facilities for one or more people, including permanent provisions for living, sleeping, cooking and sanitation. If the garage were attached to the dwelling, it would be part of the dwelling unit, and Section 210.12(B), list item (10) would require AFCI protection. It is important to note that 210.8(B) list item (10) applies, as the garage is not part of a dwelling unit and requires all 125V through 250V receptacles, 50A or less, be GFCI protected.

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