Maintenance Requirements, Corrosive Environments and More

By Jim Dollard | Feb 15, 2024

An 800A feeder from the load side of an automatic transfer switch (ATS) supplying emergency loads needed to be rerouted due to renovation in a midrise building.

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.

NEC maintenance requirements

An 800A feeder from the load side of an automatic transfer switch (ATS) supplying emergency loads needed to be rerouted due to renovation in a midrise building. While we did not have to go into the transfer switch, a junction box was added downstream, and I noticed the ATS is severely damaged by exposure to a water leak that has since been repaired. Is maintenance required on that switch? Am I responsible?

Yes, maintenance is required. See Section 700.3(C), which requires all equipment that is part of an emergency system to be maintained in accordance with manufacturer instructions and industry standards. While this requirement is easy to understand and apply, the million-dollar question is not who is responsible for the maintenance (that is the equipment owner), but who is going to enforce it.

In the installation described in your question, the authority having jurisdiction will typically have purview only over the permitted work. I would suggest that you contact the owner through email and inform them that Section 700.3(C) requires all equipment that is part of their emergency system be maintained in accordance with the manufacturer instructions and industry standards. This includes much more than an ATS; other equipment such as standby generators and switchboards or switchgear would also be included.

Additionally, Section 110.17 mandates that electrical preventive maintenance be performed only by qualified persons trained in servicing and maintenance of such equipment. This section also provides prescriptive requirements on materials used in the maintenance process. See Informational Note No. 2 following 110.17 that clearly identifies the applicable industry standard for electrical equipment maintenance, NFPA 70B. While this note identifies NFPA 70B as a recommended practice, that has changed. NFPA 70B is now a standard with mandatory requirements. The problem here is enforcement of equipment maintenance. Most municipalities do not have regulations, laws or staff to enforce maintenance of emergency systems.

Corrosive environments

In a pool house for the pool pumps and equipment for multiple large outdoor pools, is metal conduit permitted?

To answer your question, it is assumed that the pool house is also used to dispense, store or handle pool chemicals such as chlorine. The presence of pool chemicals renders the pool house, by definition in Article 100, a corrosive environment. Section 680.14(A) provides a list of wiring methods considered suitable for use in a corrosive environment, including RMC, IMC, PVC, reinforced thermosetting resin conduit and liquidtight flexible nonmetallic conduit. 

It is important to note that 680.14(B) provides requirements for other equipment including, but not limited to, a panelboard, timers and other control equipment. All other equipment in the pool house must be suitable for use in a corrosive environment, meaning the instructions, listing or labeling must identify it as suitable. If other equipment is not suitable for a corrosive environment, it must be installed in identified corrosion-resistant enclosures. All equipment listed for pool and spa use is considered suitable for a corrosive environment.

SPD requirements

As engineer of record on a project to replace over 100 antiquated load centers in an existing dormitory, I received a request for information questioning why I did not specify surge protective devices (SPDs) as required by the National Electrical Code. Each feeder supplies between 10 and 15 load centers installed in living spaces with feeder taps. Is this a new rule?

New Section 215.18(A) now requires an SPD for feeders supplying dwelling units, dormitory units, guest rooms/suites in hotels and motels, and in areas of nursing homes and limited care facilities used exclusively as patient sleeping rooms. The installation you described supplies dormitory units and will require an SPD in or at each load center. See 215.18(B), which requires the SPD to be installed in or adjacent to distribution equipment connected to the load side of the feeder that contains branch circuit overcurrent protective devices. Additionally, there is an informational note that explains the most effective method of installing surge protection, which is to locate the SPD as close to the source of the branch circuit as possible. While 215.18(A) applies to new feeders, in this case you are replacing the equipment supplied by the feeder and 215.18(D) addresses replacements. The SPD installed in each load center must have a nominal discharge current rating of not less than 10 kA as required by 215.18(E).

Delta high leg red or orange?

A local utility requires that the high leg in a 240/120V, three-phase, 4-wire delta system be identified by the color red and must be on the bottom of the CT cabinet, which is C-phase. This is in violation of NEC rules, right?

The CT cabinet is typically the service point, which is the point of connection between the facilities of the serving utility and premises wiring. The utility company has purview over the CT cabinet installation. Downstream of the CT cabinet all NEC rules apply. Section 110.15 requires marking the high leg in the service equipment (as does 230.56), and at each point on the system where a high leg connection is made if the grounded conductor is also present. The high leg must be identified by an orange outer finish, typically tape. Note that this section does permit the high leg to be identified by marking it orange or “by other effective means.” For example, an installer could decide to use purple as the identifier. For that to be considered as an equally “effective means,” the service equipment and each piece of downstream equipment would need labeling to inform installer/maintainers that the high leg is identified by purple.

Section 408.3(E)(1) requires that switchboards, switchgear and panelboards supplied by three-phase, 4-wire delta systems have the high leg connected to B-phase. The marking requirements of 408.3(F)(1) mandate that each switchboard, switchgear or panelboard supplied by a three-phase, 4-wire delta system be field marked in a legible manner to identify the voltage to ground on the high leg. For example, in the 240/120V, three-phase, 4-wire system described in your question, the labeling would read as “CAUTION B PHASE HAS 208 VOLTS TO GROUND.”

Is parallel EGC permitted?

Is the equipment grounding conductor (EGC) in a cable permitted to be in parallel? There are three current-carrying conductors (black, red and white) in the cable we are using and three green EGCs. Is that permitted?

The EGCs are not in parallel; they are part of a multiconductor cable and are “sectioned.” This is typically done to allow the cable manufacturer to make a very round product so it works well with watertight or waterproof connectors. See Section 250.122(A), which permits EGCs to be sectioned within a multiconductor cable, provided the combined circular mill area of the sectioned EGC complies with the minimum size EGC required in Table 250.122.

Outside branch circuit disconnect

Where a storage shed installed 30 feet from a building is supplied with a single branch circuit (120V), does the required disconnect in the shed need to be service rated?

No, see Section 225.36 for types of disconnects permitted. A snap switch is permitted. Note that a grounding electrode system is not required for a structure (the shed in this case) supplied by a single branch circuit including a multiwire branch circuit; see 250.32(A) exception. The general rule in 225.30 does not permit more than one outside branch circuit to supply a building or structure—a feeder would be required. In that case, 250.32(A) requires a grounding electrode system to be installed. / Christine Bird

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].






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