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.
Swimming pool feeder
We installed type SER aluminum cable indoors from an attached garage to supply a new panelboard in a home’s basement. The panelboard was added to resupply a couple of circuits to an outdoor pool shed and circuits for a new woodworking shop. The circuits to the pool are in PVC conduit with all insulated copper conductors. The inspector wants us to rip out the feeder and use something with an insulated copper grounding conductor. Is he right?
No, the feeder you installed is in a dry location that is not a corrosive environment. Over the last few NEC revision cycles, requirements for insulated copper equipment grounding conductors (EGC) for swimming pools have been revised and provide significant clarity. The intent of requirements in Article 680 for insulated copper EGCs is to ensure an effective ground fault path where a corrosive environment may exist.
Section 680.7 provides grounding and bonding requirements for swimming pool installations. 680.7(A) requires feeders and branch circuits installed in a “corrosive environment or wet location” to contain an EGC in an insulated copper conductor sized in accordance with Table 250.122, but not smaller than 12 AWG. All conductors installed outdoors or underground are in a wet location. A corrosive environment is defined as an area or enclosure without adequate ventilation, where electrical equipment is located and pool sanitation chemicals are stored, handled or dispensed.
The requirements in 700.10(D)(2) are there to protect feeders from fire. Permitted methods include installation in a listed fire-rated assembly that has a minimum fire rating of 2 hours containing only emergency circuits, or encasement in 2 inches of concrete. All that said, instead of installation in concrete, can service conductors be run to the fifth floor in a midrise building if they are installed in a drywall assembly that is 2-hour rated with just service conductors?
No, those requirements in Article 700 are only for fire protection. Feeder conductors are required to be protected at their rated ampacity. Should physical damage occur to an emergency feeder, there is an upstream overcurrent protective device that will open. Service conductors are unprotected and require physical protection from damage where they are run inside of a building or structure. See Section 230.6 that provides prescriptive conditions under which service conductors are permitted to be run inside of a building. Based on your question, it is assumed that for some reason, the building design requires the service equipment to be installed on the fifth floor. There is one condition referenced in 230.6 (list item 2) that you can apply to provide the required physical protection. Raceways containing the service conductors could be encased in concrete or brick not less than 2 inches thick.
Can I use the volume in cubic inches marked on plastic device boxes instead of the values provided in Article 314? Trying to save costs.
Yes, Table 314.16(A) provides volume in cubic inches for standard size boxes not marked with their volume by the manufacturer; see 314.16(A)(1). Nonmetallic boxes are required by 314.16(A)(2) to be marked with their volume by the manufacturer in a durable manner. Where a box is marked with a volume larger than the values in Table 314.16(A), the larger volume is permitted. It is important to note that the NEC values in cubic inches for box fill are the minimum permitted. Larger boxes will allow for easier installation. When applying box fill as tight as you can get it with splices and devices, the installation can become a challenge. When working with the minimum space permitted, to neatly get everything back into the box and get the cover on, installers in many cases must be part magician and part electrician.
517.13 and luminaires
Are overhead lighting fixtures in a lay-in type ceiling required to have hospital grade MC cable in healthcare spaces? How about the switches?
The requirement you are referencing is in 517.13 and addresses EGCs for receptacles and fixed electrical equipment in patient care spaces. Luminaires are fixed electrical equipment. “Patient care space” is defined as any space of a healthcare facility wherein patients are examined or treated. This section requires an effective ground-fault current path by installation in a metal raceway system or a cable having a metallic armor or sheath assembly in addition to an insulated copper EGC clearly identified along its length by green insulation within the wiring method. The exception following the parent text of 517.13 allows luminaires more than 7½ feet above the floor and switches located outside of the patient care vicinity to be installed with standard wiring methods (no redundant ground fault path). The patient care vicinity is within a location intended for examining and treating patients that extends 6 feet beyond the normal location of the bed, chair, table, treadmill or other device that supports the patient and extends vertically to 7½ feet above the floor.
Set screws and RMC fittings
Where there is a need to cut rigid metal conduit (RMC) in an outdoor installation, are standard set screw couplings permitted?
No, a listed compression type fitting is required. See 344.42(A) for requirements when using threadless fittings. This section requires that RMC fittings used in a wet location comply with 314.15, which mandates fittings listed for use in wet locations.
Industrial control panel marking
Can the labeling for industrial control panels be located inside the enclosure? We typically place the labeling inside when the control panel is located outdoors. An engineer is claiming that is a Code violation. Is that true?
Marking requirements for industrial control panels are located in Section 409.110. There are seven list items detailing information required to be marked either on or inside the enclosure. The information in list items (2) and (3) are required to be attached to the outside of the enclosure. The supply voltage, number of phases, frequency and full-load current for each incoming supply circuit must be marked on the outside of the enclosure.
Additionally, if the industrial control panel is supplied by more than one electrical source and more than one disconnecting means is required to disconnect all circuits 50V or more within the control panel, it must be marked on the outside to indicate that more than one disconnecting means is required to de-energize the equipment. Where this occurs, the location of each disconnecting means necessary to disconnect all circuits 50V or more must be documented and available. One method is to attach it on the outside of the enclosure with the information noted above.
Type NM in commercial space
Can Romex (Type NM cable) be used in a commercial space (Type 3 building) above a lay-in type (2 x 2 tiles) ceiling? After all, once the cable is installed and the ceiling tiles are in, it is not exposed, right?
No, see Section 334.12 for uses not permitted where Type NM cable is installed. List item (2) in 334.12(A) prohibits Type NM from being installed where it is exposed within a dropped or suspended ceiling cavity in other than one- and two-family and multifamily dwellings. The definition of “exposed” when applied to a cable assembly such as Type NM cable is “on or attached to the surface or behind panels designed to allow access.” The 2 x 2 tiles are designed to be removed, allowing access to the ceiling space above and the Type NM cable.
stock.adobe.com / alex83m
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].