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 2020 NEC.

Circus tent wiring—portable or temporary?

A local community event included a traveling show that was essentially one large circus tent. A single generator supplied power primarily for lighting and show-related loads. There were cables and cords laid on the ground, but Article 590 prohibits that. The township inspected the installation and asked us if this was temporary wiring or an Article 525 installation. How does one make that determination?

As described in your question, this installation would fall under the scope of Article 525. Requirements of this article include the installation of portable wiring and equipment for carnivals, circuses, fairs and similar functions, including wiring in or on all structures. The key here is that Article 525 installations are considered portable wiring, not temporary wiring. These installations are typically installed for a short period of time, broken down, relocated and set up again in the same manner in another location.

Temporary wiring installations are typically installed for longer periods of time and are not designed to be installed over and over again in different locations in the same manner. With respect to the cords and cables you noted, they are permitted to be on the ground. In this case, the distribution of feeders and branch circuits falls under the scope of Article 525, not Article 590.

Permitted wiring methods are addressed in Part III of Article 525. The general rule for flexible cords and cables requires them to be listed for extra-hard usage. However, where they are not subject to physical damage, they can be listed for hard usage only. These venues are almost exclusively installed outdoors, and all flexible cords and cables must also be sunlight-resistant and listed for wet locations. Single-conductor cables are permitted, but only in sizes 2 AWG or larger. Where these permitted cords and cables are installed in areas that are accessible to the public, they must be installed to minimize potential tripping hazards. It is permitted to cover these cables with nonconductive matting secured to the ground or to protect them in another approved manner. The key here is that the method of protection is not permitted to create a greater tripping hazard than the uncovered cables.

Small appliance branch circuits

Where the countertops in a dwelling unit kitchen are separated into multiple sections, are two small-appliance branch circuits (SABCs) required for each section? We had townhouses where the design included a small section of countertop in each unit. The space was about 18 inches, and we installed a single duplex receptacle that was GFCI-protected and supplied from one of the SABCs. The electrical inspector demanded that we add another receptacle to the space supplied from a different SABC or split the top and bottom of the device with two circuits. Is that right?

No, the inspector in this case was incorrect, and the interpretation went beyond minimum NEC requirements. To provide the necessary clarity, we must look at all of the related requirements. Section 210.11(C)(1) requires a minimum of two 20A SABCs for all receptacle outlets specified by 210.52(B), which addresses receptacle requirements for small appliances. It requires that the two SABCs supply all wall and floor receptacle outlets covered by 210.52(A), all countertop outlets covered by 210.52(C) and receptacle outlets for refrigeration equipment. Kitchen receptacle requirements are addressed in 210.52(B)(3).

This section mandates only that the receptacles installed in a kitchen to serve countertop surfaces be supplied by not fewer than two SABCs. It very clearly states “countertop surfaces,” not “each separate countertop space.” The use of the plural “surfaces” is intentional. This requirement does not provide any prescriptive design-related requirements. If the intent of the NEC was to require each separate countertop space be supplied by two SABCs, it would say just that. See Section 90.1(A); the NEC is not intended as a design specification.

The reason the NEC requires that both required SABCs serve the countertop is due to typical use. Multiple small appliances, such as a coffee maker or toaster, will be located on the countertop.

It’s important to note that there is no limit to the number of SABCs installed in a kitchen. While the minimum is two SABCs, a homeowner may request that each countertop receptacle outlet be supplied from an individual SABC. The NEC does not require that a single countertop space be supplied with two SABCs. The requirement is that the combined countertop surfaces be supplied with not less than two SABCs.

NFPA 70 (NEC) and NFPA 70E

Why do we have separate documents for electrical installation and electrical safety? The NEC users are the very same people that need to use NFPA 70E to work safely. Wouldn’t it just make sense to combine them? That way NFPA 70E would become mandatory when a state adopts the NEC.

NFPA 70, the NEC , and NFPA 70E, the Standard for Electrical Safety in the Workplace, share the same goal: safety. However, they are dynamically different. The NEC is limited to installation requirements only. NFPA 70E includes safe work practices and much more, but it does not contain any installation requirements.

It is also extremely important to note that while people installing and maintaining electrical systems need safe work practices, so do people in many other occupations. NFPA 70E addresses all workplaces, not just electrical construction. With respect to application of NFPA 70E, electrical construction, renovation and maintenance are all activities covered by OSHA regulations. OSHA requires that employers provide safe working conditions for their employees. OSHA regulations drive compliance with NFPA 70E—OSHA is the “shall,” and NFPA 70E shows us how.

2,000A service conductors for overload protection

We submitted a change order to install aluminum service conductors instead of copper due to cost. The GC’s engineer replied that the conductors were too small and were in violation of Section 230.90. This installation has six service disconnects (circuit breakers) in separate enclosures, four 200A, one 400A and one 800A. This engineer wants conductors sized at 2,000A for overload protection. The design drawings had four parallel 600-kcmil copper, which after derating gets to 1,520A. We offered an equivalent in aluminum. Do we need 2,000A of conductor?

No. The general rule in Section 230.90 is that each ungrounded service conductor be protected from overload, which means a single OCPD cannot exceed the ampacity of the service conductors. See Exception No. 3 to 230.90 that permits the six disconnects in your question to serve as the overcurrent device to providing overload protection. This exception permits the sum of the ratings of the six circuit breakers you described to exceed the ampacity of the service conductors. This exception can be applied where the calculated load does not exceed the ampacity of the service conductors.

Cable tray in industrial-to-residential renovation

An old factory is being renovated into apartments. There are four runs of 4-inch EMT for feeders that need to get into the switchboard. The existing space is not very high, and we cannot get 4-inch 90s into the top of the switchboard. Instead of a custom-built junction, can we just use cable tray for the conductors from where the conduits enter the room and cut an opening in the top of the switchboard?

No. Individual conductors in cable tray are only permitted in industrial establishments. See Section 392.10(B). The NEC does not define “industrial;” the scope of Article 100 clarifies that the NEC does not try to describe commonly defined general terms. Industry is commonly defined as economic activity concerned with the processing of raw materials and manufacture of goods in factories. The venue described in your question is not industrial; it is an apartment house. I suggest that you check the zoning for the property in question.