Jim Dollard has an extensive background in codes and standards. Send questions about the National Electrical Code (NEC) to Jim at firstname.lastname@example.org. Answers are based on the 2020 NEC.
Time constraints for temporary power
Due to the COVID-19 pandemic prohibition on indoor dining, many restaurants in our township installed temporary power to open-sided tents and outdoor seating areas. At the inspection, we stated that they could not be in place longer than 90 days. We are now well over 90 days and concerned with fallout if an electrical incident occurs. We do not want to tell the business owners to remove the installation. What should we do?
Section 590.3, “Time Constraints,” is separated into four, first-level subdivisions. 590.3(A), “During the Period of Construction,” permits temporary power to remain until the construction-related activities are complete. 590.3(B), “90 Days,” applies only to holiday decorative lighting and similar purposes. 590.3(C), “Emergencies and Tests,” is intended to apply where there is an emergency such as a flood or the loss of service equipment and where tests are performed, such as load testing a standby generator. 590.6(D) requires that temporary wiring be removed upon completion. This type of installation is certainly not construction-related, nor is it similar to holiday decorative lighting. It is my opinion that, when written, the intent of 590.3(C), “Emergencies and Tests,” never considered a pandemic. However, this truly is a different type of emergency and the 90-day limitation would not apply. I agree with your decision to not tell restaurant owners to remove these installations. We all need to recognize that these extraordinary circumstances require a different approach. During construction, temporary wiring is permitted to remain in place for as long as necessary, partly because the installer of the temporary power (electrical contractor) typically remains on-site until completion. I would suggest that you periodically revisit these installations to ensure the temporary power was not damaged or modified until we get through these difficult times.
Splash pad bonding
Does a splash pad in a public park require equipotential bonding of perimeter surfaces?
No. See the definition in 680.2 that clarifies that a splash pad is a fountain that has a depth of 1 inch or less and is intended for recreational use by pedestrians. Part V of Article 680 covers fountains and 680.50 requires that only Part I, “General,” and Part V, “Fountains,” apply to the installation of a splash pad. The requirements for equipotential bonding of perimeter surfaces are located in 680.26, which is in Part II, “Permanently Installed Pools.” There are grounding and bonding requirements for splash pads including, but not limited to, those in 680.54.
Listed transfer equipment
What does the 2020 NEC require for optional standby transfer? I use commercial interlock kits on existing load centers. When applying for a permit, the inspector informed me that I had to have a listed transfer means. The kits that I use state that they are tested for use with UL 64 panelboards. Does that meet Code?
No. The requirements of 702.5 were significantly revised in the 2020 NEC . The general rule in 702.5(A) is that transfer equipment be installed where an electric utility supply is either the normal or standby source. New 702.5(D) “Inadvertent Interconnection,” requires transfer equipment to be suitable for the intended use, and it must be listed, designed and installed so as to prevent the inadvertent interconnection of all sources of supply in any operation of the transfer equipment. The 2017 NEC did not require transfer equipment to be listed. The interlock kit you describe is apparently not a listed product. Simply stating on product literature that the interlock mechanism is tested on a panelboard listed to UL 64 does not mean that the kit is listed. Research listed products for transfer of an optional standby system.
When does 240.87 apply?
Where a circuit breaker is installed with restricted access as permitted in the Code, does 240.87 apply if I adjust the trip unit to 1,000A? The inspector asked if the circuit breaker could be adjusted to 1,200A. The answer is yes, but we adjusted it to 1,000A. The inspector required a means of arc energy reduction be applied. Was that required?
Yes, the inspector is correct, the requirements of 240.87 apply. To answer this question, it is imperative that we fully understand the requirements of 240.6 “Standard Ampere Ratings.” This section provides standard sizes of fuses and inverse time type circuit breakers in Section 240.6(A) and the associated table.
Because this involves an adjustable trip circuit breaker, we need to go further in Article 240 to determine how to rate this device. There are two methods: (1) 240.6(B) requires that the rating of an adjustable trip circuit breaker that has an external means for adjusting the current setting of the longtime pickup, that is not installed with restricted access, must be the maximum setting possible. This means a circuit breaker that can be adjusted to 1,200A with long time pickup adjusted to 1,000A has a 1,200A rating because restricted access was not provided. (2) 240.6(C) provides four methods to achieve restricted access of adjustable trip circuit breakers. If one of those methods, such as (2), locating the adjustable trip circuit breaker behind bolted equipment enclosure doors, is applied, the same 1,200A circuit breaker that is set to 1,000A will have a rating of 1,000A.
This section is in Part I General, and it exists to correlate with other general NEC requirements, including, but not limited to, protecting conductors at their rated ampacity. Section 240.87 is located in Part VII Circuit Breakers. The parent text of 240.87 recognizes the NEC requirements for rating an adjustable trip circuit breaker as seen in 240.6(B) and (C). The parent text states that: “Where the highest continuous current trip setting for which the actual overcurrent device installed in a circuit breaker is rated or can be adjusted is 1,200A or higher, 240.87(A) and (B) shall apply.”
The first part of this requirement recognizes the ratings in 240.6(B) and (C). However, the end of that sentence modifies those general rules by adding “or can be adjusted is 1,200A or higher.”
This section modifies the general rating requirement. To summarize, if you have a 1,200A frame circuit breaker, with the long time setting at 1,000A, installed with restricted access, and the trip unit (the actual overcurrent device installed in a circuit breaker) can be adjusted to 1,200A or higher, 240.87 applies. If that same circuit breaker in the same installation had a trip unit that could not be adjusted to 1,200A or higher, 240.87 would not apply.
When installing cable assemblies in conduit, where do we get the area in square inches to calculate the required size of conduit?
Where cable assemblies are permitted to be installed in a raceway, refer to the XXX.22 section of the raceway article for the permitted number of conductors. These sections send us to Table 1 in Chapter 9. Ten table notes follow Table 1 in Chapter 9. It is important to understand that table notes in the NEC are enforceable; they are not informational. Typically, you go to Table 5 for dimensions of standard insulated conductors, Table 5A for compact conductors and Table 8 for bare conductor dimensions. When dealing with a cable assembly, you may be able to refer to manufacturer specs or simply measure the cable diameter and cross-reference Table 5. For example, if a cable assembly is 0.75 inches in diameter, we can compare it to a 300 kcmil XHHW, which has a diameter of 0.76 in. We can then apply the area in square inches for a 300 kcmil XHHW, which is 0.4536 square inches.
Luminaires as a raceway
We have an installation of end-to-end lighting fixtures that will contain two circuits in each row. The second circuit is intended to illuminate an aisle space and will be left on 24/7. Can we use the lighting fixtures themselves to route the second circuit into the middle of the fixture run?
Yes. Section 410.64 provides a general prohibition of using luminaires as a raceway unless one of three subdivisions apply. Luminaires are permitted to be used as a raceway where they are listed and marked as such and where they are identified for through-wiring, as permitted by 410.21. Section 410.64(C) permits luminaires designed for end-to-end connection in a continuous assembly to contain the conductors of a two-wire branch circuit, or one multiwire branch circuit, supplying the connected luminaires. Where these requirements are met, the luminaire is not required to be listed as a raceway. 410.64(C) also permits one additional two-wire branch circuit to separately supply one or more of the connected luminaires.