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.

Counterfeit electrical equipment

In a new commercial building, we are installing new branch circuits and utilization equipment. We did not do the core and shell. Our foreman noted something weird and asked if circuit breakers with a marked temperature limitation of only 70°C can be used at 75°C. If not, we need to size all the branch circuits according to their 60°C ampacity. Can you help?

Over the course of my career, I have seen circuit breakers rated at 60°C only and at 60/75°C (since most are dual-rated), but never at 70°C. I did some research and contacted an engineer with a very strong background in overcurrent protective devices (OCPDs) that worked for the manufacturer you noted. We could not locate any devices like the circuit breakers you referenced and photographed only rated at 70°C.

It is possible and, in my opinion, likely, that they are counterfeit devices. There is a significant problem nationwide with respect to counterfeit electrical equipment. When buying electrical equipment, contractors should always purchase through a supply house or other retail entity that has a direct relationship with the electrical equipment manufacturer. The use of counterfeit circuit breakers may lead to overheating, short circuits, fires or worse. 

Individual circuits for EV chargers

In a parking garage, we installed a 200A feeder to supply three EV chargers, which are each rated at 48A full-load current. We installed junction boxes in the feeder run and used the 10-foot tap rule to supply 60A circuit breaker enclosures that supply each EV charger. Is that permitted? An engineer said we need individual circuits.

The NEC refers to EV chargers as Electric Vehicle Supply Equipment.

The general rule in Section 625.40 requires that each EV charger greater than 16A or 120V be supplied by an individual branch circuit. The load side of each circuit breaker you installed is where the branch circuit begins, so you have met the requirement for individual branch circuits.

Section 625.41 requires the overcurrent protection for feeders and branch circuits supplying EV chargers be sized for continuous duty and have a current rating of not less than 125% of the maximum load of the equipment. The maximum load is 48A. Doing the math: 48 x 1.25 = 60A, so the circuit breakers installed are correctly sized. For the feeder: 3 x 60 = 180 and the 200A feeder is properly sized. It should be noted that there are permissive requirements allowing multiple EV chargers to be supplied by a single branch circuit. This is limited to the permissive requirements in 625.42(A) for energy management systems and 625.42(B) where the EV charger has adjustable settings and restricted access.

Discharging capacitors at 480V

Does the NEC require capacitors at 480V to be discharged for safety?

Yes, see Section 460.6, which requires a means of discharging stored energy be provided. After disconnection, the voltage must be reduced to 50V or less within one minute. The discharge circuit can be permanently connected or provided with automatic means of connecting it to the terminals of the capacitor bank upon removal of voltage from the line. Manual means of switching/connecting the discharge circuit is not permitted. The NEC is an installation document only; for safety-related work practice requirements involving capacitors, see 2024 NFPA 70E Article 360 and Informative Annex R.

SPDs mounted inside a panelboard

There is a debate over how a surge protective device (SPD) can be installed in a recessed panelboard in a home. When possible, on panelboards that are not recessed, we use a knockout and locknuts to mount the SPD externally. Is it permitted to use the same type of SPD and just lay it inside of a recessed panelboard?

No, SPDs are required by 242.6 to be a listed device, and 242.9 requires that all SPDs provide an indication they are functioning properly (typically a green light). Section 110.3(B) requires all listed equipment be installed and used in accordance with any instructions included in the listing and labeling. The type of SPD you are referencing must be installed externally with the indicator light visible as per the manufacturer’s instructions. Where a panelboard is recessed, manufacturers make SPDs that can be inserted into the panelboard, such as a 2-pole circuit breaker with the indicator light visible.

Buck-boost transformers

Is it permissible to use an autotransformer to step 240V single-phase down to 208V single-phase to supply woodworking equipment? No neutral connection is involved.

The transformer you are referring to is typically known as a buck-boost. The general rule for branch circuits derived from an autotransformer requires the circuit supplied by the autotransformer to have a grounded conductor (neutral) that is electrically connected to a grounded conductor (neutral) of the system supplying the autotransformer. See 210.9. However, Exception No. 1 following this section permits a connection without a grounded conductor where/when transforming from a nominal 208V to a nominal 240V supply or, similarly, from 240V to 208V.

200A transfer switch supplying a 100A panelboard

Can a 200A molded-case circuit breaker in a 200A service-rated transfer switch supply a 100A panelboard that was previously service-supplied?

Yes, based upon the equipment’s physical layout, there are multiple options. See the rules for feeder tap conductors in 240.21(B). The section’s last sentence clarifies that a feeder tap is permitted at any point on the load side of the feeder OCPD. If the transfer switch is located close to the existing panelboard (allowing the 10-foot tap rule in 240.21(B)(1) or 25-foot tap rule in 240.21(B)(2)), conductors rated at 100A can be installed from the load side of the 200A device to a 100A circuit breaker supplying the panelboard. The conductors will have more than one-third the ampacity of the feeder OCPD, must be installed in a raceway and must terminate in an OCPD that limits the load to the tap conductor ampacity.

If the panelboard is located more than 25 feet away, a 200A feeder can be installed to supply the 100A panelboard. If the conductors are too large to terminate in the 100A circuit breaker, the 10-foot tap rule can be applied at the 100A panelboard. In both cases, a full-size equipment grounding conductor based on the size of the feeder OCPD must be installed in accordance with 250.122(G).

Sunlight-resistant SJOOW cord

On an industrial site, drawings require SJOOW cord in limited quantity outdoors. Notes state that the cord must be sunlight-resistant and now, after the installation, we are asked to provide documentation to that end. What do we do?

See Table 400.4, which lists permitted flexible cords and cables. There is a superscript number (9) following Type SJOOW⁹ cord in the table. This refers the Code user to the table notes, which are enforceable. Note 9 to Table 400.4 states that cords with the “W” suffix are suitable for use in wet locations and are sunlight resistant.

RMC without sealing fittings

Rigid metal conduit (RMC) runs were inadvertently run through the corner of a Class 1, Division 1 area and brought to our attention. There are no junction boxes or other equipment, just RMC and couplings made up tight. Do we need to install sealing fittings?

Yes, the couplings are the issue. See the requirement for conduit seals where a conduit leaves a Class 1, Division 1 location in 501.15(A)(4). 

Exception No. 1 following the general rule in this section does permit metal conduit containing no unions, couplings, boxes or fittings to pass through the Class 1, Division 1 boundary. In the situation you described, there are couplings in the RMC run inside the boundary, and conduit seals would be required.

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