Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Questions can be sent to email@example.com. Answers are based on the 2014 NEC.
Panelboards in cabinets?
I am working in a commercial occupancy on new equipment that contains panelboards that are not installed in a cabinet or cutout box. The definition of a panelboard requires that it be in a cabinet. This equipment contains panelboards that are open in the back, as well as transformers. Is this permitted?
Yes. Definitions in Article 100 are not permitted to contain requirements. As you have pointed out, panelboards are typically installed in cabinets. The definition clearly permits panelboards to be installed in cabinets or cutout boxes; placed in or against a wall, partition or other support; and accessible only from the front. Section 408.38 requires panelboards to be mounted in cabinets, cutout boxes or identified enclosures, so this section permits the equipment you describe. Panelboards are also required, in all cases, to be dead-front.
Resetting the instantaneous trip
We have been made aware of a new NEC requirement to provide a means of arc-energy reduction for circuit breakers rated at 1,200 amperes (A) or higher. We are in the design stage on a new project and are considering the options to be in compliance. In the permitted methods to reduce clearing time, list item five permits an approved equivalent means. What is an approved equivalent means? We have been told that there is no need to provide zone-selective interlocking or an energy-reduction maintenance switch because a worker can simply change the circuit-breaker instantaneous setting during the period of time work is being performed and then return it to the original setting. While that seems like a more cost-effective option, it is a cause for concern because we are the designing engineers. It is our opinion that only qualified people should perform such modifications. Would allowing a worker to just change the circuit-breaker instantaneous setting be an approved equivalent means of arc-energy reduction?
No, in fact, allowing a worker to manually adjust any circuit-breaker setting creates very serious issues.
The requirement for arc-energy reduction (located in Section 240.87) applies where the highest continuous current trip setting for which the actual overcurrent device installed in a circuit breaker is rated or can be adjusted to 1,200 amperes or higher. The permitted methods to achieve arc-energy reduction in the 2014 NEC include the following:
- Zone-selective interlocking
- Differential relaying
- An energy-reducing maintenance switch with local status indicator
- An energy-reducing active arc-flash mitigation system
- An approved equivalent means
Adjusting a circuit breaker’s instantaneous setting as a means of arc-energy reduction would not qualify as an “approved equivalent means.”
Section 90.4 permits an authority having jurisdiction by special permission (written consent) to “permit alternative methods where it is assured that equivalent objectives can be achieved by establishing and maintaining effective safety.” Adjusting the instantaneous trip setting each time a means of arc-energy reduction is activated would be prohibited because it cannot achieve equivalent objectives to maintain the safety-driven requirements of Section 240.87 and would potentially create serious problems including but not limited to the following:
- No local status indicator is provided. The local status indicator as found in Option 3 of Section 240.87 for an energy-reducing maintenance switch is important to ensure the user knows the incident-energy reduction method is engaged. This is also important from an awareness perspective to ensure settings are returned to normal when the work is complete.
- The worker may adjust the wrong setting, creating issues with long time pickup/delay, short time pickup/delay and serious safety concerns due to a lack of arc-energy reduction. If the wrong setting is adjusted, the clearing times are not affected. The worker will not know if they are reducing or increasing clearing time.
- Rotating dials on the face of the breaker does not provide indication to the worker as to what the original setting was after being changed. When resetting the instantaneous trip, the worker may not be capable of achieving the setting required by the original coordination study. This may result in potential damage to downstream devices, conductors and equipment. Allowing a worker to make any temporary adjustment to an overcurrent protection device setting may create serious and permanent problems for all NFPA 70E labeling at that location and downstream.
Section 240.87(B)(3) already recognizes eduction of circuit breaker clearing time to achieve arc-energy reduction by altering the instantaneous setting on the circuit breaker for an energy-reducing maintenance switching with local status indicator. Note that this switch is an identified accessory that, when turned on, reduces clearing time and, when turned off, automatically restores the preset coordination to the exact same setting. The worker doesn’t have to do guess work.
In addition, a “local status indicator” is required. This is essential to ensure the energy-reducing maintenance switch is turned off after the work is performed, which returns the circuit breaker to the exact same instantaneous setting required by the original coordination study.
Allowing a worker to adjust the instantaneous trip setting on a circuit breaker is just asking for problems.
Where an engineer or contractor designs a system that requires a worker to adjust the instantaneous setting of a circuit breaker to comply with Section 240.87’s requirements, they are in violation of the NEC and subject to significant liability. The 2017 NEC will provide additional clarity for the permitted methods of arc-energy reduction by recognizing two new methods to reduce arc energy:
- An instantaneous trip setting that is less than the available arcing current
- An instantaneous override that is less than the available arcing current
Note that no permitted methods in the 2014 or the 2017 NEC allow a worker to “adjust” any instantaneous settings.
Supporting cables and boxes in suspended ceiling
In suspended ceilings, we support both boxes and MC cable by adding 9 AWG wire to the wires that support the suspended ceiling. It is our understanding that only these additional wires may be used for supporting cables and boxes. Another contractor on the job disputes our position and uses the ceiling support wires, claiming the ceiling manufacturer permits it. The contractor cannot prove it but says that Article 314 allows boxes to be supported in that manner. Is this new?
No, both the general requirements in Section 300.11 and the support requirements for boxes in Section 314.23(D) require an “independent means of secure support.” The requirements in Article 314 mirror Article 300. Second-level subdivision 300.23(D)(2) mandates support of junction boxes in suspended ceilings to be performed in accordance with Section 300.11(A), which requires “independent means of secure support.” Section 300.11 permits connection of additional support wires to the ceiling assembly to achieve secure support. Section 314.23(D)(2) provides more clarity by mandating the additional support wires used for enclosure support to be fastened at each end so as to be taut within the ceiling cavity.
Optional standby signs
Where a generator is installed in a dwelling unit for optional standby, we are required to install a sign at the service equipment in case of power loss. Different inspectors want different types of signs. What type of sign is required and does this rule even exist?
The requirement in Section 702.7(A) lacks clarity on the specific type of sign. In my opinion, the requirement is for a sign, so that means it is something that is placed on the equipment. It could be a as simple as a label applied that is handwritten. I suggest you submit a public input for the 2020 NEC that clarifies the requirement with respect to the type of sign and its capability of withstanding the environment.
The requirement should also require that it not be handwritten. These signs are essential for safety. Another installer/maintainer needs to know if there is an optional standby system and where it is located. First responders need this information as well; they need to know that opening the service disconnect may not completely remove power within the structure.
Electrically powered pool lifts
What are the requirements for pool lifts that are used to help the disabled get into and out of pools? I have seen these at hotels but never installed one. Are they wired at 120 volts?
The 2014 NEC does not contain specific requirements for electrically powered pool lifts. A new Part VIII in 2017 NEC’s Article 680 covers this type of equipment. Pool lifts may be connected to premises wiring or may be battery operated.
The new requirements will define “electrically powered pool lifts” in Section 680.2 and mandate them to be listed with nameplates containing prescriptive information. Three exceptions allow for unlisted pool lifts provided the referenced requirements for battery charging and voltage levels that do not exceed the low-voltage contact limit are met. A pool lift connected to premises wiring and operated above the low-voltage contact limit will require ground-fault circuit interrupter protection for personnel. All pool lifts will be required to be bonded in accordance with 680.26(B)(5) and (B)(7). It is important to note that bonding and other requirements in the 2014 NEC apply as well for electrically powered pool lifts.