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. Send questions to firstname.lastname@example.org. Answers are based on the 2017 NEC.
Accessibility of busway switches
During the design phase of a mid-rise structure, an engineer observed that the electrical rooms with vertical busway with multiple fused switches installed will result in one switch being mounted so high that a hook stick must be included in each closet to operate the switch. We objected and informed the engineer that the bus switches supply panelboards that have main circuit breakers. The engineer is demanding we comply with 404.8. Does this require a chain or hook stick to operate?
No. The engineer is correct in his interpretation of 404.8, but he needs to dig a little deeper. There are several sections in the NEC we must review. First, 240.24 provides requirements for the location of overcurrent protection in the circuit. By definition, the conductors from the fused busway switches to the main circuit breakers in the panelboards are feeders. Section 240.24(A) requires switches to be mounted in a readily accessible location and installed so the center of the operating handle grip is not higher than 6 feet, 7 inches above the floor.
Multiple exceptions are included in positive text. One of those permitted alternate methods in 240.24(A)(1) permits installation in accordance with 368.17(C). Article 368 contains requirements for busway installation. The general rule in 368.17(C) requires that, where these devices are mounted out of reach and contain a disconnecting means, there must be an additional suitable means such as a rope, chain or stick to operate the disconnect from the floor. Exception No. 4 permits an installation without a method of floor operation where the busway plug-in switch—containing overcurrent protection that is not readily accessible—supplies a readily accessible disconnect. In these cases, a floor operation method is not required.
There is a need to provide clarification in 404.8(A) Exception No. 1. This exception addresses busway installations and requires a means to operate plug-in devices from the floor where they are not readily accessible. This must be correlated with the requirement in 368.17(C).
Could you please elaborate on what constitutes the definition of “reconditioned” electrical equipment as far as the 2017 NEC refers to?
The NEC does not define the term “reconditioned.” The informational note following 110.21(A)(2) refers the Code user to industry standards that are available to determine proper application of reconditioned or refurbished equipment. The best resource for such information is the original equipment manufacturer. See the publicly available “NEMA Policy on Reconditioned Electrical Equipment” for detailed information.
NEMA defines reconditioning as the process of restoring electromechanical systems, equipment, apparatus or components to operating condition as recommended by the manufacturer’s instructions, using only design-qualified parts. Reverse-engineered parts (designs copied from existing parts by other manufacturers) are not considered to be design-qualified parts unless specifically design-verified under applicable standards.
Electrical industry practitioners and others may also use the following terms to describe the process of reconditioning: remanufacturing, refurbishing, recycling, repairing, restoring, rebuilding, re-engineering and reusing.
It is imperative to obtain the service records of equipment that is going to be or has been reconditioned. This allows one to determine the environment in which the equipment was originally used. Where and how the equipment was used previously may significantly impact safety. Note that both the NEMA policy and the informational note following 110.21(A)(2) state normal servicing of equipment that remains within a facility does not qualify that equipment as reconditioned or refurbished.
For example, where low-voltage power circuit breakers are maintained by qualified International Electrical Testing Association technicians as required by the manufacturer and NFPA 70B, those devices are not considered reconditioned. They are considered properly maintained equipment. The NEMA policy also contains valuable information that describes equipment that is not suitable for reconditioning. This includes but is not limited to adjustable speed drives, dry-type transformers, fire pump controllers, molded-case circuit breakers, surge protective devices and transfer switches.
When a 480-volt (V) fire pump is installed with service conductor taps as permitted in 230.82, can we apply the rules in 240.21(B)(5) for outside taps? The conductors will be tapped in a wireway in the electrical closet and run in PVC conduit under more than 2 inches of concrete, and they will be considered outside of the building. Additionally, is it required to bring a neutral conductor to fire pump equipment that does not need a neutral? The service is 208/120V, but we need only three-phase, 208 for the fire pump.
There are multiple problems with the installation you describe. Section 230.82 provides a list of equipment that is permitted to be connected on the supply side of the service disconnect means along with prescriptive requirements to ensure a safe installation. List item 230.82(5) permits taps used to supply multiple types of equipment, including fire pump equipment and fire and sprinkler alarms if they are provided with service equipment and installed in accordance with requirements for service-entrance conductors. The taps 230.82(5) refers to are service conductors.
The second section of Article 240, Overcurrent Protection, defines the term “tap conductor.” If this definition were intended to apply in other articles, it would be located in Article 100. As defined, a tap conductor is a conductor, other than a service conductor, that has overcurrent protection ahead of its supply point that exceeds the value permitted for similar conductors protected as 240.4 describes elsewhere. This definition clarifies that it does not apply to service conductors. The conductors described in your question are service conductors, not tap conductors.
In addition, where a feeder is tapped and the provisions of 240.21(B)(5) are applied, the tap’s supply point must be located outside of the building. It is not permitted to tap a feeder inside of a building or structure, install the tap conductors under 2 inches of concrete, and consider them outside of the building. Section 230.6 applies only to service conductors. The permissive requirements of 230.82(5) require the service conductor taps to be installed in accordance with requirements for service-entrance conductors. The disconnect in the fire pump equipment will be a service disconnect and must be rated as service equipment. A grounded conductor must be installed and taken to the (service equipment) fire pump controller in all cases where service conductors supplying the equipment are from a grounded AC system operating at 50–1,000V in accordance with Section 250.20(B).
Multiwire branch circuits
The NEC does not allow lighting and power loads that are supplied by an emergency system to be on a multiwire branch circuit. Is it permissible to supply only lighting from a multiwire branch circuit?
No. The requirement you reference is Section 700.19, Multiwire Branch Circuits. The text in this section is directed at and applies to each “emergency system branch circuit.” The reference to “emergency lighting and power circuits” simply includes all lighting and power loads. It does not imply a combination of lighting and power loads. Emergency system branch circuits are not permitted to be supplied from a multiwire branch circuit. The load served does not impact the requirement. This rule’s intent is to limit the loss of emergency supplied equipment if an overcurrent occurs.
For example, consider a three-pole circuit breaker supplying a multiwire branch circuit with three 277V circuits for emergency lighting from a 480/277V system in a commercial occupancy. If an emergency causes one of those circuit breakers to open, all three circuits would be lost. This requirement ensures that, in this type of situation, only the affected circuit would be lost during an emergency.
Fire alarm wiring and 300.4
Is it permitted to install fire alarm wiring, boxes and devices directly to roof decking? I am in an existing structure and can see the deck screws coming through the roof with wiring and devices right next to them. I see that as a major problem when the roof gets replaced!
Yes. The requirement to protect cables, raceways and boxes installed in or under roof decking is found in 300.4(E). However, Section 760.3 mandates that only those sections of Article 300 referenced within Article 760 apply to fire alarm systems. Throughout Article 760, there are multiple references to requirements in Article 300. The only reference to Section 300.4 is found in 760.24(A), which references 300.4(D) for general protection requirements from nails or screws where fire alarm cable is installed in framing members. There is no reference to 300.4(E) in Article 760.
I share your concern of potential damage to the fire alarm system when the roof is replaced. When the roof does get replaced, there is a significant probability that damage will occur. If a decking screw penetrates a fire alarm cable or device, it will not create a shock hazard, but it will compromise the fire alarm system. This is further complicated if qualified people are not maintaining the fire alarm system and the trouble indication gets silenced. It is interesting that both the requirements in 300.4(E) and Article 760 are under the purview of the same committee.