It’s time to finish going over the changes and additions to Chapter 4 in the 2023 National Electrical Code, and see what’s new in Chapter 5.
430.83(F) Ratings. This new section was added to prohibit the installation of a motor controller if the available fault current exceeds the motor’s short-circuit current rating.
440.8 Single Machine and Location. Section 440.8 was revised to address the increased installation of mini-split air-conditioning systems, which are an alternative to central air conditioning. They are often installed in existing construction where the heating system does not use ducts, such as where electric or hydronic heating systems that use forced hot water are installed. Mini-split systems usually have a single outdoor condenser unit but will have evaporator units in each room to be air conditioned.
Section 440.8 now prohibits the installation of evaporator units in bathrooms in the zone measured 3 feet horizontally and 8 feet vertically from the top of a bathtub rim or shower threshold. This includes the space directly over the tub or shower stall. Most bathrooms are fairly small, which can make it difficult to locate a zone where the equipment can be installed.
440.22(A) Rating or Setting for Individual Motor-Compressor. This section was revised by splitting the last sentence and creating two new exceptions. The existing exception became Exception No. 3. The first addresses installations where the determined value of branch-circuit, short-circuit and ground-fault protection does not correspond with the standard sizes of overcurrent protective devices (OCPDs). The second exception permits the value of an OCPD to be increased in size to as much as 225% if the motor will not start.
445.6 Listing. All stationary generators are now required to be listed. Previously, this requirement only applied to stationary generators rated 600V or less. UL 2200, Standard for Stationary Engine Generator Assemblies, now includes medium-voltage generators.
445.11 Marking. Generator marking requirements were clarified. This criterion is needed to ascertain the performance characteristics of the generator and to specify the OCPD settings. A new requirement was added that prohibits mounting equipment on the generator assembly that conceals or obscures the generator nameplate.
445.18 and 445.19 Disconnecting Means. Section 445.18 was divided into two sections, 445.18 and 445.19. Section 445.18 addresses disconnecting means, and new Section 445.19 addresses emergency shutdown of the prime mover. Section 445.18(B) was also revised to clarify the need for the ability to isolate the generator output terminals from the paralleling system bus. A labeling requirement was added to identify the generator emergency shutdown.
450.43(C) Accessibility. Section 450.43 provides requirements for doors used for transformer vaults. The title of 450.43(C) was changed from “Locks” to “Accessibility” because the content of this section addresses more than locks. It also addresses the direction of egress from the transformer vault. This section was expanded to require that personnel doors be capable of opening at least 90 degrees.
460.24(A) Load Current. Section 460.24(A) provides requirements for switches used to switch capacitive loads on circuits rated over 1,000V, nominal. The requirement was clarified to require switches for capacitive loads be specifically evaluated for a capacitive load. Switch operation must open all ungrounded conductors. Switching devices are often evaluated for switching inductive loads, but not for switching capacitive loads.
Article 480 Stationary Standby Batteries. The title of Article 480 has been changed from “Storage Batteries” to “Stationary Standby Batteries.” The scope was revised to limit it to stationary batteries exceeding one kilowatt-hour. These changes were made to differentiate the batteries covered by this article from those covered by Article 706.
Article 495 Equipment Over 1,000 Volts AC, 1,500 Volts DC, Nominal. Article 490 was relocated to become Article 495. Its title was revised to “Equipment Over 1,000 Volts AC, 1,500 Volts DC, Nominal” from “Equipment Over 1,000 Volts, Nominal.” This move is part of an effort to institute common numbering of articles with the intent that all articles that cover installations of over 1,000V AC or 1,500V DC have an article number that ends in the digit 5 (XX5).
500.1 Scope. Article 500’s scope was updated to reflect only what the article covers. As previously written, it contained five articles’ scopes, which was a violation of the NEC Style Manual. This multi-article scope had been in the NEC since the 1959 edition. Article 500 covers some of the general requirements that apply to classification of hazardous (classified) locations, and it differentiates requirements by class and division. It had previously also covered some general requirements for the zone classification systems. Combustible fibers/flyings has been added to the list of fire or explosion hazards.
The zone-related information was removed from Article 500. Requirements for zones are based on a classification system developed by the International Electrotechnical Commission, which is covered in articles 505 and 506.
500.4 Documentation. The requirements for documentation of the classification have been improved. The documentation now extends to those areas determined to be unclassified, which are typically adjacent to Division 2 locations. The documentation for hazardous (classified) locations must include an area classification drawing, which must clearly indicate the boundaries between the classified and unclassified areas. This documentation must be available to the authority having jurisdiction and those authorized to design, install, inspect, maintain or operate electrical equipment at the location.
500.5(D) Class III Locations. The changes in 500.5(D) are the first major changes in Class III location definitions in over 40 years. The definition previously stated that Class III locations are those “in which such fibers/flyings are not likely to be in suspension in the air in quantities sufficient to produce ignitible mixtures.” That language was deleted. The new descriptions align with the definitions of Class II locations. A Class III, Division 1 location is now recognized as “a location where combustible fibers/flyings or ignitible fibers/flyings are in the air under normal operating conditions in quantities sufficient to produce explosive or ignitible mixtures.” It also recognizes Division 1 locations as those where mechanical failure or abnormal equipment operation might cause combustible or ignitible fibers/flyings to be produced and also provide a source of ignition through simultaneous failure of electrical equipment, which is consistent with the Class II, Division 1 definition.
A Class III, Division 2 location is often one in which nonmetal combustible fibers/flyings can be released through the abnormal equipment operation, or they may be present and will not normally interfere with the operation of equipment but could become suspended through infrequent malfunctions. It would also include locations where accumulations of fibers/flyings on or in the vicinity of electrical equipment could be sufficient to interfere with heat dissipation, which could permit ignition.
500.6(C) and (D) Class III Combustible and Ignitible Fibers/Flyings. These new sections provide information that differentiates between combustible fibers/flyings and ignitible fibers/flyings. This information is based on changes to NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, which has been expanded to include classification of areas in which combustible or ignitible fibers/flyings are present.
The definitions of “combustible fibers/flyings” and “ignitible fibers/flyings” have been added to Article 100. Section 500.6(C), on combustible fibers/flyings, and 500.6(D), on ignitible fibers/flyings note that there is no further classification into groups of either combustible or ignitible fibers/flyings.
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About The Author
EARLEY, P.E., is an electrical engineer. Retired from the National Fire Protection Association, he was secretary of the National Electrical Code Committee for 30 years and is president of Alumni Code Consulting Group.