Continuing With Special Occupancies: Accepting (NEC) change, part 15

By Mark Earley | Apr 14, 2023
Our review of the updates to Chapter 5 in the 2023 National Electrical Code continues.

Our review of the updates to Chapter 5 in the 2023 National Electrical Code continues.

517.30 Sources of Power. Section 517.30 has been rewritten to clarify that the essential electrical system (EES) is required to have two or more independent sources or sets of sources that supply the entire load. At least one of the sources or sets of sources is required to be located entirely on-site. The other source(s) or set(s) of sources must also be capable of supplying the entire EES load. The other sources or sets of sources are permitted to be located on- or off-site. This change permits the healthcare facility to be responsible for all sources and makes them independent of the local utility. 

The term “normal source” is no longer used, because there is no meaningful distinction between a normal source and an essential system source. The EES at some facilities requires multiple feeders and sources to ensure reliable power. New requirements have been added for healthcare facility microgrids, which are permitted as a normal source or alternate source, but cannot function as both.

517.41 Required Power Sources. Section 517.41 has been rewritten, and it now correlates with 517.30. The requirements in this section apply to nursing homes and limited-care facilities.

Article 517, Part V. Diagnostic Imaging and Treatment Equipment. The title of Part V of Article 517 has been changed from “X-Ray Installations” to “Diagnostic Imaging and Treatment Equipment” to recognize the many types of imaging equipment.

517.80 Patient Care Spaces. Class 2 and Class 3 signaling and communications systems and power-limited fire alarm systems are not required to comply with the grounding requirements in 517.13 and the mechanical protection requirements of 517.31(C)(3)(5), or to be enclosed in raceways. “Class 2 circuits that transmit power and data to a powered device” are also now exempt from the requirements of 517.13.

518.2(A) Examples. Casinos and gaming facilities have been added to the list of assembly occupancies Article 518 covers.

518.4 Wiring MethodsGeneral. Power over ethernet (PoE) is now permitted to supply lighting in assembly occupancies. An informational note was added that references the NEMA standard for the installation of PoE lighting. The wiring methods for buildings or portions of buildings of nonfire-rated construction were expanded to include the permitted Chapter 3 wiring methods.

520.53(C) Construction. While they have some things in common with general-­purpose switchboards, portable stage switchboards cannot comply with 408.18, which was written for general-purpose ones. The listing for portable stage switchboards prohibits work of any kind on connections while the switchboard is energized.

520.68(D) Special-Purpose Multi-­Circuit Cable Systems. A new 520.68(D) has been added for special-purpose multicircuit cable systems. Branch circuits must not exceed 20A and 150V to ground. Trunk cables, breakout assemblies and multicircuit enclosures are required to be listed.

Article 530 Motion Picture and TV Studios and Remote Locations. Article 530 has been completely rewritten. The technology used in the production of movies and television programs has undergone considerable changes in recent years. Many technologies formerly covered in the article have been phased out, including some lighting. Studio cameras are smaller and much more energy-­efficient. Their light-gathering ability also reduces the need for high-energy lighting.

545.22 Power Supply. This section was revised to clarify that relocatable structures must be supplied by a feeder. This correlates with Article 550, which doesn’t allow service equipment on a structure without a permanent foundation. Two or more relocatable structures joined into a single unit are permitted to use a chassis bonding conductor as the tap conductor.

547.26 Physical Protection. Section 547.26 has been revised to prohibit nonmetallic sheathed cable from being concealed within walls and above ceilings of a building or portions thereof that are contiguous with or physically adjoined with livestock areas.

547.44(B) Bonding of Equipotential Planes. The bonding requirements in agricultural buildings have been clarified. Equipotential planes must be bonded to the grounding electrode system or an equipment grounding terminal in any panelboard associated with the equipotential plane. The bonding conductor must be a solid, copper, insulated, covered or bare conductor no smaller than 8 AWG.

550.10(I) Mast Weatherhead or Raceway. The reference to Article 230 was clarified to specify that Part II applies. This section has been clarified to indicate that the permitted metal raceways are rigid metal conduit or intermediate metal conduit. In addition, this section now recognizes rigid polyvinyl conduit or other raceways suitable for the location.

550.16(C)(1) Exposed Non-Current-Carrying Metal Parts. Mobile homes often consist of multiple sections. This section requires that the chassis of multiple mobile home sections must be bonded together with a solid 8 AWG copper conductor. The permitted connection methods are specified in 250.8. Section 250.12 requires that the surfaces of equipment to be bonded must be cleaned at the point of contact by removing nonconductive coatings to ensure electrical continuity.

550.32(A) Mobile Home Service Equipment. Section 550.32(A) requires mobile home service equipment to be located adjacent to the mobile home. It is prohibited from being mounted in or on the mobile home. The disconnecting means was previously required to be located in sight from and not more than 30 feet from the exterior wall of the home; the distance is no longer specified in the requirement. However, the service equipment is required to be in a readily accessible outdoor location that is in sight from the mobile home it serves.

The term “in sight from” is defined in Article 100 as follows: “Equipment that is visible and not more than 15 m (50 ft.) distant from other equipment is in sight from that other equipment.” This establishes 50 ft. as the new maximum distance from the mobile home.

550.33(A) Feeder Equipment. A new Section 550.33(A) has been added. The previous 550.33(A) became (B). Neither service equipment nor the feeder assembly is permitted to be mounted in or on a mobile home. A manufactured home feeder disconnecting means is permitted to be installed in or on the manufactured home in accordance with 550.33(B).

551.3 Electrical Datum Plane Distances. Electrical datum plane requirements were added to Article 551 because RV parks often border bodies of water. In areas subject to tidal fluctuations, the datum plane is 2 feet above the highest high-tide level under normal conditions. In areas not subject to tidal fluctuation, the plane is 2 feet above the highest water level under normal conditions.

551.40(D) Loss of Ground Device. The previous 551.40(D), “Reverse Polarity Device,” was deleted. The reverse polarity device may only indicate that the pedestal is miswired, but may not interrupt power. A new 551.40(D) was added to require a listed grounding monitor interrupter to be installed between the feeder assembly connection to the vehicle and before either a transfer switch (if installed) or the panelboard.

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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.





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