New Definitions and Revisions: Significant Changes in the 2020 NEC, Part 2

By Michael Johnston | Jul 15, 2019
Washing Machine Laundry Image by Steve Buissinne from Pixabay
This article focuses on defined terms that have been revised and new definitions that have been added in the 2020 edition of the National Electrical Code. 

Last month, Part 1 of this series focused on general revisions in the introduction and provided a look at some new articles added in the 2020 National Electrical Code (NEC) . As this series continues, it will provide the NEC revisions in sequence. This article focuses on defined terms that have been revised and new definitions that have been added in this edition of the Code. Definitions in the NEC are arranged in three parts of Article 100.

Article 100 Definitions of Fault Current and Fault Current, Available

New definitions of the terms “fault current” and “fault current, available” have been added to Article 100. This revision aligns with similar recent revisions in other standards that use the terms, such as NFPA 70E, Standard for Electrical Safety in the Workplace.

Fault Current: The current delivered at a point on the system during a short-circuit condition. (Code Making Panel-10)

Fault Current, Available (Available Fault Current): The largest amount of current capable of being delivered at a point on the system during a short-circuit condition. (CMP-10)

Article 100 Habitable Room

A new definition of the term “habitable room” has been added to Article 100. The definition describes what constitutes a habitable room and differentiates it from one that is not. The new definition aligns with the same defined term in NFPA 5000 with similar context to the defined term in the International Residential Code and International Building Code.

Habitable Room: A room in a building for living, sleeping, eating, cooking, but excluding bathrooms, toilet rooms, closets, hallways, storage or utility spaces, and similar areas. (CMP-2)

Article 100 Labeled—Informational Note Added

A new informational note has been added following the definition of the term “Labeled.” Clarification has been provided about what constitutes labeling as the NEC defines. The labeling can appear on the smallest package of the product in cases where the equipment is small or installed in a harsh environment.

Informational Note: If a listed product is of such a size, shape, material or surface texture that is not possible to legibly apply the complete label to the product, the complete label may appear on the smallest unit container in which the product is packaged.

Article 100 Laundry Area

A new definition of the term “Laundry Area” has been added to Part I of Article 100. The definition formerly found in Section 550.2 is no longer necessary and has been deleted.

Laundry Area: An area containing or designed to contain a laundry tray, clothes washer or clothes dryer. (CMP-2)

Article 100 Messenger or Messenger Wire

A definition of the terms “messenger” and “messenger wire” have been added to Article 100. This unique definition applies to either term used within the NEC. A messenger can be current-carrying or be dead-ended on both ends and used only for support.

Messenger or Messenger Wire: A wire that is run along with or integral with a cable or conductor to provide mechanical support for the cable or conductor. (CMP-6)

Article 100 Prime Mover

An example of a prime mover is the engine that drives the electric generator on a generator set.

Prime Mover: The machine that supplies mechanical horsepower to a generator. (CMP-13)

Article 100 Reconditioned

A new definition of the term “reconditioned” has been added in Part I of Article 100. The process of reconditioning equipment differs from normal servicing of equipment that remains in place. The term “reconditioned” and related general requirements were introduced in the 2017 NEC in Section 110.21(A)(2). During the 2020 NEC development process, this term was incorporated in multiple articles that added provisions related to equipment that is either permitted or prohibited from being reconditioned. Accordingly, the NEC process yielded a common definition of the term “reconditioned” and included it in Article 100 in compliance with Section of the NEC Style Manual.

Reconditioned: Electromechanical systems, equipment, apparatus or components that are restored to operating conditions. This process differs from normal servicing of equipment that remains within a facility or replacement of listed equipment on a one-to-one basis. (CMP-10)

Informational Note: The term reconditioned is frequently referred to as rebuilt, refurbished or remanufactured.

Article 100 Service Equipment

The definition of the term “service equipment” has been revised. The word “usually” was removed to reduce ambiguity, and the NEC term “disconnecting means” has replaced the word “cutoff.” Technical responsibility of this definition has been reassigned from CMP-4 to CMP-10.

Service Equipment: The necessary equipment, consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the serving utility and intended to constitute the main control and disconnect of the serving utility. (CMP-10)

This series continues next month.

About The Author

A man, Mike Johnston, in front of a gray background.

Michael Johnston

NECA Executive Director of Codes and Standards

JOHNSTON is NECA’s executive director of codes and standards. He is a member of the NEC Correlating Committee, NFPA Standards Council, IBEW, UL Electrical Council and NFPA’s Electrical Section. Reach him at [email protected].






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