2017 NEC: Chemicals, Fuels And Hazardous Locations—Significant Changes in the 2017 NEC, Part 7

By Michael Johnston | Feb 15, 2017




Before we proceed, in part 3 of this series, the change in Section 230.70(A)(4) dealing with service disconnects on one- and two-family dwellings was reversed during the late stages of the development process and never made it into the 2017 National Electrical Code (NEC). We thank our astute readers who pointed it out.

Moving on, this article wraps up Chapter 4 and reviews some significant changes in Chapter 5, Special Occupancies.
 Visit for this full series.

480.3 Listing of Batteries and Management Equipment

Section 480.3 is new and requires all batteries and their associated battery management equipment to be listed. The listing requirement excludes lead-acid-type batteries. Catastrophic failures in new battery technology systems mandate rigorous testing for safety.

500.2 Definitions

Multiple definitions previously located in 500.2 have been relocated to Art-
icle 100.

Section of the NEC Style Manual requires that, if a term appears in more than two articles, it shall be included in Article 100. The words “as applied to Hazardous (Classified) Locations” have been added in brackets following each relocated defined term.

500.5(A) Ammonia Areas are permitted to be Unclassified

The title of Subdivision (A) has been changed from “Classifications of Locations” to “General.” Classification of ammonia system refrigerant machinery rooms has been revised and clarified based on provided ventilation. Ammonia areas provided with adequate, continuous mechanical ventilation or initiation by a detection system at concentrations not exceeding 150 parts per million shall be permitted to be as unclassified locations. Section 505.5(A), covering the hazardous location classification zone system, includes a similar revision.

505.15(A) New Limits for Protection Techniques in Zone 0 Locations

Section 505.15(A) provides requirements for allowable wiring methods in Class I, Zone 0 locations. The previous allowance for all intrinsically safe wiring methods in accordance with Article 504 has been reduced. Type “ia” intrinsically safe circuits and type “ma” encapsulation are suitable protection techniques for installations in Zone 0 hazardous locations.

511.3(D) Classification of Locations in Commercial Repair Garages

Section 511.3(D) has been revised and titled “Repair Garages, Major.” This subdivision and new associated Table 511.3(D) provide area classification for major repair garages that use lighter-than-air gaseous fuels. The new informational note provides a reference to NFPA 30A and Table 8.3.2, the origin of these area classification requirements.

511.8 Underground Wiring

A new Section 511.8, Underground Wiring, and an exception have been added. The driving text requires either threaded rigid metal conduit or intermediate metal conduit. The exception permits nonmetallic wiring methods under restrictive conditions dealing with depth, transitions to metallic conduit methods and installing an equipment grounding conductor.

514.3(B)(3) Storage Tank 
Area Classifications

A list item (3) in Section 514.3(B) is new and addresses liquefied natural gas (LNG), compressed natural gas (CNG), and liquefied petroleum gas (LPG) storage tank areas and locations. The new requirements provide separation distances from property lines and from other gas storage tanks. Table 514.3(B)(2) is referenced from this new list item for establishing classification of areas containing CNG, LNG or LPG storage or dispensing operations.

514.11 Emergency Disconnects for Motor Fuel Dispensing Equipment

Section 514.11 has been revised to align with the requirements in NFPA 30A 2015. Subdivision (A) now addresses only emergency disconnects for dispensing equipment and no longer addresses circuit maintenance disconnects and breaking all conductors of the circuit(s). Section 514.13 still provides these requirements. Subdivisions (B) and (C) address locations of disconnects for attended and unattended dispensing facilities, respectively.

Article 516 Rewritten

Article 516, Spray Application, Dipping, Coating, and Printing Processes Using Flammable or Combustible Materials, has been rewritten to align more closely with NFPA 33 and 34 including extracted material. The rewrite includes organizing the previous requirements into separately titled parts of Article 516. The revisions provide a more logical layout, which enhances usability, and more consistency with NEC Style Manual requirements.

Next month’s column will look at several key revisions for healthcare facilities in addition to more revisions in Chapter 5. For more detailed information and to view all of the proposed revisions, visit

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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