2017 NEC: Grounding, Bonding And Wiring—Significant Changes in the 2017 NEC, Part 4

By Michael Johnston | Nov 15, 2016




This article is part 4 in a series that reviews some of the more significant revisions and new requirements in the next National Electrical Code (NEC). Part 4 provides a review of some significant changes in articles contained in Chapter 2, Wiring and Protection, and Chapter 3, Wiring and Methods and Materials.
 Visit for this full series.

Article 250—Grounding 
and Bonding
250.30(A)(4) Electrode

Section 250.30(A)(4) has been revised and simplified, and Exception No. 1 was deleted. There is no longer a hierarchy of electrodes that must be used for grounding separately derived systems. The revision clarifies that the building grounding electrode system must be used when establishing a grounding electrode for a separately derived system. If installed outdoors, the grounding electrode for the separately derived system must comply with 250.30(C).

250.104(A) Metal Water Piping

Section 250.104(A) has been revised by adding “if or sufficient size” to (A)(3) and (A)(4). The wording “that is interconnected to form a building frame” has been added to subdivisions (C) and (D). The minimum bonding conductor or jumper sizes must be in accordance with Table 250.102(C)(1) rather than 250.66.

250.122(F)(2) Multi-conductor Cables

Section 250.122(F)(2) has been revised and arranged in a list format. The revisions address minimum sizes for equipment grounding conductors (EGCs) in multiconductor cables in 
parallel arrangements. A single EGC in each cable can be connected in parallel at each end and connected to a full-size EGC sized based on the overcurrent protection device for the entire circuit.

Article 300—General Requirements for Wiring 
Methods and Materials
300.5(D) Protection From Damage

Electrical metallic tubing (EMT) has been added to the list of raceways permitted to provide physical protection for direct-buried conductors and cables emerging from grade EMT, and associated elbows, couplings and fittings are permitted to be installed in concrete, in direct contact with the earth, approved as suitable for the condition. Section 358.10(B) requires that, where EMT is used in this manner, it must be where protected by corrosion protection and approved as suitable for the condition.

300.5(G) Raceway Seals

The general requirements of first-level subdivision 300.5(G) are now correlated with sections 225.27 and 230.8. Where necessary, spare or unused raceways shall also be sealed. The type of sealants applied must be identified for use with the cable insulation, conductor insulation, bare conductor, shield or other components.

300.22(B) Ducts Specifically Fabricated for Environmental Air

A new exception in 300.22(B) correlates requirements for wiring in ducts specifically fabricated for environmental air between the NEC and NFPA 90A. NFPA 90A permits cables that are “directly associated with the air distribution system” and not to “exceed four feet.” This revision correlates existing requirements within the NEC. For example, in Chapter 8, first-level subdivision 800.113(B) contains the same permission.

Table 310.15(B)(3)(c)

Table 310.15(B)(3)(c), containing rooftop temperature correction factors, has been deleted. Raceways or cables must be installed a minimum distance of ⅞-inch above the roof. Where installed less than ⅞-inch above the roof to the bottom of the raceway or cable, use a temperature adder of 60°F.

314.27(E) Separable Attachment Fittings

New subdivision (E) permits a new product referred to as a “separable attachment fitting.” This product is a listed locking support and mounting receptacle used in combination with compatible attachment fittings designed for the support of luminaires, paddle fans and so forth. These devices are designed to facilitate quick and easy interchange of luminaires or other equipment.

328.14 Installation

Section 328.14 requires type MV cable to be installed, terminated and tested by qualified people. NECA 600 2014, Standard for Installing and Maintaining Medium-Voltage Cable, has been added to the Informational Note. It provides valuable information on installation requirements, guidelines for qualified installers, cable splicing and more.

The next article will be in the December issue. For more information and to view all the proposed revisions, please 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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