There were 3,688 proposals for changes to the National Electrical Code (NEC) and 2,349 comments processed by the National Fire Protection Association (NFPA) staff at NFPA headquarters in Quincy, Mass. The following is part five in a series of significant changes for the 2008 NEC. Part one appeared in the July 2007 issue of ELECTRICAL CONTRACTOR, part two in October 2007, part three in March 2008, and part four in April 2008.

The 2008 NEC was formally adopted in August 2007, and new copies were available from the National Electrical Contractors Association (NECA) and the National Fire Protection Association (NFPA) as of September 2007.

The following are some of the most important changes. Strikethrough text shows deletions, and underlined text shows additions. Commentary denoted by red text also follows some changes for explanation.

2005 NEC—250.52 Grounding Electrodes.

(A) Electrodes Permitted for Grounding.

(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.5 2.44 m (8 ft.) in length and shall consist of the following materials.

(a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size ¾) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.

(b) Electrodes of rods of iron or steel shall be at least 15.87 mm (? in.) in diameter, unless Stainless steel rods less than 16 mm (? in.) in diameter, nonferrous rods, or their equivalent shall be listed and shall not be less than 13 mm (½ in.) in diameter.

2008 NEC—250.52 Grounding Electrodes.

(A) Electrodes Permitted for Grounding.

(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.44 m (8 ft.) in length and shall consist of the following materials.

(a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size ¾) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.

(b) Grounding electrodes of stainless steel, copper or zinc coated steel shall be at least 15.87 mm (? in.) in diameter, unless listed and not less than 12.70 mm (½ in.) in diameter.

Copper and zinc-coated rods are both produced from the same “ferrous” steel core and coated with the appropriate “non-ferrous” coating (copper or zinc). The new text recognizes listed stainless steel-, copper- and zinc-coated ground rods that are not smaller than ½ inch in diameter.

2005 NEC—250.54

Supplementary Grounding Electrodes.

Supplementary grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.56, but the earth shall not be used as an effective ground-fault current path as specified in 250.4(A)(5) and 250.4(B)(4).

2008 NEC—250.54

Auxiliary Grounding Electrodes.

One or more grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.56, but the earth shall not be used as an effective ground-fault current path as specified in 250.4(A)(5) and 250.4(B)(4).

The two terms, “supplemental” and “supplementary” are synonymous in the English language. It is easier to distinguish between the two concepts if the term used to define the type of electrode function specified in 250.54 was changed to auxiliary.

2005 NEC—250.56

Resistance of Rod, Pipe, and Plate Electrodes.

A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(2) through (A)(7). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft.) apart.

2008 NEC—250.56

Resistance of Rod, Pipe, and Plate Electrodes.

A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft.) apart.

The requirement for a single electrode that does not have a resistance of 25 ohms or less to be augmented does not apply to any electrodes other than rod, pipe or plate. It is required to augment such an electrode with one additional electrode of any of the types specified by 250.52(A)(4) through 250.52(A)(8) so 250.52(A)(1) for underground metal water pipes, 250.52(A)(2) for metal frame of a building or structure, and 250.52(A)(3) for concrete-encased electrodes were deleted from the list of permissible electrodes to be used for augmenting the rod, pipe or plate electrodes.

2005 NEC—250.64

Grounding Electrode Conductor Installation.

(D) Grounding Electrode Conductor Taps. Where a service consists of more than a single enclosure as permitted in 230.71(A), it shall be permitted to connect taps to the common grounding electrode conductor. The common grounding electrode conductor shall be sized in accordance with 250.66, based on the sum of the circular mil area of the largest ungrounded service entrance conductor(s). Where more than one set of the service entrance conductors as permitted by 230.40, Exception No. 2 connect directly to a service drop or service lateral, the common grounding electrode conductor shall be sized in accordance with Table 250.66, Note 1. Each such tap conductor shall extend to the inside of each such enclosure. The grounding electrode conductor taps shall be sized in accordance with 250.66 for the largest conductor serving the individual enclosure. The tap conductors shall be permitted to be sized in accordance with the grounding electrode conductors specified in 250.66 for the largest conductor serving the respective enclosures. The tap conductors shall be connected to the common grounding electrode conductor in such a manner that the common grounding electrode conductor remains without a splice or joint.

2008 NEC—250.64

Grounding Electrode Conductor Installation.

(D) Service with Multiple Disconnecting Means Enclosures. Where a service consists of more than a single enclosure as permitted in 230.71(A), grounding electrode connections shall be made in accordance with (1), (2) or (3).

(1) Grounding Electrode Conductor Taps. Where the service is installed as permitted by 230.40, Exception No. 2, a common grounding electrode conductor and grounding electrode conductor taps shall be installed. The common grounding electrode conductor shall be sized in accordance with 250.66, based on the sum of the circular mil area of the largest ungrounded service entrance conductor(s). Where the service entrance conductors connect directly to a service drop or service lateral, the common grounding electrode conductor shall be sized in accordance with Table 250.66, Note 1.

A tap conductor shall extend to the inside of each service disconnecting means enclosure. The grounding electrode conductor taps shall be sized in accordance with 250.66 for the largest conductor serving the individual enclosure. The tap conductors shall be connected to the common grounding electrode conductor by exothermic welding or with connectors listed as grounding and bonding equipment in such a manner that the common grounding electrode conductor remains without a splice or joint.

(2) Individual Grounding Electrode Conductors. A grounding electrode conductor shall be connected between the grounded conductor in each service equipment disconnecting means enclosure and the grounding electrode system. Each grounding electrode conductor shall be sized in accordance with 250.66 based on the service-entrance conductor(s) supplying the individual service disconnecting means.

(3) Common Location. A grounding electrode conductor shall be connected to the grounded service conductor(s) in a wireway or other accessible enclosure on the supply side of the service disconnecting means. The connection shall be made with exothermic welding or a connector listed as grounding and bonding equipment. The grounding electrode conductor shall be sized in accordance with 250.66 based on the service-entrance conductor(s) at the common location where the connection is made.

Section 250.64(D) has been expanded to deal with grounding electrode conductor installation requirements for multiple disconnecting enclosures. Reworded 250.64(D)(1) contains installation requirements for two to six individual disconnects where the main grounding electrode conductor is installed under the disconnecting means with individual grounding electrode taps connected into each enclosure. New 250.64(D)(2) was added to permit individual grounding electrode conductors to be installed to each individual disconnecting means enclosure. New 250.64(D)(3) was added to include the provision in 250.24 for making the grounding electrode connection at an accessible location on the load side of the service drop or service lateral.

2005 NEC—250.68

Grounding Electrode Conductor and Bonding Jumper Connection to Grounding Electrodes.

(A) Accessibility. The connection of a grounding electrode conductor or bonding jumper to a grounding electrode shall be accessible.

Exception No. 2: An exothermic or irreversible compression to fireproofed structural metal shall not be required to be accessible.

2008 NEC—250.68

Grounding Electrode Conductor and Bonding Jumper Connection to Grounding Electrodes.

(A) Accessibility. All mechanical elements used to terminate a grounding electrode conductor or bonding jumper to a grounding electrode shall be accessible.

Exception No. 2: Exothermic or irreversible compression connections used at terminations, together with the mechanical means used to attach such terminations to fireproofed structural metal whether or not the mechanical means is reversible, shall not be required to be accessible.

The main rule was changed to indicate that all mechanical connections of a grounding electrode conductor must be accessible after installation. Section 250.68, Exception No. 2 was revised to permit the mechanical means, such as a nut and bolt, used to connect irreversible compression connectors to the metal structure to not be accessible.

ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at mark.c.ode@us.ul.com. JAMES G. STALLCUP is the CEO of Grayboy Inc., which develops and authors publications for the electrical industry and specializes in classroom training on the NEC and OSHA, as well as other standards. Contact him at 817.581.2206. JAMES W. STALLCUP is vice president and senior editor at Grayboy.