14E-2-250 Grounding and bonding.

The provisions of Article 250 of NFPA 70 are adopted by reference with the following modifications:

1.   Revise section 250.58 to read:

"Common Grounding Electrode System for High-Rise Buildings and Similar Buildings or Structures of Large Area. In high rise buildings and in similar buildings or structures that cover a large area, a common grounding electrode conductor, which will be considered an extension of the building grounding electrode, shall be permitted to be used as the required grounding electrode for all separately derived systems and communications systems. The common grounding electrode conductor shall originate at an approved connection on the street side of the incoming metallic water pipe.

Informational Note: See Figure 250.58 – Common Grounding Electrode System which is also known as Hogan Ground.

The common grounding electrode system installation shall comply with 250.58(A) through (C).

(A)   Size. The common grounding electrode system conductor shall be sized in accordance with Table 250.66 based on the largest service or separately derived system using the common grounding electrode conductor. The minimum size of the common grounding electrode system conductor shall be 4/0 AWG copper installed in a 1-1/4" metal raceway permitted by 250.64(B). The maximum size of the common grounding electrode system conductor shall be 500 kcmil AWG copper installed in a 1-1/2" metal raceway permitted by 250.64(B).

(B)   Splices and Taps. The common grounding electrode conductor shall be continuous through its entire length. Where a splice is necessary, it shall be made by the use of listed irreversible compression connectors or exothermic welding. The tap connections shall be made to aluminum or copper busbars not smaller than 1/4 in. × 2 in. If aluminum busbars are used, the installation shall comply with 250.64(A).

(C)   Approved Metal Junction Boxes. All splices and taps of the common grounding electrode system conductor shall be made in and bonded to an approved metal junction box. The metal junction box shall be mounted on or bonded to the nearest available structural member of the building."

2.   Insert new figure 250.58 High Rise Common Ground Electrode System:

3.   Revise subsection 250.64(B) to read:

"Securing and Protection Against Physical Damage. Where exposed, a grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried. All grounding electrode conductors shall be installed in rigid metal conduit (RMC), intermediate metal conduit (IMC), or electrical metallic tubing (EMT) in accordance with Table 250.66. Raceways for grounding electrode conductors shall not contain other conductors.

Grounding electrode conductors and grounding electrode bonding jumpers in contact with the earth shall not be required to comply with 300.5, but shall be buried or otherwise protected if subject to physical damage."

4.   Revise subsection 250.64(C) to read:

"Continuous. Except as provided in 250.30(A)(5) and (A)(6), 250.30(B)(1), and 250.68(C), grounding electrode conductor(s) shall be installed in one continuous length without a splice or joint. If necessary, splices or connections shall be made as permitted in (1) through (2):

(1)   Splicing of the wire-type grounding electrode conductor shall be permitted only by irreversible compression-type connectors listed as grounding and bonding equipment or by the exothermic welding process.

(2)   Sections of busbars shall be permitted to be connected together to form a grounding electrode conductor."

5.   Revise the second paragraph of subsection 250.64(D)(1):

"A grounding electrode conductor tap 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 service-entrance conductor serving the individual enclosure. The tap conductors shall be connected to the common grounding electrode conductor by one of the following methods in such a manner that the common grounding electrode conductor remains without a splice or joint:

(1)   Exothermic welding.

(2)   Connectors listed as grounding and bonding equipment.

(3)   Connections to an aluminum or copper busbar not less than 1/4 in. × 2 in. The busbar shall be securely fastened in a metal box and shall be installed in an accessible location. Connections shall be made by a listed connector or by the exothermic welding process. If aluminum busbars are used, the installation shall comply with 250.64(A)."

6.   Revise subsection 250.64(F)(3) to read:

"Bonding jumper(s) from grounding electrode(s) shall be permitted to be connected to an aluminum or copper busbar not less than 1/4 in. thick × 2 in. wide and of sufficient length to accommodate the number of terminations necessary for the installation. The busbar shall be securely fastened and shall be installed in a metal box and at an accessible location. Connections shall be made by a listed connector or by the exothermic welding process. The grounding electrode conductor shall be permitted to be run to the busbar. Where aluminum busbars are used, the installation shall comply with 250.64(A)."

7.   Revise table 250.66 to read:

Size of Largest Service-Entrance Conductor or Equivalent for Parallel Conductor(s)		Size of Grounding Electrode Conductor and Conduit or Tubing
Copper	Aluminum	Copper	Conduit or Tubing	Aluminum	Conduit or Tubing
Up to 2	Up to 1/0	8	1/2 in.	6	1/2 in.
Up to 1/0	Up to 3/0	6	1/2 in.	4	3/4 in.
Up to 3/0	Up to 250	4	3/4 in.	2	3/4 in.
Up to 350	Up to 500	2	3/4 in.	1/0	1 in.
Up to 600	Up to 900	1/0	1 in.	3/0	1 in.
Up to 1,100	Up to 1,750	2/0	1 in.	4/0	1 in.
Up to 1,300	Up to 2,000	3/0	1 in.	250	1-1/4 in.
Up to 1,700	Up to 2,400	4/0	1 in.	300	1-1/4 in.
Up to 1,700	Up to 2,800	250	1-1/4 in.	350	1-1/4 in.
Up to 2,000	Up to 3,200	300	1-1/4 in.	400	1-1/2 in.
Up to 2,400	Up to 4,000	350	1-1/4 in.	500	1-1/2 in.
Up to 2,800	Up to 4,800	400	1-1/2 in.	600	2 in.
Up to 3,200	Up to 5,600	500	1-1/2 in.	700	2 in.

 

(Amend Coun. J. 11-8-17, p. 59720, § 14)