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..250-60. Use of Air Terminals Air terminal conductors and driven pipes, rods, or other made electrodes used for grounding air terminals shall not be used in lieu of the made grounding electrodes required by Section 250-52 for grounding wiring systems and equipment. This provision shall not prohibit the required bonding together of grounding electrodes of different systems. FPN No.1: See Section 250-106 for spacing from air terminals. See Sections 800-40(d), 810-210), and 820-40(d) for bonding of electrodes. FPN No.2: Bonding together of all separate grounding electrodes will limit potential differences between them and between their associated wiring systems. . . 250-62. Grounding Electrode Conductor Material The grounding electrode conductor shall be of copper, aluminum, or copper-clad aluminum. The material selected shall be resistant to any corrosive condition existing at the installation or shall be suitably protected against corrosion. The conductor shall be solid or stranded, insulated, covered, or bare. . . 250-64. Grounding Electrode Conductor Installation Grounding electrode conductors shall be installed as specified in (a) through (e). (a) Aluminum or Copper-Clad Aluminum Conductors. Insulated or bare aluminum or copper-clad aluminum grounding conductors shall not be used where in direct contact with masonry or the earth or where subject to corrosive conditions. Where used outside, aluminum or copper-clad aluminum grounding conductors shall not be installed within 18 in. (457 mm) of the earth. (b) Grounding Electrode Conductor. A grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried. A No.4 copper or aluminum, or larger conductor shall be protected if exposed to severe physical damage. A No.6 grounding conductor that is free from exposure to physical damage shall be permitted to be run along the surface of the building construction without metal covering or protection where it is securely fastened to the construction; otherwise, it shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor. Grounding conductors smaller than No.6 shall be in rigid metal conduit, intermediate metal conduit, rigid nomrietallic conduit, electrical metallic tubing, or cable armor. (c) Continuous. The grounding electrode conductor shall be installed in one continuous length without a splice or joint, unless spliced only by irreversible compression-type connectors listed for the purpose or by the exothermic welding process"C~t:;;~1 Exception: Busbars shall be permitted to have splices. (d) Grounding Electrode Conductor Taps. Where a service consists of more than a single enclosure as permitted in Section 230-40, Exception No.2, it shall be permitted to connect taps to the grounding electrode conductor. Each such tap conductor shall extend to the inside of each such enclosure. The grounding electrode conductor shall be sized in accordance with Section 250-66, but the tap conductors shall be permitted to be sized in accordance with the grounding electrode conductors specified in Section 250-66 for the largest conductor serving the respective enclosures. The tap conductors shall be connected to the grounding electrode conductor in such a manner that the grounding electrode conductor remains without a splice or J' oint .'....""'..'.....'..".,."'."'."'.,.."'~$' 'C_entarltw: