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.Exception: In industrial and commercial buildings where conditions of maintenance and supervision en~urf!. , that only qualified persons will service the installation and the entire length of the interior metal water pipe that is being used for the conductor is exposed. rc~wil FPN: See Sections 547-8 and 547-9 for special grounding and bonding requirements for agricultural buildings. (a ) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 10ft (3.05 m) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or sections or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. i C___a~ (1) Continuity. Continuity of the grounding path or the bonding connection to interior piping shall not rely on water meters or filtering devices and similar equipment. (2) Supplemental Electrode Required. A metal underground water pipe shall be supplemented by an additional electrode of a type specified in Sections 250-50 or 250-52. Where the supplemental electrode is a made electrode of the rod, pipe, or plate type, it shall comply with Section 250;.56. The supplemental electrode shall be permitted to be bonded to the grounding electrode conductor, the grounded service-ep.trance conductor, the nonflexible grounded service raceway, or any grounded service enclosure. ii~a;il Exception: The supplermmtal electrode shall be permitted to be bonded to the interior metal water piping at any convenient point as covered in Section 250-50, Exception. Where the supplemental electrode is a made electrode as in Section 250-52(c) or (d), that portion of the bonding jumper that is the sole connection to the supplemental grounding electrode shall not be required to be larger than No.6 copper wire or No.4 aluminum wire.J'C"~~i (b) Metal Frame of the Building or Structure. The metal frame of the building or structure, where effectively grounded. (c) Concrete-Encased Electrode. An electrode encased by at least 2 in. (50.8 mm) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 20 'ft (6.1 m) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than ~-in. (12.7-mm) diameter, or consisting of at least 20 ft (6.1 m) of bare copper conductor not smaller than No.4. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means. ,~.;t-;;Z-i (d) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth at a depth below the earth's surface of not less than 2lh ft (762 mm), consisting of at least 20 ft (6.1 m) of bare copper. conductor not smaller than No.2. .~"iI ..410-57. Receptacles in Damp or Wet Locations (a) Damp Locations. A receptacle installed outdoors in a location protected from the weather or in other damp locations shall have an enclosure for the receptacle that is weatherproof when the receptacle is covered (attachment plug cap not inserted and receptacle covers closed). An installation suitable for wet locations shall also be considered suitable for damp locations. A receptacle shall be considered to be in a location protected from the weather where located under roofed open