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k;_ _ - -.�...�... .. , , . _.. .-,_: _ : . • � •`";.. -'+ .. .. - � �.��rv-._,�, •ARTICLE 250—OROUNDINO 70-127 7�128 NATIONAL ELECTRICAL CODE jumper shall be sized in accordance with Table 250=95 using the rating of (b) Metel Freme of the Bullding. The metal frame of the building,where , the circuit that may ener�ize the piping. eHectively grounded. � � •�� The equipp�ent groundmg conductor for the circuit that may energize the Fp ; Effective unded means intentio piping shall be permitted to serve as the bonding means. � � lY BCO oa11Y conaectad to earth through a ground connection or connections�of su8'ictentty low impedance and having sug'i- (FPI�• Bonding all pipiag and metal air ducts within the premises will pravide c�ent current-cariying capacity to•prevent the buildup of voltegea thet may result in additional safety. , undue hazard to oonnected equipment or to peisons. H.Grounding Electrode System (c) Concrete-Encesed Electrode..An electrode encased by at least 2 inches(50.8 mm)of concrete,.located witl�in and near the bottom of a oon- 250-ei. Grounding Electrode System. If available on�the remises at �ete foundation or footing that is in direct oontact with the.earth,consist- P mg of at leasf ZO feet (6.1 m) of one or more bare or zinc galvanized or each building or structure served,each item(a)throu�(d)below,and anyl.other electrically wnductive coated stee! reinforcing bazs or rods of not made electrodes in accordance with Sections Z50-8 c and d shall be bonded to ether to form.the � � � �' ��g �an �/2 inch (12.7 mm) diameter, or oonsisting of.at least 20 feet 8 grounding electrode system. Interior metal� (6.1.m)of bare oopper wnductor not smaller t6an No.4. water piping located more than 5 feet(152 cm)hom the point of entrance to the building shall not be used as a conductor to interconnect the eleo- (d) Ground Ring. A ground ring encircling the building or structure, in trodes and the grounding electrode conductor.The bonding jumper shall be direct contact with the earth at a depth below earth surface not less than installed in accordance with Sections 250-92(a) and (b), shall be sized in 2�x feet(762.mm),consisting of at least 20 feet(6.1 m)of.bare copper con- accordance with Section 250-94, and shall be connected in the manner� ductor not smaller than.No.2. – � � specified in Section 250-115.The unspliced grounding electrode conductor "— shall be permitted to run to any convenient grounding electrode available 250-83• Made end.Other Electrodea Where none of the electrodes sPec- in the grounding electrode system.It shall be sized for the largest ground= ��Section 250-S1 is available,one or more of the electrades spec�l'ied ing electrode conductor required among all the available electrodes. in(b)tluou��d)belaw shall be used.Where practicable,maae electrodes Fxception No. 1: It shaU be pernutted to splice the gmunding electrode shall be em ded below permanent moisture level.Made electrodes shall conductor by means of ir�versible compression-type connectors listed for ��ee f�om nonoonductive coatings,such as paint or enamel.Where more , the purpose or the exothemric welding process, than one electrode is used,each electrode of one grounding system(includ- ing that used for lightning rods)shall not be less than 6 feet(1.83 m)from Exception No. 2: In indust�ial and co�rrme�ial buildings whe�condi- �y other electrode of another grounding system. ' tions of maintenance and supervision ensu� that only qualified persons will service the installation and tite entine lengih of the interior metal water ��N): Ttvo or more e(ectrodes Wat are effectively bonded together are to be pipe that is being«sed for the condttctor rs exposed treated as a single electrode system in Wis sepse. ;.•., , (FPI�: See Secdon 547-8 for special grounding and bonding requirements for • Ia) Metal Underground Gas Plping Syatem. A metal underground gas agncultural bui(dings. � pipmg system shall not be used as a grounding electrode. (b) Other Locel Metal Underground Systems or Structures. Other local (a) Metal Underground Weter Plpe. A metal underground water pipe in metal underground systems or structures, such as,piping systems and direct contact with the earth for 10 feet (3.05 m) or more (including any �derground Eanks. metal well casing effectively bonded to the pipe)and electrically continu- . ous(or made electrically continuous bx bond'mg around insulating�oints or �e) Rod end Plpe Electrodea Rod and pipe electrodes shall not be less secdons or insulating pipe).to the pomts of connection of the grounding than 8 feet(2.44 m)in length and shall oonsist of the following materials, electrode wnductor and the bonding conductors.Continuity of the ground- �d shal!be installed in the following manner. , ing path or the bonding wnnecdon to interior piping shall not rely on water (1) Electrodes of pipe or conduit shall not be smaller than�/a-inch trade meters. A metal underground water pipe shall be supplemented by an size and,where of iron or steel,shall have the outer surface galvanized or additional electrode of a type specified in Section 250-81 or in Section 250- otherwise metal-ooated for corr�ion protection. 83. The supplemental electrode shall b� permitted to be bonded to the (2) Electrodes of rods of.iron or steel shall be at least 3'e inch(15.87 mm) grounding electrode wnductor,,the grounded service-entrance conductor, .� ��eter. Stainless steel rods�less than�/8 inch (15.87 mm)'in diameter, the grounded service raceway,or any grounded service endosure. I�nonferrous rods,or their equivalent shall be listed and shall not be less than Wh,�re the supplemental electrode is a made electrode as in Section 250- �/2��1Z,�mm�in diameter. ' ' � " 83(c)or(d),that portion of tlie bonding jumper that is the sole connection �3) The electrode shall be installed such�that at least 8 feet(2.44 m)of to the supplemental�rounding electrode shall not be required to be lazger �ength is in contact with the soil.It shall be driven to a dept6 of not less than No.6 copper w►re or No.4 aluminum wire. � than 8 feet (2.44 m) except that, where rock bottom is encountered, the Fxce,Ption: The supplemental electro�e shaU be pemritted to be bonded. electrode shall be driven at an oblique angle not to exceed 45 degrees from to the mterior metal water prping at airy convenient point as covered in the vertical or shall be buried in a trench that is at least 2�/Z feet(762 mm) Section 250-81, Fzceplion 1Vo. 2. I deep.The upper end of We electrode shall,be flush with or below ground