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_ ._.... . i • . .a tfT`'iti° �"iL' t(` ' t —0'1• — ARTICLE 250—OROUNDINO 70-127 �70-1'28 NATIONAL ELECTRICAL CODE �� jumper shall be sized in accordance wilh Table 250=95 using the rating of (b) Metel Frnme of the Bullding. The metal frame of•the building,where the circuit that may ener�ize�the piping, effectively gtounded. . �� The equipment grounduig conductor for the circuit that may energize the gpN: Effective rounded means intcntio piping sl�all be permitted to.serve,as the bonding means. � � h'B nally oonnected to earth through a ground connection or connections of suHicienUy low impedance and having au[(i- (f PN): Bonding all piping and metal air ducts within the premises will prwide clent current-catrying capacity to�prevent the buildup of volfagee that may tesull in additional sa[ety. , undue hezard to wnnected equipment or to pe�sons. • H.GrourMing�lectrode System (c) Concrete-Encased Elecfrode. An electrode encased by at least 2 inches(50.8 mm)of concrete,.located within and near the bottom•of a oon- 250-81. Grounding Electrode System. If available on the remises at �ete foundation or footing that is in direct oontad with the.earth,consist- P tng of at least 20 feet (6.1 m)of one or more bare or zinc galvanized or each building or structure served,each item(a)thtou�(d)below,and anyl other electrically oonductive wated steel reinfotcing bars or rods of not made electrodes in accordance with Sections 250-5 (c) and (d), shall be less than �/Z inch (12.7 mm) diatneter, or oonsistiog of at least 20 feet bonded together to fonn the grounding electrode system. Interior metal� (6.1 m)of baze wpper wnductor not�smaller than No.4. water piping located more than 5 feet(152 cm)from the point of entrance to the building shall not be used as a conductor to interconnect the elec- (d) Ground Ring. A ground ring encircling the building or structure,in trodes and the grounding electrode conductor.The bonding jumper shall be di�ed 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 Z�z feet(?62 mm),consisting of at least 20 feet(6.1 m)of bare copper wn- accordance witl► Section 'L50-94, 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 arry convenient grounding electrode available 250-83• Made end.Olher Electrodes. Where none of the electrodes sPec- in the grounding ele�trode system.It shall be sized for the largest ground- �fied in Section 25a81 is available,one or more of the electrades spec�fied ing electrode conductor requued among all the available electrodes. in(b)throuQh�d)below shall be used.Where practicable,macle electrodes Exception No. 1: It shaU be perniilted to splice t/ie grouirding electrode shall be embe ded below permanent moisture level.Made electrodes shall conductor 6y means of irneversible con�pression-type corurectors listed for be free fisom nonoonductive coatings,such as paint or enamel.Whete more tl�e purpose or the exothernuc weldu�g process. than one electrode is used,each elect[ode of one grounding system(includ- ing that used for lightning rods)shall not be less than 6 feet(1.83 m)from Ezception No. 2: In industrial and co�nme�ial buildings w/ie�condf- �y other electrode of enother grounding system. ' tions of n�aintennnce and supervision ensure tha� only qualifted persons will service tlre i�rstallation and the entrre length of tiee interior metal water ��N): Two or more electrodes that ere eQectivefy bonded together are to be pipe that rs beuig used for the conductor is orposed. U��d as a single elect�ode system in Wia sense. ,,.. , (FPN): See Section 547-8 for special grounding and bonding requirements tor • ��I Metel Underground �es Plping Syatem. A metal underground gas agncultural buildings. piping system shall not be used es a grounding electrode. (a) Metal Underground Water Pipe. A metal underground water pipe in (b) Oiher Local Metel Underground Systema or Structures. Other local direct contact with the earth for 10 feet (3.05 m) or more mcludin a� metal underground systems or structures, such�as,piping systems and metal well casing effectively bonded to the pipe)and elect�cally continu underground tanks. ous(or made electrically oontinuous b�bond'mg around insulating joints or Ic) Rod end Plpe Eleetrodea Rod and pipe electrodes shall not be less sections 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 conductor and the bonding conductors.Continuity of the ground- and shall be installed in the following manner: ing path or lhe bonding connection to interior piping shall not rely on water (1) Electrodes of pipe or oonduit shall not be emaller then�'�-inch trade meters. A metal underground water Qipe shall be supplemented by an size and,where of iron or steel,shall have the outer atuface galvanized or additional electrode of a type specitied m Section 250-S1 or in Section 250- othecwise metal-ooated for conosion pmtecdon. 83. The supplemental electrode shall b� pernutled to be bonded to the (2� E��ctrales af rods of.iron or steel shall be at least�8 inch(15.87 mm) grounding electrode wnductor, the grounded service-enlrance conductor, ,� diameter. Stainless steel rods�less than�e inch (15.87 mm)'in diameter, the grounded service raceway,or any grounaed service enclosure. I�nonferrous rods,or their equivalent shall be listed and shall not be less than Wl�re the supplemental electrode is a made electrode as in Section 25U- �/Z�ch(12.7 mm)in diameter. ' 83(c)or(d),that portion of the bonding jumper that is the sole connection to the supplemental�rounding electrode shall not be required to be larger g 3) The electrode shall be installed such�that at least S feet(2.44 m�of than No.6 copper wue or No.4 aluminum wire. , len th is in contact with the soil. It s6all be dtiven to a depth of not ess than 8 feet (2.44 m) except that, where rack bottom is encountered, the Fxce,ption: 77:e supplen�ntnl elecmxfe slurJ!be pemri[ted to be boiided electrode shall be driven at an obGque angle not to eaceed 45 degrees from [o tlee ueterior me�al water prping ot any co�:venient point as covered p: the vertical or shall be buried in a trench that is at least 2�/Z feet(762 mm) Section 250-81, Ezreption No. 2. • I deep.The upper end of the electrode shall be flush with or belvw ground