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- l• ' . .._„_.. . . i _ , ,,,• i��.�j • ;''. . c"` - :r r� _ S 4^k 4 ARTICLE 250—OROUNDINQ � 70-127 70-128 NATIONAL EIECTRICAL CODE jumper shall be sized in accordance with Table 25U-95 usuig the rating of (b) Metel Freme of the Bullding. The metal frame of the building,where the circuit that may ener�ize the piping, effectively grounded. •�� The equipptent groundmg conductor for the circuit that may energize the �FpN)• Effectively grounded means intentionally aonnected to earth through a piping shall be permitted to.serve,as the bonding means. ground connection or connecdons of suBicienUy low impedance and having sutri- (FPN): Bonding all piping and metal air ducts within the premises will provide cient current�artying capecity to•prevent the buildup of voltages that mey tesult ln additional satety. , undue hazard to connected equipment or to person�. H.GrourMing Electrode System (c) Concrete-Encased Electrode. 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 mg of at leasf 20 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 steel reinforcing bars or rods of not made electrodes in accordance with Sections 250-8 (c) and (d), shall be less than �/Z inch (12.7 mm) diameter, or oonsisting of.at least 20 feet bonded together to form.the grounding electrode system. Interior metal l (6.1 m)of baze copper conductor 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) (iround Ring. A ground ring encircling the building or structure, in trodes and the grounding electrode oonductor.The bonding jumper shall be di�ed contact with the earth at a depth below earth surface not less than installed in aceordance with Sections 250-92(a) and (b), shall be sized in 2�2 feet(762 mm),consisting of at least 20 feet(6.1 m)of.bate copper con- accordance with Section �50-94, and shall be connected in tlie manner� ductor not smaller than No.2. specified in Section 250-115.The unspliced grounding electrode conductor shall be permitted to run to an}r convenient grounding electrode available 250-83• Made and.Other Electrodes. Where none of the electrodes spec- in the grounding eleCtrode system.It shall be sized for the largest ground- ifted in Section 250-81 is available,one or more of the electrades specifled ing electrode conductor tequtred among all the available electrodes. in(b)throu��d)below shall be used.Where practicable,made electrodes Exception No. 1: It shall be peimitted to splice the growuiing electrode shall be em e ded below permanent moisture level.Made electrodes shall co�uluctor by means of ir�ve�sible compression-type conr�ctors listed for be free f�om nonoonductive coatings,such as paint or enamel.Where more tlse prupose or the exother»uc we/ding process. �an 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 ExcepNon No. 2: In irulc�shial and coinn�e�ia!buildings whene coiuli- any other electrale of another grounding system. ' tions of»iaintenance 4nd supervision ensure that only qualifred persons will service the installa[ion and the entire length of the interior metal water ��N): 'Ibvo or more electrodes that are eHectively bonded together are to be pipe tfurt is being used for the conductor is e.xposed. treated as a single electiode system in this sense. ,,•; _ (FPN): See Section 547-5 for apecial grounding and bonding requ'vements for • �a) Metel Utiderg�ouDd Ges PIp111g Sy3t@m. A metal undergtound gas agncuitural buildings. piping system shall not be used as a grounding electrode. (a) Metai Underground Water Plpe. A metal underground water pipe in �b) Other Locel Metel Underground Syatems or SWcturee. Other local direct contact with the earth for 10 feet (3.05 m) or more mcludin an metal underground systems or sUuctures, such�es piping systems and metal well casing effectively bonded to the pipe) and electr�cally continu undergtound tanks. ous(or made electrically continuous b�bonding around insulating joints or (e) Rod and Plpe Eleetrodes. Rod and pipe electrodes shall not be less sections or insulating pipe).to the po�nts of connection of the grounding than 8 feet(2.44 m)in length and shall oonsist of the follrnving matetials, electrode conductor and the bonding canductors.Continuity of the ground- �d shall be installed in the following manner: ing path or the bonding connecdon to mterior piping shall not rely on water (1) Electrodes of pipe or conduit shall not be amaller than�'a-inch trade meters. A metal underground water Qipe shall be supp(emented by an size and,where of iron or steel,s6a11 have the outer surface gatvanized or additional electrode of a type specified m Section 250-81 or in Section 250- otheiwise metal-coated for corrosion protection. 83. The supplemental electrode shall b� pertnitted to be bonded to the (2) Electrodes of rods of.iron or steel shall be at least�e inch(15.87 mm) . grounding electrode conductor,the grounded service-entrance conductor, .� diameter. Stainless steel rods�less than�8 inch(15.87 mm)'in diameter, the grounded service raceway,or any grounc�ed service enclosure. I�nonferrous rods,or their equivalent shall be listed and shall not be less than Wt�re the supplementa!electrode is a made electrode as in Section 250- �/2�ch(12.7 mm)in diameter. • 83(c)or(d),that portion of the 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 larger �ength is in wntact with the soil. It shall be driven to a de th of not less than No.6 copper wue or No.4 alnminum wire. . P than 8 feet (2.44 m) except that, where rock bottom is encountered, the Exce,�tio��: TTie supp[emental elechmie s/ur/1 be pemtitted to be ba�ded electrode shall be driven at an obltque angle not to eaceed 45 degrees from to the uiterior metal water prping at a�ry co�:venient poui[as covered in t_he vertical or shall be buried in a trench that is at least 2�IZ feet(762 mm) Section 250-81, Excep[ion No. 2 • I deep. The upper end of the electrode shall be flush with or below ground