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NEC ARTICLE 250/ANSI/TIA/EIA 607C: GROUNDING AND BONDINGArticle 250 of the National Electric Code is the most extensive article in all of the code. The reasons for the extensive coverage of grounding and bonding are because these two practices are responsible for the correct operation of all overcurrent protective devices in a building; they bring all metal enclosures to an equal potential; they insure a safe path for voltage surges caused by lightning or other transients to ground; and they provide a consistent reference for technical equipment that is forced to operate in difficult electrical environments.This 4 hour course will be a review of Article 250 in the 2017 National Electric Code and TIA/EIA 607C concentrating on how bonding and grounding are different and serve different purposes; how bonding back to the electrical source guarantees the safe operation of overcurrent protective devices; how grounding while in most cases is a necessity for the safe dissipation of high voltage surges is not an effective ground-fault current path; how bonding insures correct transmission of telecommunications; and how different systems of various voltages must comply with the code. It is important that both agencies (NEC and ANSI/TIA) require the same single building ground for both safety and performance.One of the most important requirements of Article 250 is under the general requirements for Grounding and Bonding in 250.4 (A) (5) which includes the definition of an Effective Ground-Fault Current Path. The absolute “shall” is in the final line: “The earth shall NOT be considered as an effective ground-fault current path.” While the NFPA recommends a ground resistance of 5 ohms or fewer and the IEEE and Telecommunications Industry have made the same recommendation (ANSI/TIA/EIA 607C), Article 250 makes reference in 250.52 (A) 2 that “a resistance to earth of 25 ohms” is acceptable for a grounding electrode and auxiliary electrodes. That statement is a very good place to start a discussion of grounding and bonding.COURSE OUTLINEScope of the Articles (250.1/ANSI/TIA 607C) [30 Minutes]A review of the articles to show both the reason for the code requirements and the mechanical means to comply.Code Change (Clarification)<50 volts not required to be grounded and bonded unless derived from a 277/480 volt source or is on an ungrounded system. Warning label language and material specified.Definitions (250.2) [20 Minutes]This article has multiple terms that must be understood. A list will be provided and each term explained. (Lists Attached)QUIZ (Quizzes break up the class and provide a review.) [5 Minutes]General Requirements (250.40) [15 Minutes]Separately Derived SystemsCode Change (Clarification)Generators are not necessarily separately derived systems if the neutral is unswitched and directly wired to the building disconnect or main.Grounded and Ungrounded SystemsOvervoltage SourcesTelecommunications Industry of America/Electronics Industry of America and their grounding and bonding methods under 607C [30 Minutes]Category Cables4 balanced twisted pairs, twist (pitch) varies to reduce AXTDigital Signal processing/ Full Duplex5e 24awg, 100 MHz, 6a 23awg, 500 MHz, 8 40GBs HEVC (High efficiency video coding), H265 compressionHD Base T, stream without forward error correctionsDoes not connect to patch panelCarries power (100 watts) PSE, PD Fiber vs. CopperUbiquitous RJ45 connectorsInstalled Copper BaseCostPower Requirements of IoT, Devices, LightingDefinition ChangesTelecommunications Main Grounding Busbar/ Primary Bonding BusbarTelecommunications Grounding Busbar/ Secondary Bonding BusbarGrounding Equalizer/ Bonding Backbone ConductorTelecommunications Grounding Backbone/ Telecommunications Bonding Backbone ( 6 awg-750 mcm)QUIZ [5 minutes]Objectionable Current (250.6) [15 Minutes]Neutral/Ground ProblemConnection Methods (250.8—12) [15 Minutes]Review of Mechanical Devices with samplesQUIZ [5 Minutes]BREAK [10 Minutes]System Grounding (250.20—30) [10 Minutes]Grounding of sources as opposed to equipment.Ungrounded/Grounded SystemsCode Change: 250.24Single phase or Three phase systems either “Wye” or High Leg Delta connected using the neutral as a circuit conductor must be grounded and bonded and the neutral must be sized according to 250.24 (C) or 250.102 (C) (1)The neutral (grounded) conductor now must be sized according to 250.24) and 250.102 (C) (1) to carry not only the unbalanced current but also the short circuit current of the ungrounded conductors. The structural steel and water pipe system is no longer the recommended grounding electrode conductor. The text is simplified to allow for multiple methods. The size of busbar for connecting grounding electrodes is clarified to ?” x 2” and as long as necessary.Grounding Electrode Systems (250.50—53) [20 Minutes]Code Changes250.52 specifies that structural steel is a good grounding electrode conductor even if it is not a good grounding electrode (not ten feet in contact with the earth).250.53 specifies the requirements of grounding electrodes:If practicable, pipe electrodes must be embedded below the permanent moisture level and be free from nonconductive coatings (e.g., paint or enamel) [250.53(A)(1)].A rod electrode must be supplemented by an additional electrode that’s bonded to the service disconnect or one of the other four items listed in 250.53(A)(2).The supplemental electrode for a rod electrode must be installed at least 6 ft from the rod electrode [250.53(A)(3)].Electrodes for premises systems must be at least 6 ft from lightning protection system grounding electrodes [250.53(B)].Two or more grounding electrodes bonded together are considered a single grounding electrode system.The bonding connection for the interior metal water piping system, as required by 250.104(A), can’t depend on equipment likely to be disconnected for repairs or replacement. Install a bonding jumper around insulated joints and equipment likely to be disconnected for repairs or replacement [250.53(D)].When an underground metal water pipe grounding electrode is present, it must be used as part of the grounding electrode system [250.52(A)(1)].Rod electrodes must be installed with at least 8 ft of length in contact with the soil. If rock bottom is encountered, the rod must be driven at an angle not to exceed 45 degrees from vertical [250.53(G)].Lightning Protection Systems 250.60Code Change250.60 has changes in the Informational Notes 1 & 2 that require Lightning Protection Systems to be bonded to the building grounding electrode to eliminate voltage differentials. Installation of Grounding Electrode ConductorsCode Change250.64 (A-F) contain multiple changes in how Grounding Electrode Conductors are to be installed.250.68 (C) revises how water pipe, structural steel and rebar can be used as a Grounding Electrode Conductor. Water pipe must have its connection within 5’ of entering the building; structural steel represents a good grounding electrode conductor even if it can’t function as a grounding electrode; and rebar can’t be coated or painted or subject to corrosion.Bonding (250.90—98) [15 Minutes]All electrical conductive componentsClarify again distinction to GroundingBonding Conductors and Jumpers (250-102—106) [10 Minutes]Distribute ExamplesEquipment Grounding and Methods (250-110—148) [10 Minutes]Rods, piping, rings, plates, concrete encasement, etc.FINAL QUIZ [5 Minutes]DEFINITIONS (NEC/ANSI/TIA)GroundingBondingOverload, Short Circuit, Ground FaultEffective Ground-Fault Current PathObjectionable CurrentMain Bonding JumperSystem Bonding Jumper/ Supply Side Bonding JumperPrimary Bonding BusbarSecondary Bonding BusbarBonding Backbone ConductorTelecommunications Bonding Backbone ( 6 awg-750 mcm)Grounding Electrode Conductor / Grounding ElectrodeCOURSE OBJECTIVESClasses on Grounding and Bonding can take days if each part of 2017 NEC Article 250 or ANSI/TIA/EIA 607 C is examined completely. This course is designed to cover in four hours the basic understanding of each documents’ scope; insure a proper understanding of the terms used; clearly distinguish the purpose of grounding as opposed to bonding and how each method has a distinct role to play in the safe operation of electrical power; magnetic interference and the role of grounding and bonding in data and communications; and review the different kinds of mechanical connections in any properly designed grounded and bonded system.LEARNING OUTCOMEElectricians who take this class will understand clearly the difference between Grounding and Bonding. They will understand the scope and complexity of documents; they will be able to explain why the 2017 NEC prohibits grounding as an effective ground fault current path; they will be able to define the important terms in the two documents; they will be aware of how lightning and transients affect electrical systems; they will understand the importance of an effective ground fault current path in a bonded system; they will become familiar with the performance requirements of ANSI/TIA 607C; and they will gain some familiarity with the different mechanical grounding and bonding methods.INSTRUCTORThe course instructor is Ralph Bliquez who teaches at the NECA/IBEW Training Center and is authorized to teach continuing education classes for credit by the states of Oregon, Washington, California, Nevada, Montana and Utah.COURSE MATERIALSThe materials for the course will be a selection of slides with quotations taken directly from Article 250 of the 2017 NEC, examples of the different jumpers and ground connections both in slides and physical examples, illustrations of the correct and incorrect methods of bonding and grounding per the Article, a review of TIA/EIA 607C and their grounding and bonding recommendations for data and communications, sources of Objectionable Current and its effects on electromagnetic interference and the four quizzes which reinforce the material. ................
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