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Grounding the Electrical System

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  1. Grounding the Electrical System Reference: AAVIM “Electrical Wiring” Created May 2007

  2. Purpose of the Grounding System • Fundamental to the safety of those installing, using, and servicing the electrical system • Assures the system will work properly while preventing damage to the system

  3. NEC Requirements • All electrical systems serving structure must be bonded together • Including the following • Electrical wiring system • Telephone system • Phone system • Burgular alarm system • Cable or satellite system

  4. Grounding • The process of making a planned, continuous, connection between NON-CURRENT CARRYING parts of the electrical wiring installation and the earth and some other conducting body

  5. Grounded • Describes the act of being connected to the earth or some other conduction body that serves in place of the earth

  6. Bonding • Process in which all NON-CURRENT CARRYING METALLIC parts of the electrical wiring system are permanently joined together to form a CONTINUOUS grounding path

  7. Bonding • Reduces the differences in potential between each electrical system • May be caused by power surges, lightning strikes or other types of ground fault type occurences

  8. Parts of the Electrical System • Circuits • Service Entrance Panel • Metal Water Pipe • Metal Gas pipe

  9. Materials in Grounding System • Must be approved by NEC

  10. The Grounding Electrode System • All materials must be grounded using approved bonding and grounding electrode systems • Check with local building code

  11. Metallic Pipe • Water pipe must always be bonded to the service entrance panel, grounding electrode conductor, or grounding electrode • Other metal pipe, such as gas pipe, which may become energized accidentally must be bonded to the electrical system grounded system

  12. Use of Bonding Jumper • To provide CONTINUOUS grounding path around devices such as water meters installed in metallic water pipe system

  13. Types of Grounding Electrodes

  14. Metal Underground Water Pipe • Must be bonded to the supplemental grounding system electrode and to the neutral bus bar in the SEP • Connection must be made within 5 feet of entering structure • Water pipe must be in direct contact with the earth for at least 10 feet

  15. Concrete Encased Electrode • Electrode encased in foundation footing covered with at least 2 inches of concrete • Electrodes must be at least 20 feet in length and consist of one or more ½” steel reinforcement bars

  16. Ground Ring • Bare Copper • At Least #2 AWG or larger • Encircling residence for a length of 20 feet • Buried at least 2 ½”

  17. Metal Framework

  18. Supplemental Electrodes • Typically made of metal rods, pipes, or plates

  19. Rod and Pipe Electrodes • Iron or steel rod electrodes • Must be 5/8” in diameter • Pipe must be ¾” in diameter • Galvanized or metal coated for corrosion resistance • 8 feet in length • Installed to a depth of 8” in direct contact with earth

  20. Nonferrous rods must be listed at no less than ½” • Stainless Steel- ½” diamter • Must be at or below ground level • Must be protected from physical damage

  21. Exceptions • If electrode can not be driven more than 4” into the earth b/c of rock or other obstruction • May be driven at an oblique and of no more than 45° from vertical • At least 8” of the electrode must be in contact with earth

  22. Multiple grounding rods • When more than one electrode grounding rod is used: • Must be installed not less than 6 feet apart • Must be bonded together with an approved bonding jumper to form single grounding electrode system

  23. Plate Electrode • May be used in areas where it is not possible to use a grounding rod or ring • Steel/Iron Plate electrode must be ¼” thick • Non-ferrous metal plate must be 0.06” thick • 2 feet square • Buried at least 2 1/2’

  24. Grounding Electrode Conductor • NEC permits • Copper • Aluminium • Copper-clad AL and AL-CU may not be used in contact with masonry, corrosive, or in direct contact with the earth