Grounding the Electrical System

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Grounding the Electrical System

• Reference AAVIM
• Electrical Wiring
• Created May 2007

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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

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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

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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

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Grounded

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

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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

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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

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Parts of the Electrical System

• Circuits
• Service Entrance Panel
• Metal Water Pipe
• Metal Gas pipe

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Materials in Grounding System

• Must be approved by NEC

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The Grounding Electrode System

• All materials must be grounded using approved
  bonding and grounding electrode systems
• Check with local building code

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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

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Use of Bonding Jumper

• To provide CONTINUOUS grounding path around
  devices such as water meters installed in
  metallic water pipe system

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Types of Grounding Electrodes
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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

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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

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Ground Ring

• Bare Copper
• At Least 2 AWG or larger
• Encircling residence for a length of 20 feet
• Buried at least 2 ½

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Metal Framework
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Supplemental Electrodes

• Typically made of metal rods, pipes, or plates

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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

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• 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

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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

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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

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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

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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