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Grounding versus Bonding

PART III. GROUNDING ELECTRODE SYSTEM AND GROUNDING ELECTRODE CONDUCTOR

Sections

250.50 Grounding Electrode System.

All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present at each building or structure must be bonded together to form the grounding electrode (earthing) system. Figure 250–91

  • Underground metal water pipe [250.52(A)(1)]
  • Metal frame of the building or structure [250.52(A)(2)]
  • Concrete-encased steel [250.52(A)(3)]
  • Ground ring [250.52(A)(4)]
  • Ground rod [250.52(A)(5)]
  • Grounding plate [250.52(A)(6)]
Exception: Concrete-encased electrodes are not required for existing buildings or structures where the conductive steel reinforcing bars aren’t accessible without disturbing the concrete.

Where an underground metal water pipe electrode, metal building or structure frame electrode, or concrete-encased electrode is not present, one or more of the following electrodes specified in 250.52(A)(4) through (A)(7) must be installed to create the grounding electrode (earthing) system. Figure 250–92
  • Ground rod [250.52(A)(5)]
  • Grounding plate [250.52(A)(6)]
  • Metal underground systems [250.52(A)(7)]


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