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NEC Article 250 Lookup Practice (California Electrician Exam)

Article 250 is long, and candidates lose minutes wandering it. The fix is a map: know which section and table answers a grounding question before you open the book.

Last reviewed June 2026

What to train

  • The split between the electrode conductor (250.66, off the service) and the equipment ground (250.122, off the breaker).
  • Reading Table 250.66 by the largest ungrounded service conductor.
  • Reading Table 250.122 by the overcurrent device rating.
  • Where bonding lives: 250.102 jumpers, 250.104 water pipe and building steel.

What slows candidates down

  • Confusing the two tables and sizing the equipment ground off the service conductor.
  • Searching 'ground wire' instead of the defined terms in the index.
  • Reading Article 250 from the top instead of jumping to the Part you need.
  • Missing that the main bonding jumper has its own section.

Mini drill: find it fast

Close the book. Read each cue, say the index keyword you would search and the article out loud, then check yourself. If it takes more than fifteen seconds, that one goes on your tab list.

  • Size the grounding electrode conductor

    Sized by the largest service-entrance conductor.

    Keyword: Grounding electrode conductor

    Table 250.66

  • Size the equipment grounding conductor

    Sized by the overcurrent device ahead of it.

    Keyword: Equipment grounding conductor

    Table 250.122

  • Supply-side bonding jumper

    Sized from Table 250.102(C)(1).

    Keyword: Bonding jumper, supply-side

    250.102(C)

  • Ground rod electrode requirement

    Rod electrodes and their installation.

    Keyword: Grounding electrode, rod

    250.52 and 250.53

  • Main bonding jumper at the service

    Ties the neutral to the enclosure at the service.

    Keyword: Bonding jumper, main

    250.28

Train this against the clock

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