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HI Electrician: Safety, Grounding, Bonding, and Job-Site Practices

HI Electrician · Work through your exam, one topic at a time.

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Safety, Grounding, Bonding, and Job-Site Practices

This domain tests safe work practices and the grounding and bonding rules that make fault clearing possible. Expect questions on OSHA, NFPA 70E, lockout/tagout, temporary power, approach boundaries, grounding electrode systems, equipment grounding conductors, and bonding.

Shock, arc flash, and job-site controls

  • OSHA 1926 Subpart K covers construction electrical safety; 1910.147 covers lockout/tagout.
  • NFPA 70E defines shock approach boundaries, the arc flash boundary, PPE, and the energized work permit.
  • Test before touch with a properly rated meter; verify the meter on a known source.
  • Construction sites require GFCI protection or an assured equipment grounding conductor program under 1926.404.
  • De-energize, lock, tag, and verify before working.

Grounding and bonding

  • 250.4 requires a permanent, low-impedance fault path capable of carrying fault current.
  • 250.50 requires all grounding electrodes present to be bonded into one system.
  • 250.52 lists electrodes: rods, pipes, plates, concrete-encased, ring, and metal water pipe with at least 10 ft in contact with earth.
  • 250.66 sizes the grounding electrode conductor; 250.122 sizes the equipment grounding conductor.
  • 250.24 covers service neutral bonding; 250.30 covers separately derived systems; 250.32 covers separate buildings.
  • The neutral is the grounded conductor; the EGC is the grounding conductor; they are bonded only at the service or separately derived system.

Worked example

A 200 A service uses 2/0 copper service conductors. Table 250.66 requires a 4 AWG copper grounding electrode conductor. A 200 A feeder requires a 6 AWG copper equipment grounding conductor under Table 250.122. The reasoning: the GEC is sized from the service conductor size, while the EGC is sized from the overcurrent device rating. If the GEC is the sole connection to a rod, pipe, or plate electrode, 250.66(A) permits it not to be larger than 6 AWG copper.

Traps that cost marks

  • Bonding neutral to ground at a subpanel.
  • Using a ground rod as the only fault path instead of an EGC.
  • Undersizing the EGC or omitting bonding of metal piping.
  • Assuming conduit is an EGC without meeting 250.118.
  • Using a non-contact tester as the only verification.
  • Working energized without an energized work permit and correct PPE.