SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hamg-g0b05

What condition makes a ground fault circuit interrupter (GFCI) disconnect AC power?

Current from a hot wire directly to ground.

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  1. Current from a hot wire to the neutral wire
  2. Overvoltage on the hot wires
  3. Current from a hot wire directly to ground ✔

Why: A GFCI watches for current leaking from a hot wire straight to ground. When it detects that leak, it cuts the power.

Huh, didn't know that: Only the hot wires in a four-conductor 240 VAC circuit should be attached to fuses or circuit breakers.

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A GFCI has one rule: if the current takes a shortcut, the power takes a break.
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References

Answer: Current from a hot wire directly to ground. A GFCI watches for current leaking from a hot wire straight to ground. When it detects that leak, it cuts the power.

  1. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    Which of the following conditions will cause a ground fault circuit interrupter (GFCI) to disconnect AC power?
    Checked 2026-10-11.
  2. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    B. Current flowing from one or more of the hot wires directly to ground
    Checked 2026-10-11.
  3. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    Which wire or wires in a four-conductor 240 VAC circuit should be attached to fuses or circuit breakers?
    Checked 2026-10-11.
  4. NCVEC 2023-2027 General Class Pool and Syllabus (6th Errata, Feb 4 2026) ncvec.org/downloads/General%20Class%20Pool%20and%20Syllabus%202023-2027%20Public%20Release%20with%206th%20Errata%20Feb%204%202026.pdf
    A. Only the hot wires
    Checked 2026-10-11.

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