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Install a GFCI Outlet

How-to Guide Safety Updated Jun 19, 2026 · Electrical

Goal

Replace a standard receptacle with a GFCI (Ground Fault Circuit Interrupter) outlet, correctly wired so all downstream outlets on the circuit are also protected. Common job for kitchens, bathrooms, garages, basements, and outdoor receptacles per NEC Article 210.8.

Prerequisites

  • GFCI receptacle (15A or 20A - match the breaker)
  • Non-contact voltage tester + plug-in outlet tester
  • Standard screwdrivers (#2 Phillips, ¼" flat)
  • Wire strippers
  • Replacement cover plate if needed
  • 30 minutes per outlet

Verify the breaker amp rating matches the receptacle rating before starting. A 20A receptacle on a 15A circuit is fine; a 15A receptacle on a 20A circuit is a code violation.

Steps

  1. Identify the circuit. Plug a known-on lamp into the outlet, then trip breakers one by one until the lamp goes off. Map this on the panel schedule.
  2. Turn off the breaker. Verify dead with a non-contact voltage tester on both slots and screws. Test the tester on a known-live outlet first to confirm it's working.
  3. Remove the cover plate and the existing receptacle. Pull the receptacle out gently - old wires get brittle.
  4. Identify LINE vs LOAD. With the breaker still off, ask a helper to flip the breaker on briefly while you read voltage on each pair of wires with a multimeter. The pair reading 120 V is LINE (power coming in). Tape it. Turn breaker back off.
  5. Connect LINE wires to the LINE terminals on the GFCI (top pair on most models - read the label molded into the back of the receptacle).
  6. Connect LOAD wires to the LOAD terminals (bottom pair). LOAD-side wiring is what extends GFCI protection to downstream outlets. If there's only one cable in the box, leave the LOAD terminals empty and tape the LOAD slots over.
  7. Connect the bare ground wire to the green terminal.
  8. Push the receptacle into the box carefully - fold wires accordion-style, don't crush them. Secure with the long screws.
  9. Reinstall the cover plate.
  10. Restore power. Press TEST - the receptacle should click and disable. Press RESET - power restored. If TEST doesn't trip it, you've wired LINE to LOAD; swap them.
  11. Test every downstream outlet with the GFCI tester's "trip" button. They should all lose power when the GFCI trips and restore when you press RESET on the GFCI itself.

Verification

  • GFCI TEST button trips the outlet
  • RESET button restores power
  • Downstream outlets are protected (verified with tester)
  • Outlet tester shows correct wiring on all positions
  • No "open ground" or "reversed polarity" indicators

Troubleshooting

  • Won't reset, no power at all: LINE and LOAD are reversed. Swap them.
  • Resets but trips immediately under any load: actual fault somewhere on the circuit. Disconnect downstream loads one at a time to isolate.
  • Resets but a downstream outlet has no power: a wire on the LOAD side isn't terminated properly. Re-seat each LOAD-side connection.
  • Open ground on the tester: the bare wire isn't making contact with the green terminal. Tighten the screw or re-strip the wire.

Older homes may have wiring without an equipment grounding conductor. A GFCI is legal in this case (NEC 406.4(D)(2)(b)) but must be marked "No Equipment Ground" and "GFCI Protected" with the labels included in the receptacle package. Don't skip the labels - without them this is still a code violation.

References

  • NEC Article 210.8 (GFCI protection requirements by location)
  • NEC Article 406.4 (Receptacle replacement requirements)
  • Manufacturer installation instructions

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