Newly Installed Outlet Trips the GFCI Immediately When Reset: Commissioning Fault Decision Tree
Why this matters
A GFCI that trips the instant you press Reset is not malfunctioning - it is detecting a real ground fault or wiring error introduced during installation. Ignoring or repeatedly resetting a persistent trip is a safety violation. The diagnostic sequence below isolates the cause in four steps so the wiring problem can be corrected at the source rather than masked.
GFCI devices protect against ground faults that can cause electrocution. Never bypass or tape over a repeatedly tripping GFCI. A GFCI that trips every time it is reset is detecting a real fault until proven otherwise by isolation testing. De-energize the circuit at the breaker before opening any connection.
Step 1 - Establish whether the trip is immediate or load-triggered
This single observation narrows the cause significantly.
Trip occurs the moment you press Reset, before any device is plugged in. The fault is in the wiring at or upstream of the GFCI device. The outlet itself is not the cause - the circuit has a wiring error or damage. Proceed to Step 2.
GFCI resets and holds, then trips only when a device is plugged in. The fault is in the device being plugged in, or in the load-side wiring run if there are additional outlets downstream of this GFCI. Test with a known-good lamp or phone charger before continuing. If the fault only appears with a specific device, that device is defective - not the installation. If the GFCI trips with any device, the load-side wiring is at fault. Proceed to Step 3, skipping to the load-side isolation sub-step.
Step 2 - Check line and load wiring assignment (most common cause)
Turn off the breaker for this circuit. Remove the GFCI outlet from the box so the wire connections are visible.
GFCI outlets have two sets of terminals, clearly labeled. One set is marked LINE and one set is marked LOAD. The terminals may also be color-coded or covered with a protective tab on the LOAD side at the factory.
The feed wires coming in from the panel must connect to the LINE terminals. The hot wire (typically black) goes to LINE hot; the neutral wire (typically white) goes to LINE neutral.
If the black and white wires from the supply side are connected to the LOAD terminals instead of the LINE terminals, the GFCI will trip instantly on reset. This is the single most common new-installation error on GFCI outlets.
Reverse the connections so supply feed is on LINE. Cap or leave unused any LOAD terminals if there are no downstream outlets on this run. Restore power and test Reset.
If the assignment was correct, continue to Step 3.
Step 3 - Isolate the fault to device wiring versus circuit wiring
With the breaker off, disconnect all wires from the LOAD terminals of the GFCI (if any downstream outlets exist). Restore power. Press Reset.
- If the GFCI now holds after Reset with nothing connected to LOAD, the fault is in the downstream wiring run or one of the downstream outlets. Reconnect the load-side run one outlet at a time to isolate which box contains the fault.
- If the GFCI still trips immediately with nothing on LOAD, the fault is in the supply-side wiring or in the GFCI device itself. Continue to Step 4.
Step 4 - Check for wiring damage and test the GFCI device
Check for a wiring nick or staple damage in the new run. If new wire was routed through walls or floors and secured with staples, a staple driven too tightly can cut through the insulation and create direct contact between the hot conductor and ground. Inspect every staple point along the new cable run. The staple should be snug but not compressing the cable jacket - no visible damage to the outer jacket at any staple location. If a staple damage point is found, that section of cable must be replaced; a nick in NM cable insulation cannot be reliably repaired in place.
Check for a shared neutral. If the new outlet was wired by tapping into an existing neutral conductor that also serves a different circuit, the GFCI will trip because current is returning on a neutral path it does not recognize as its own. Each GFCI outlet must have its hot and neutral matched to the same circuit. Verify with a non-contact tester that the neutral in the box belongs to the same cable as the hot wire being connected.
Test the GFCI device itself. GFCI outlets can fail internally, particularly if they were connected to power while incorrectly wired and then corrected. Swap the suspect GFCI with a new unit from stock. A defective GFCI that trips every reset is a rare but valid cause after ruling out all wiring faults.
If no wiring fault is found and the replacement GFCI also trips: the circuit has a ground fault elsewhere on the run that existed before this outlet was added. This is pre-existing and outside the scope of the new installation. Document the finding and advise the customer that a licensed electrician should perform a full circuit isolation to locate the pre-existing fault.
References
- NFPA 70 (National Electrical Code) Article 210.8 - Ground-Fault Circuit-Interrupter Protection for Personnel
- UL 943 - Standard for Ground-Fault Circuit-Interrupters (device performance standard)
- OSHA 29 CFR 1926.404 - Wiring Design and Protection (GFCI requirements in construction)
- IAEI (International Association of Electrical Inspectors) - Field Guide to GFCI Installation and Testing