A GFCI (ground fault circuit interrupter) outlet is a special type of outlet designed to protect against electric shock. When a GFCI detects a difference in electric current flow between the hot and neutral conductors, it will quickly shut off power to prevent harm. However, sometimes a GFCI outlet may trip for what seems like no reason at all, refusing to allow anything to be plugged in. There are several potential causes for a GFCI outlet not allowing devices to be plugged in.
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Moisture
One of the most common reasons a GFCI outlet won’t allow devices to be plugged in is moisture. GFCIs are very sensitive to moisture and even high humidity can cause nuisance tripping. Sources of moisture that can trip a GFCI include:
- Condensation – If the GFCI outlet is on an exterior wall that gets cold, condensation can form inside the outlet when warm moist air comes into contact with the cold surface.
- Leaks – Leaky plumbing, roof leaks, or other water intrusions can cause moisture to get into a GFCI outlet and trip it.
- Flooding – If flooding occurred and water got into the GFCI outlet, even after drying out it may still trip.
- Damp locations – Bathrooms, basements, crawl spaces, and other damp locations can cause nuisance GFCI tripping.
- High humidity – Humid summer weather or rainy seasons can contribute to moisture in the air that leads to tripping.
If moisture is suspected, thoroughly dry out the outlet location. Repair any leaks or sources of dampness. If the problem persists, the GFCI may need to be replaced.
Old age
Like any electrical component, GFCI outlets can wear out over time. GFCIs installed in the 1970s-1990s were required to last about 10 years. Newer GFCIs are designed for a 20+ year lifespan. If your GFCI outlet is more than 10-15 years old, its internal components may simply be wearing out causing nuisance tripping. Replacing older GFCI outlets is recommended.
Loose wiring
Electrical connections can become loose over time due to expansion/contraction with temperature changes, vibrations, wire creep, etc. If the hot and neutral wires inside the GFCI outlet box become slightly loose, it can cause a small difference in current flow that trips the GFCI. Tightening the wiring connections at the GFCI usually fixes this problem. Turn off power before removing the outlet to check wiring.
Faulty appliance
Sometimes the problem is with an appliance plugged into the GFCI rather than the GFCI itself. If an appliance has any kind of short circuit, ground fault, or damaged power cord, it can cause the GFCI to trip. Try plugging in appliances one at a time to find the faulty one. Or test appliances by plugging into a normal outlet to see if they trip a breaker. Any damaged or faulty appliance should be repaired or replaced.
GFCI failure
Like any electrical part, GFCIs can also simply fail or become defective over time. If the GFCI outlet trips repeatedly for no apparent reason and nothing else fixes the problem, the GFCI itself is likely bad and should be replaced. A damaged GFCI will be unable to provide proper shock protection.
Incorrect wiring
Mistakes made when wiring a new GFCI outlet can lead to nuisance tripping. Common wiring errors include connecting the hot and neutral wires incorrectly, using the wrong wire gauge, loose connections, or grounding issues. Hire an electrician to evaluate wiring if you suspect the GFCI wasn’t installed properly. Never try to override or bypass a tripped GFCI.
In older homes, the neutral wire is sometimes shared between multiple outlets. This is no longer allowed by electrical code. When outlets share a neutral wire, it can lead to overloading and cause GFCIs to trip when many devices are plugged in. An electrician can determine if shared neutrals are the issue and rewire the outlets.
Nearby motors or appliances
Large electric motors, such as those in refrigerators, washing machines, or air conditioners, can sometimes create “electrical noise” that interferes with GFCIs due to their heavy power draw. If the GFCI trips only when starting certain motors, consider plugging those appliances into a different outlet farther away on a different circuit.
Line vs load miswire
GFCI outlets have LINE terminals that connect to the incoming power source, and LOAD terminals that send power out to other outlets downstream. If these ever get flipped around, the GFCI will not reset properly. An electrician can correct a line vs load miswire.
Testing procedure
To properly diagnose a GFCI outlet issue, follow these steps:
- Unplug everything from the outlet.
- Press the “Reset” button to try resetting the GFCI.
- If it doesn’t reset, try pressing the TEST button. This should trip the GFCI.
- Press Reset again. If it still won’t reset, the GFCI may be damaged and need replacement.
- Plug in just one appliance/device and see if it trips the GFCI. Repeat for other devices.
- Check for moisture or signs of water leaks near the GFCI.
- Inspect all appliances for damage before plugging into the outlet.
- Have an electrician evaluate the GFCI wiring if moisture/appliances are not the issue.
Following these steps will isolate whether the problem is due to an appliance, moisture, or the GFCI itself. Call an electrician if you determine the GFCI is defective or incorrectly wired. Never try to override a tripped GFCI, as this poses a shock hazard. A properly functioning GFCI outlet is critical for preventing electrocution.
GFCI vs AFCI
It’s important not to confuse GFCI outlets with AFCI outlets. AFCIs (arc fault circuit interrupters) are designed to prevent electrical fires by detecting dangerous arcs or sparks in the wiring. However, AFCIs do NOT protect against electric shocks like GFCIs do. Make sure you are using the correct outlet for the required type of protection. Bathrooms, kitchens, basements and other damp locations need GFCIs, while AFCIs are more common in bedrooms and living areas.
GFCI breaker vs outlet
GFCI protection can also be provided at the circuit breaker panel with a GFCI breaker. This protects the entire circuit. GFCI outlets provide protection just at the outlet location. If you have a GFCI breaker, make sure outlets are labeled “GFCI Protected” so you know they are covered. You do not need GFCI outlets if you have a GFCI breaker.
Conclusion
Nuisance tripping of GFCI outlets usually comes down to moisture, an old/damaged GFCI, or a faulty appliance. By methodically testing appliances, checking for wiring issues, and addressing moisture problems, you can determine the cause and correct it. Faulty GFCIs should always be replaced immediately since they can no longer provide shock protection if they are unable to reset properly or trip when needed. Contact a qualified electrician if you cannot get your GFCI outlet to function normally after troubleshooting.