If you’re unsure how to test a GFCI outlet, this guide gives you all the detail you will need.
You should test a GFCI (Ground Fault Circuit Interrupter) outlet when there is a problem because it can only operate normally to protect you if it works properly.
The GFCI outlet has two buttons, ‘Reset’ and ‘Test.’ You can press these to reset and test the outlet, respectively. You can also use an instrument to test a GFCI, such as a GFCI outlet tester, a voltage or current tester, and a multimeter. Besides testing for power, you might also have to deal with a problem, such as frequent tripping and testing multiple locations if other outlets are connected to the same GFCI.
GFCI outlets with three wires provide additional protection compared to regular power outlets.
They can protect against electrical shock if a faulty appliance is plugged in. They do this by sensing minor changes in current flow and shutting the power off in a fraction of a second (~1/40). For instance, if you inadvertently drop a hairdryer into the water, the GFCI will detect the current interruption and instantly cut the power to the outlet, thus preventing the person from touching it and getting electrocuted. It can also detect a power or current surge or imbalance in power quicker than a circuit breaker.
This safety aspect makes GFCI outlets ideal for kitchens, bathrooms, and outdoor areas. However, I recommend you use GFCI outlets throughout your home, or at least in the most hazardous areas. The only drawbacks are that they are larger than regular outlets and more expensive. But for the safety advantage, they are worth using.
When Should You Test a GFCI Outlet?
You should test a GFCI outlet whenever you notice something unusual, suggesting that there might be a fault with the outlet.
This might happen, for instance, when you have overloaded a circuit or when water or moisture enters an outlet.
Faulty wiring can also cause a problem. A ‘ground fault’ occurs if the current rogue heads toward the ground.
Apart from testing when there is a mishap, you should also check all the power outlets in your home as a general routine, perhaps annually or semi-annually, or during a major renovation.
Testing a GFCI Outlet
To test a GFCI’s ability to power on and off, press the ‘test’ button with an appliance plugged in (or without one).
It’s the bottom button in the GFCI outlet below. It may be uncolored or in black, but it should also be marked ‘Test.’
When you press it, you may hear a snap sound, and the power should shut off. If it does, then the GFCI outlet is operating as it should to give you the extra protection for which it is designed.
If no appliance was attached while testing the power, you can do so now and confirm that there is no power. Alternatively, you can insert a current/voltage tester to confirm. Neither should turn on. If the GFCI outlet has a light indicator, it will turn off, as shown in the pictures below (small green light at the bottom right of the outlet).
GFCI testing I
The power should be off after pushing the test button.
Push the reset button.
The power should turn on after pushing the reset button.
If the button trips again as soon as you press it or shortly afterward, then it indicates that there might be a dangerous current in the circuit.
If the button doesn’t pop out when pressed, there might be no power coming to it, or else the GFCI might be bad.
In either of these cases, you will need to investigate the problem further or call an electrician.
GFCI Outlet Testing Tools
Special testing instruments are available for testing a GFCI outlet.
Using a GFCI Outlet Tester
One such instrument is the GFCI outlet tester, also called a GFCI receptacle tester.
It is a simple electrical device with LED light indicators. Advanced models might also have a display. A GFCI tester can check whether an outlet has been wired correctly. It is useful because it identifies common wiring problems, including open hot, neutral, or ground, reverse polarity, and reversed hot or ground.
To use a GFCI tester, plug it into the outlet and note the indicator lights.
The test button on a GFCI tester works similarly to the ‘Test’ button on the GFCI outlet itself. Press it to test the safety feature, i.e., the outlet can power off if a problem occurs.
The GFCI is a very useful device. If you have a lot of GFCI outlets in your home, I recommend having a GFCI tester. It is not expensive. Furthermore, some features can also be used to test non-GFCI outlets.
Using a Non-Contact Voltage Tester
Another instrument you can use to test a GFCI outlet is a non-contact voltage (or current) tester.
It is easy to use. Simply bring it close to a potential source of electricity. If current is present, it will light up. It is safe to use because there is no contact involved. However, you can also use a normal contact tester.
In the model pictured below, the tester gives visual and audible indications. The light flashes and/or beeps to indicate that there is a current.
Using a Multimeter
You can also use a multimeter to test a GFCI outlet.
As with a regular voltage tester, you can use a multimeter to test the voltage or current levels. However, a multimeter will give you an accurate reading, making it more informative.
Simply set the multimeter to an appropriate range for what you want to measure. For example, to measure AC voltage, ensure the selected range covers up to 120 volts.
Be careful when using a multimeter: Don’t touch the metal prongs while testing.
Testing a GFCI Outlet for Other Issues
Testing for Power
If you need to test the new GFCI outlet, you can do that either by:
- Inserting a plug into the outlet to see if it turns on, or
- Inserting a tester into the hot (short vertical) slot.
I covered these above.
If it keeps tripping too frequently, the circuit might be overloaded. If it trips when nothing is plugged in, it isn’t very accurate and must be replaced.
If you suspect the GFCI outlet is not working as it should, open it and ensure the wires are connected properly.
If you use a single GFCI to serve multiple outlets, don’t automatically assume the source of the problem is the GFCI outlet.
Some homeowners save money connecting ordinary (non-GFCI) outlets to a single GFCI outlet. Under this arrangement, a current leak or surge in connected outlets will cause the GFCI outlet to power off. Therefore, in the event of a problem, you must check all the connected outlets until you find the one to fix it.
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