How To Test A GFCI Breaker With a Multimeter
A Ground Fault Circuit Interrupter (GFCI) is a protective electrical outlet with a breaker that cuts off the power supply to its sockets when there is a leak within its circuit.
It helps protect against fatal electric shocks caused by poor grounding.
Are the buttons on your GFCI outlet acting weird? Do you suspect that the breaker has developed a fault?
Our guide presents you with all you need to know about how to test a GFCI breaker with a multimeter.
Let’s get right into it.
Tools Required To Test A GFCI Breaker
Testing a GFCI requires
- A multimeter,
- Protective Equipment
- Phillips Screwdriver
How To Test A GFCI Breaker With a Multimeter
To diagnose a GFCI breaker, push its test and reset buttons, test the voltage supply from its outlets with a multimeter, and finally open the outlet up to check the condition of its wiring and ground connection. If the GFCI breaker or outlet fails any of these tests, you should fix or replace it.
We would go deeper into what each of these testing stages connotes and how you may apply solutions to issues you find.
Step 1: Wear Protective Equipment
Our test on the GFCI involves multiple procedures where you deal with live current. To avoid fatal electrical hazards, you want to wear rubber insulated gloves and safety goggles.
Step 2: Push Test And Reset Buttons
The GFCI buttons play very specific and clear roles within the electrical outlet’s circuit. The test and reset buttons are usually placed between the two sockets on the GFCI outlet and are also clearly labeled.
You use the test button to check if the GFCI is still working, so you may determine if you can rely on the outlet or not.
On the other hand, you use the reset button to place the GFCI back in its active protective mode after it has been tripped.
In this first step, you hear a clicking sound when you push the test button, which means the breaker has tripped or cut off the connection.
You should also hear a click when you push the reset button, which indicates the GFCI is back in its active protective mode.
If you don’t hear a clicking sound in any of these tests, the GFCI may be bad and you should be wary of it.
The next step involves a multimeter and you may use it to further examine if the GFCI performs its function or not.
Step 3: Inspect Voltage Supply In Outlet
Remember that a good GFCI entirely cuts the power supply to the electrical outlets once it has been tripped.
The multimeter test helps you to check if the breaker performs this function, regardless of the result of the test and reset button trials.
Firstly, set your multimeter dial to measure AC voltage, and this is usually represented by “V~” or “VAC” on the meter.
You also place the multimeter in the lowest voltage range. On most multimeters, this is typically the 200VAC range, but it could be lower on yours.
Next, push the test button to trip the GFCI and mimic a grounding fault. Once this has been done, insert your multimeter leads into the outlet slots.
The shorter vertical slot is the hot slot, the long vertical slot is the neutral slot, and the semi-circle slot is the ground slot.
You insert your black negative multimeter probe into the neutral slot and then insert the red positive probe into the hot slot.
Now, it’s time for evaluations. Since the test button has been pushed and the circuit breaker is thought to be tripped, you don’t expect to get any value whatsoever from the multimeter.
A value of zero (0) from the multimeter tells you that the breaker is serving its purpose.
If you got a value other than zero, however, there is a fault with your GFCI outlet and it should be replaced.
Sometimes, this fault could be a circuit ground connection problem, and we will subsequently go into that.
Before this, however, we check the reset button and overall voltage supply.
To do this, push the button and your outlet is expected to have a voltage supply now.If your outlet uses a single-pole GFCI, you should get about 110V to 120V from it, while double-pole breakers work with 220V to 240V.
With the multimeter probes still in their previous positions (black probe in the neutral slot and red probe in the hot slot), check the multimeter for a reading.
If you don’t get a value within these ranges for your respective GFCI breaker class, then the entire GFCI outlet itself may be bad.
One factor causing this, however, could be incorrect wiring, and you may proceed to the next step.
Step 4: Check The Wiring In GFCI Outlet
Now, before you proceed further, you want to cut off the power supply to the entire GFCI connection from your home’s main electrical panel or fuse box.
This ensures the most safety, as we are now directly dealing with wires that carry a lot of current and voltage when live.
Once you have tuned off the power, you simply inspect where each outlet slot wire goes to.
As expected, there are two wires in your GFCI socket circuit; the line wire that goes to the hot outlet slot and the load wire that connects to the neutral outlet slot. You may check our guide on identifying line and load wires.
The line wire is typically black, while the load wire is white, and you look to see that these wires are connected to their appropriate slots.
A bad connection here could be why your GFCI outlet may be malfunctioning.
Once you have verified that the connection is right or once you have changed the connections to the appropriate setting, you then tighten the screws holding the wires in place. These wires may be making loose connections, which could be your problem.
Turn the power supply at your home’s electrical panel back on and check whether the GFCI outlet produces the right amount of voltage as expected during the multimeter voltage test.
Step 5: Inspect GFCI Ground
Finally, you want to check that the GFCI is properly grounded. This is a fairly easy task and requires the same procedure as testing voltage from the outlet slots.
For testing the ground connection, however, you leave the red probe in the hot slot and place the black probe in the semi-circle or “U”-shaped slot instead.
Once you do this, you expect to get a reading of zero volts when the breaker is tripped and about 110V if the power isn’t cut off.
The GFCI particularly helps to ensure your wall outlet circuit is properly grounded, so if it fails this test, then it doesn’t serve its purpose or guarantee your safety.
Any other reading in any of these checks means the breaker circuit has a faulty ground connection and should be fixed or replaced immediately.
We have an exhaustive guide on testing grounding within outlets, as well as how you may comprehensively test a 220V outlet for issues.
Testing a GFCI breaker in your home is a procedure you frequently want to engage in and not only when you notice problems with your electrical outlets.
This ensures that the appliances and important devices in your home are protected from electrical circuit shorts at all times.
Although checks through the external buttons may help you to make a very easy diagnosis, the multimeter is the right tool to accurately determine if your GFCI breaker is working or not.
It also helps with checking other devices and appliances in your home and automobiles.
How Do You Know If a GFCI Breaker Is Bad?
A GFCI breaker is bad if you don’t hear a click when you press the test or reset button, if there is an available voltage supply even when the breaker is tripped, or if it trips without any load.
How Often Do GFCI Breakers Go Bad?
Standard-quality GFCI breakers don’t go bad till after 10 to 15 years of using it, but this may be fast-tracked if the outlet is exposed to excessive moisture, chemicals, heat, or UV light.
Why Does GFCI Breaker Trip With No Load?
A GFCI breaker may trip without any load if there are loose, dirty, or defective connections or wires causing an overload or leak within the breaker. A bad GFCI breaker may also be the culprit.
Alex Klein is an electrical engineer with more than 15 years of expertise. He is the host of the Electro University YouTube channel, which has thousands of subscribers.