Installing GFCI in garage with no ground


I have a rehab house I just sold. The HI suggested installing GFCI’s for outlets. Makes sense, I would make the same recommendation.

The feed from the house to the garage is a 12-2 wire no ground. From the feed at the garage junction box, the garage circuit is a 12-2 with ground. What is the correct way to effectively GFCI the outlets in the garage. Now I know I can trick it by connecting the ground t the neutral, but I know that is wrong.



You don’t need the ground wire for a safe GFCI installation. The trip sensor simply runs off of the neutral side. When a change of current is sensed on the neutral side, the GFCI trips.

No ground needed, but the GFCI should be clearly labled “No Equipment Ground”.

Where you have the ground wire at the garage side, simply bond the ground to the box and wire the receptacle accordingly.


Thanks, Plastic boxes are used. The GFCI did not trip. When I tested Outlet, it showed reversed polarity, although I am pretty sure it was wired correctly. I guess I need to re-check it


Two items…

  1. If you’re getting a reversed polarity reading on your tester, then it needs to be corrected. The black wire (hot) goes to the brass screw and the white wire (neutral) goes on the silver screw. This needs to be corrected, period.

  2. GFCI with “No Ground” will not trip with a tester. Simply press the test button on the outlet and it should trip. If not, it needs replacing.


When I test the outlet it is good, but when I hit the trip button to test the GFCI, it shows reversed polarity and does not trip the GFCI

If you’re using that cheap 3-light tester and you’re getting reversed polarity lights, then the wires are reversed and need to be corrected. This will not trip the GFCI with your tester nor manually.

If the outlet is ungrounded and wired properly, your tester will read ungrounded outlet. (I believe it’s the middle yellow light). This (also) will not trip the GFCI with the tester but will trip manually.

You need the ground connected in order to trip with your tester.


A 3 light plug-in tester will not trip a GFI without a ground wire. Without a ground wire you can only test by using the built-in test button on the receptacle.

Ok, now it makes sense. So long as the hot and neutrals are correct, the only way to test is manually. Thanks for all the input

[A GFCI receptacle, new or old, can’t trip with a plug in tester unless there is an EGC connected to the GFCI. There is no path for the test current to flow on without an EGC. When testing GFCIs with the internal test button, you must test for voltage on the GFCI receptacle after you push the test button. A GFCI receptacle that has the power connected to the load terminals will still have power( on older models) on the receptacle even when the button shows that the device has tripped.

The GFCI works because it detects the difference between the grounded and ungrounded conductor.

GFCI is a Ground Fault Circuit Interrupter. The Ground Fault Interrupter is a receptacle that has the ability to open or disconnect the power from the output of the receptacle. The Ground Fault Circuit Interrupter is a breaker that has the ability to disconnect the power from a circuit. The ground fault senses a difference in the flow of current from the hot wire through the neutral, if that difference is about 5 milliamps or more the ground fault will trip the circuit out. It actually assumes that if the current is not flowing in the neutral it is flowing through something else. Some motor windings have sufficient losses to cause one to trip out so don’t use a GFCI circuit for a refrigerator or washer outlet. You should use (and the NEC requires) the use of GFCI protected outlets within 6 feet of a sink, anywhere in a bathroom, in a garage or outside; anywhere an outlet can be reached from a water source, a wet area, or earth ground, you should use GFCI protection. A GFCI receptacle has a line side (incoming power) and a load side (outgoing power). The receptacle will not work if the incoming power is connected to the load side of the receptacle. Connect the incoming power to the line marked terminals and the continuation of the circuit (the next outlet) to the load terminals. The one GFCI will protect all the following plugs or receptacles connected in this way. Even if you don’t have a continuation of the circuit, connect the power to the line side of the receptacle. GFCI receptacles and GFCI breakers have a test button that should cause the circuit to trip, operate the test button after installing and regularly there after to be sure it works properly.]

Found this on this MB – Lord knows how long ago…kinda like it…


**Inside each GFCI receptacle is a little man with a test meter. He also has a bed, a small kitchenette, a TV with satellite service, and books to read. When you are running something on a GFCI outlet he gets out of his chair, grabs the meter, and makes sure that 100% of the current coming into the receptacle on the black wire is going back out the white wire. If the white wire is missing any current at all he kicks this foot pedal that makes the GFCI pop. **

**Sometimes he notices that you are using a device that draws too much current. He can tell, because the wires are getting too warm. **
"Not my problem", he says, "Union rules. This one gets handled by the over-current protection guys."

Makes perfect sense:)

Must be an echo in this forum…

lol…always is…

No one can test a GFCI device with one to those plug-in testers period.

Yes it might trip the device and let you know that is on a circuit protected by a GFCI device but it DOES NOT test the device.

If you are using one of the testers and stating that a circuit is GFCI protected just because it tripped using the plug-in tester then STOP immediately.

The ONLY way to test a GFCI device for proper function is to use the trip button on the device.

OK, out with it!
Where did you come up with this?
I need to go sue someone for my three light testers that I have used all these years.

That can “trick” you into an electrical hazard! It’s not just wrong.

OK, Why are selling Them? Please explain

I disagree…When you are pressing the black trip button on the cheap 3-light testers, they are still placing a small load between the Load side HOT and the equipment grounding conductor. I’ll always test the GFCI’s with my cheap 3-light tester until someone can prove me wrong.

The .gov site tells the public…

To test a GFCI…

  • Plug a nightlight into the outlet and turn it on.
  • Press the “TEST” button on the GFCI outlet. Did the light go out? If not, replace the GFCI.
    *]Press the “RESET” button. Did the light come back on? If not, replace the GFCI.

I agree with David.

I test with both , as I have read that either will do the job.
It is simply easier to trip with a three light tester once you have it in place checking for current.
Not a big issue.