To test a GFCI receptacle

I am now studying for NHIE with 2000 practice questions.
But, I am really confused a question about testing a GFCI receptacle.
Actually, there are two questions for testing a GFCI receptacle with different answer

First one is
To test a GFCI receptacle, use _______________ .

  1. a GFCI testing device
  2. a multimeter
  3. an ohm meter
  4. the push button on the GFCI receptacle
    The answer here is 1)

Another is
The proper way for an inspector to test a GFCI receptacle is by ____________ .

  1. Pushing the test button
  2. Using a GFCI testing device
  3. Using a multimeter
    The answer here is 1)

I think two questions look same but they have different answer.

Which one is correct?

Push the test button is the correct answer.


Robert is correct. The manufacturer method of testing the GFCI is to use the test button built on the unit. For outlets that are slaved to (downstream - such as kitchen outlets) one GFCI you will use the outlet tester button to trip the GFCI (indicates downstream outlets are properly wired).

There is a difference in the two test procedures that you need to be aware of. The manufacturers method actually imposes a simulated load between the hot and neutral inside the GFCI. The sudden current change trips the GFCI. The three light tester pushbutton creates a short to ground that trips the GFCI.

This second method will not work if the GFCI is protecting an ungrounded outlet. GFCI’s are approved for and will work with ungrounded circuits (two wire) but should have a notation applied to the outlet that indicates the circuit has no ground.

  1. the push (TEST BUTTON) on the GFCI receptacle.
    The answer here is No: (4)
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Robert. I agree that GFCI’s work on ungrounded outlets - the person being protected becomes the ground. However, I thought the reason for the notation on the outlet was because the integrated test button (as well as three-light tester) relies upon a ground wire to simulate the load or fault. We certainly do not run into ungrounded outlets with GFCI’s that often, but next time I am going to verify that you are correct. :slight_smile:

Ungrounded GFCI Outlets Offer Less Protection. For one, though ungrounded GFCI outlets offer you some protection (the GFCI outlet will sense when there is a ground fault and shut off), they will not protect your electronics in the chance of a ground fault. You need a ground wire and surge protector for the most protection against damaged electronics.

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The whole idea about GFCIs is to protect people who become the ground, regardless of whether or not there is a circuit ground. This is accomplished by sensing the current change that occurs when a short to ground (either a person or circuit ground) occurs. Were the test button on the GFCI to rely on a circuit ground to work there would be no way to test it in installations where there was no circuit ground.

These are experiments you can do in your own home. Why wait till you run into one? Inquiring minds want to know.


The test button relies on the neutral to perform the test so no EGC required. That’s why 2-pole gfci circuit breakers require a neutral even if the branch circuit doesn’t use one.

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If I find a GFCI receptacle that is open ground but doesn’t have the placard, I still write it up as open ground.



Kevin, is that your sticker or already in place?

The stickers come in the box when you buy a GFCI receptacle or you buy buy them in bulk.



I meant, do you mark the ones you test with a sticker if it shows NEG or just note it. I think you may have answered my question. :wink:

If no sticker is on the outlet cover I write it up as open ground.