Will a gfci work correctly without a ground wire?

Yes, a GFCI will work correctly without a ground wire. The GFCI is looking for the return current to come back on the neutral. If the return path of the current is any other path other than the neutral the GFCI will trip. Inside the GFCI are two current sensors (CTs) one on the line and one on the neutral. The 2 Cts appose one another when the current from the line returns on the neutral and the GFCI will not react. If only the line CT sees current but not the neutral, the GFCI will trip. If the current path is any other path than the neutral, then that is a ground fault. The ground path does not need to be back through the ground on the GFCI in order to trip. If the test button on your GFCI did not trip your GFCI when depressed then the GFCI is bad and should be replaced. Yes, a GFCI tester will not trip the GFCI if the ground wire on the GFCI is not attached. This is because there is no path (wire) for the line to return on for the tester other than the neutral, and the neutral is the intended path for the current. The neutral at your service entrance has a bonding jumper to ground.

This is the path the current will take back to neutral in the event of a ground fault. When you felt the tingle from your saw the amount of current it was not enough to trip the GFCI. A GFCI needs 0.03 amps fault current in order to trip. Be careful working with the saw in the rain. It only takes 0.05 amps ground fault to send your heart into ventricular fibrillation. If you have the older GFCIs they were set to trip at 0.20 amps. This was found to be to high to protect lives.

RE:

Will a gfci work correctly without a ground wire?

I recently answered a question where this applied. I received a lot of thumbs down so I deleted my answer. So now I want your opinions. My theory is no. A GROUND fault circuit interrupter will not work properly because....Essentially a gfci is a special breaker for a corded device within a circuit....

A GFCI will absolutely work without a ground wire. As stated earlier, and I know this thread is old, it detects a difference in current between the hot and neutral wires. Mike s answer was great, but some of his numbers were incorrect. His number of .05 amps is correct, that s all it takes to potentially kill you. However, a GFCI is designed to interrupt the circuit if a difference of 3 to 5 milliamps is detected (typical range) and that number is actually .003 - .005 amps. It s still possible to feel a tingle if the current passing through you is below the threshold of the GFCI, and although its uncomfortable, it s certainly not considered lethal. Test the GFCI monthly as recommended, if the rest function no longer works, replace it. End of story

It will offer protection against shock but not as much as one that is grounded. Basically the imbalance between the hot and neutral will be detected even without a ground but if the device you are using is not double insulated the shock may go through the person holding it while the GFCI detects the imbalance and then opens. While you won't get continuous shock, it could still be enough to cost injury or death. So, the best plan is to only use double insulated devices from an ungrounded plug or add the ground.

Hope that helps.

No ground needed. It's a common misconception. The GFCI measures the current flowing in the hot and neutral wires. It should be the same. If it's not (because the current is returning through a ground fault) then the GFCI will interrupt the circuit. No ground connection needed. But, the ground connection is needed for other protections to work.

How Does A Gfci Work

I've looked into this general issue for years, and have concluded that it is "controversial" even across experienced pros. Some will flatly suggest using one to protect expensive electronic equipment in lieu of a grounded receptacle, others that you can't get something for nothing, and no ground means no ground, period.

I certainly defer to the experts in this forum, and will look forward to their responses.

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If you're receiving a shock, then you're acting as the ground. This would be a 'fault' and the gfi will interrupt it.

Gordon's answer is correct imho.

A GFCI is essentially a circiut breaker itself. It detects spikes in amperage (if my memory serves me) and trips so that you don't blow your main breaker. It does not require a ground.