If an open ground outlet can be corrected by replacing it with a GFCI outlet, why is it that when I use a GFCI tester it does not pop off an open ground GFCI.

 

An open ground cannot be "corrected" by replacing it with a GFCI, in that the ground is still open. It is corrected, however, in that it now conforms to code.

The internal GFCI tester still works without a ground, because it can simulate a ground fault (it doesn't actually create one). However, an external plug-in tester does not trip the GFCI because it cannot successfully create a ground fault without a ground (i.e., it has no place to divert any current). If you could create a ground fault by another way, it would still trip. There are no really safe ways to create such a fault, so I don't encourage you to try. You can trust the internal tester.

 

Thank you for your promt reply. The reason I ask is that when doing home inspections I write that the GFCI it not working properly because it doesn't pop off and the reason is that it shows open ground. I call it a hazard and recommend it be fixed. I do the same when it shows incorrect polarity. Is this right?

 

You are correct to note open grounds for the information of your client. But when a GFCI is involved, there is no code violation in an open ground. In an older house wired before grounding was common, it is usually impractical to suggest that all open grounds be corrected prior to the sale. But the buyer should be made aware of the issue in case they have a lot of equipment that requires grounding (computer, electronics, etc.). Few people have an absolute need for grounding everywhere.

The fact that your plug-in tester does not trip the GFCI when you press the little button on an open ground receptacle means nothing. It is not an additional problem. When your tester indicates an open ground, you should not conduct that test. Instead, you should use the "TEST" button on the GFCI itself, and only that test button. To see if downstream receptacles are also GFCI protected, it is sufficient to note that they lose power when the "TEST" button is pushed on the upstream GFCI receptacle. If it passes these tests, then the GFCI protection is as good as it can be.