GFCIs with reverse polarity

[fbartlo (Frank Bartlo)]

I did an inspection this afternoon in which two GFCI outlets did not trip when I pressed the button on my GFCI tester, and it turned out their polarity was reversed. They were grounded, and the ground wire was correctly connected. They did turn off when I pressed their “test” buttons.

I have noticed that my tester does not work for non-grounded GFCIs, also. So I test those for GFCI functionality by pressing their “test” buttons.

While it would seem that GFCI function would not be polarity sensitive, I want to make sure before I make an incorrect call. Is it just the way the tester is designed (shorting hot to ground), or does reversal of the hot and “neutral” wires affect the GFCI function?

[jpope (Jeffrey Pope, CMI)]

Your testing device creates an imbalance or short between the ungrounded (hot) conductor and the grounding conductor.

When the polarity is reversed, there is no current distributed to the ground so the GFCI won’t trip via your tester.

[fbartlo (Frank Bartlo)]

That’s precisely what I thought. Thanks, Jeff!

[dchew (Dwight C. Chew, PE)]

I’d recommend that you check out the GFCI using the built in push button only. Once in a blue moon, you will explode the hand held tester. I didn’t believe it until it happened to someone I knew.

Also, never use a hand held tester unless you know where the actual GFCI is. There have been a couple of times where the GFCI was in the garage behind a spare refrigerator or freezer. I could have been responsible for ruining all of food in refrigerator if I’d use my tester.

[jpope (Jeffrey Pope, CMI)]

@dchew

I’d recommend that you check out the GFCI using the built in push button only.

There is no harm in testing these using an external source, although the manufacturers of the GFCI receptacles (such as Leviton) suggest using the internal test buttons as the only “accurate” method.

However, I have “tripped” GFCI receptacles using the internal test button, only to discover that the circuit had not opened - the receptacle was still energized even though the reset button had popped out. The newer GFCI receptacles, with “lock-out” tecnology, are designed to elimnate this condition, which can be created when a multi-outlet circuit has been improperly wired.

@dchew

Once in a blue moon, you will explode the hand held tester. I didn’t believe it until it happened to someone I knew.

I don’t see how this is possible. Could you explain what might cause this?

[Scott_Schultz]

I just did an inspection today in which the gfci outlet attached to the pool subpanel had reverse polarity but tripped when i push the test button the outlet (did not with the tester). Just recommend that the polarity get fixed as the outlet itself will trip if it has to.

[dchew (Dwight C. Chew, PE)]

@jpope

There is no harm in testing these using an external source, although the manufacturers of the GFCI receptacles (such as Leviton) suggest using the internal test buttons as the only “accurate” method.

However, I have “tripped” GFCI receptacles using the internal test button, only to discover that the circuit had not opened - the receptacle was still energized even though the reset button had popped out. The newer GFCI receptacles, with “lock-out” tecnology, are designed to elimnate this condition, which can be created when a multi-outlet circuit has been improperly wired.

I don’t see how this is possible. Could you explain what might cause this?

I got this information from several very experienced inspectors that I know in CREIA. I used to have a jpeg of one that blew up, I’ll see if I still have it.