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Some circuitry in my old house is just two wire w/o ground and as I'm renovating I replace these outlets with GFCI if I'm not pulling two wire w/ground. I've found such an outlet that shows HOT/NEU REVERSE either way I attach the hot and neutral wire to the GFCI outlet. What is going on here?

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  • Are you connecting to the load? Terminals instead of to the line. Your hot and neutral feeder needs to go on the line terminals. This is where I would look for the problem.
    – Ed Beal
    Commented Dec 27, 2021 at 20:12
  • With no ground, how will the GFCI tell which wire is hot and which is neutral? Commented Dec 27, 2021 at 20:13
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    @PhilFreedenberg The GFCI actually does not care which is which, it just looks to see whether hot and neutral are equal. Commented Dec 27, 2021 at 21:13
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    Those 3-light testers are optimized for detecting wiring mistakes in new construction, not wiring failures in proven wiring. As such, their "what's wrong" answers are extremely wrong and misleading. Peel the label off and throw it in the trash. The yellow-yellow-red lights are useful. Commented Dec 27, 2021 at 21:13
  • Can you post photos of the inside of the box in question please? Commented Dec 28, 2021 at 3:38

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First, the lack of a ground wire does not imply lack of grounding. Older construction often brings ground via the armored cable or metal conduit to metal boxes, and receptacles and switches can pick up ground via their mounting screws. Receptacles do not do this reliably unless they are marked "self-grounding".

You haven't mentioned this, but you are using a 3-light tester both for GFCI testing and also to detect wiring problems. Those 3-light testers are extremely unreliable because the labeling is written for wiring mistakes in new construction. The labeling is completely wrong for troubleshooting wiring failures in something that was properly wired.

On a grounded receptacle: The tester should indicate 2 yellow lights. When the "TEST" button is pressed, it should immediately trip the GFCI and the tester should indicate all dark. (because the GFCI tripped).

On an ungrounded receptacle: The tester should indicate 1 yellow light (middle). While the "Test" button is pressed, the GFCI should not trip. The light indications become meaningless, you might expect center yellow and red while you're holding the button down, but that is a testing artifact.

Always hook things up correctly. When "wiring correctly" and "optimizing for favorable messages on a tester" conflict with each other, always wire correctly.

When installing GFCIs, put all wires on "Line" (read the instructions for how each screw takes 2 wires). Do not use the "Load" terminals unless you understand how downline protection works and want to use it, note instruction 8(C) re: installation of "GFCI Protected" stickers. Using "Load" and multiple GFCIs results in redundant protection and great difficulty resetting. Here's how to untangle that when you do it by mistake.

You MUST use "No Grounding Conductor" stickers on all GFCI-protected outlets without true grounds. If you don't like the look of the provided stickers, feel free to make them on a Brother or P-touch label maker: any method is allowed except hand-written.

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  • Check, check, check, check to the many questions and answers, thanks. I've upgraded many of the old two wire receptacles to code with GFCI outlets, stickered them appropriately and the simple receptacle tester performs as expected (indicates no ground and button doesn't trip the GCFI). It is just this oddball that doesn't just show "no ground" but indicates the hot/neu reversal regardless of the way I wire it. I will leave the hot wire connected to line/gold on the GFCI. Commented Dec 28, 2021 at 0:44
  • When you use a GFCI in a receptical with no ground connection, how do you verify that the GFCI is working correctly? It isn't able to leak current to ground to simulate a fault, so the test button won't work. However, GFCI outlets do fail, so they need to be testable.
    – Duncan C
    Commented Dec 28, 2021 at 0:55
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    The test button built in to the device will work just fine without a ground wire.
    – nobody
    Commented Dec 28, 2021 at 13:05
  • The internal test can either leak current from the load side back to the line side, or run a third wire through the sense transformer. Neither option needs ground. Example schematics: electroschematics.com/gfi-ground-fault-interrupter-wall-wart
    – nobody
    Commented Dec 28, 2021 at 13:16

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