HI skip

I am in Ontario, so people who set the codes here are not the same as at your QTH, but likely similar.

You have no basement??? but older ground-level floor and new upper floor I guess ?

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I believe yes technically , because it detects current that goes out on the hot wire BUT does not return on the neutral; say?? 10.02 amps out? and only 10.01 amps returning?? means .01 amps lost…maybe going thru you to ground == not good. ??On the old ones I opened up years ago, the two wires go together thru a small doughnut current transformer, and if ?everything returns the core of the ct see no NET magnetic field and does nothing more, but if some current is lost, the returning current wont be the same [wont balance the hot wire] and the CT will detect a NET ?flux and activate a mechanical trip likely using solid state circuits.

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You can buy small plug in the wall LED lights that indicate proper polarity, and I believe some have a button to test that a normal 3 wire gfi protected circuit is correct,?? but the latter needs a ground wire too .. which ?for a test could be from old copper plumbing.

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That was a long answer , yes 2-wire Can have GFI protection technically,? but your code may say otherwise, often depending on the age and situation. Here, new wiring must be 3 wire with GFI’s mandatory in SOME locations in a house, while some upgrading allows old 2 wire to be protected by a GFI, but a major house renovation might require all wiring to be three wire, and GFI’s in specific spots.

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It never hurts to put a GFI in from the safety point of view but you need to be sure that it opens the hot wire, and in old old wiring you might have to test which is the hot one.

One bad thing about my old GFI’s is that they can be tripped too easily by starting a variable speed fan motor nearby and on a different circuit.I have never investigated why. It is a 1/10 chance.

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it might need to be installed in a 3 wire system, where it goes to 2 wire, partly so you can use the test button on it.

That is about as far as I can go, as I am running on memory from 20+ years ago.

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I think I have garbled this up a bit, but I hope it helps some.

Don VA3DRL

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