I'm about to put my 1885 Victorian on the market. When I moved in, every receptacle except those in the newly-remodeled kitchen was a "2-prong." There are otherwise no ground wires or armored cable in the house. For convenience, I installed new "3-prong" plugs, ungrounded of course, throughout. I was fully aware of the consequences. (I'm an EE.) I have no doubt that any prospective new owner will have a home inspector come in to check things out. While more of an industrial/factory new build EE, I honestly wasn't aware that replacing the old receptacles with ungrounded 3-prong receptacles broke code. Now I do. I've familiarized myself with NEC 2014, and begun installing AFCI/GFCI breakers in the modern panel. I called Leviton and they sent me a pile of "GFCI Protected" and "No Ground Connected" stickers to place on all of my receptacles. So I think I'm good, right?

On my last trip to Lowe's to get some more breakers, I bought one of those cute little plug-testers -- the one with the GFCI test button -- for about 8 bucks. Yikes! When I plug the tester into any of the receptacles in the circuit for which I've installed the AFCI/GFCI breaker, my initial reading is "Open Ground." (Yay. It works!) But when I press the GFCI test button on the Southwire tester, the AFCI/GFCI breaker does not trip and I get a code for "Hot and Neu Rev." It would seem to me that the Southwire tester's circuitry is attempting to use the ground wire that isn't there to perform this test. Is that true? I remember reading something a while back that the home inspectors' circuit testers don't report GFCI tests properly on 2-wire, ungrounded systems. If that's true, is there a tester that "properly" tests a GFCI on a 2-wire system? (Note: Both the AF and GF test functions work perfectly on the breaker itself.)

I noticed that one of the modern, new-ish GFCIs installed in the updated kitchen also seems to lack a proper ground, and yet when I depress the "test" button on the GFCI it does trip it. But the Southwire's test button does not trip it. Five feet away is a properly-wired GFCI, which reads with my tester that a ground wire is present and this GFCI trips with both its internal "test" button as well as with the test button on the Southwire tester.

In an effort to reduce how many pages long my potential buyer's inspection report will be (peeling exterior paint, ancient furnace, etc.) I'd like to make sure that the wiring is at least up to code standards. If I have to install new 2-prong receptacles, I will, but I'd rather offer something better.

Here are my questions:

  1. Is this Southwire model 50020S-A receptacle tester really that bad that it can't trip a GFCI of any kind without a proper ground wire present?

  2. If the answer to #1 is yes, is the LED indication that the hot and neutral wires are reversed when I depress the "test" button meaningless?

  3. If the answer to #1 is yes, is there a proper receptacle tester that I should be using?

  • Could you test your theory, and open up one of the modern outlets, remove the equipment ground, and see if the tester no longer trips the GFCI?
    – Bryce
    Commented Dec 15, 2017 at 5:10
  • These testers use a resistor to the ground to create a 5-6 ma current on the ground this imbalance. Is what trips the GFCI, no ground no current no trip. With the newer GFCI outlets that electronicly test themselves all the time I am not sure how they trip during test without a ground possibly using the neutral before the toride or detection device to create an imbalance.
    – Ed Beal
    Commented Dec 15, 2017 at 16:38
  • Did you ever get this resolved? If so, please give a check-mark to the answer that helped you the most, or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer.
    – FreeMan
    Commented Aug 3, 2020 at 15:08

4 Answers 4


Use the Test Button on the outlet!

"GFCI testers" do indeed rely on a ground to provide a "controlled leak" past the GFCI so that it trips. The test you really need to be doing to test the GFCI protection is pushing the test button on the GFCI itself, as that leaks a bit of current line-hot to load-neutral (or vice versa) and thus trips the GFCI. Also, the indication you get from the testing device when the button is pushed is indeed no good due to that open ground.

  • ThreePhaseEel: Thanks for confirming my suspicions. Much appreciated. I wonder if I could build a proper/working GFCI tester out of a GFCI outlet. Imagine it all taped up nicely with two old multimeter probes connected to the line and neutral. Do you think such a device would trip a non-GFCI, un-grounded outlet that's on a circuit protected by a GFCI breaker? Now that would be a pretty cool and cheap solution to this problem, and wouldn't even require pulling a 200-ft ground wire behind you. Whaddaya think?
    – doogan78
    Commented Dec 15, 2017 at 18:28
  • Except that in a 2-wire system it is all an internal test. The plug-in unit measures the real-world conditions that will be presented to the potential buyers. One would assume they know about the safety, and especially fire-hazard implications of a 2-wire system. They may well decide to upgrade the entire place. When selling you never know the resources the buyer may bring to bear to fix little issues like this. For the seller there is probably more low-hanging fruit to be addressed - like mounting the HWH. Converting to a 3-wire system in a house this age doesn't make sense.
    – SDsolar
    Commented Dec 16, 2017 at 0:54

One test that will tell you that your receptacles are protected with the breaker is to bleed a bit of current to true ground from a given receptacle; a breaker should trip. An Ideal #61-164 Sure Test with their Ground Continuity Adapter #61-175 will give you the ability to make that test. This tester will prove that a particular two wire circuit with a three wire receptacle is indeed protected by a GFI breaker. It gives you the ability to provide a true ground to the receptacle being tested. FYI these home inspectors get their certification with a 2-week course. Don't expect them to listen to reason.

  • Thanks, Paul! You certainly answered my question! Yeah, those Ideals are pretty expensive, and it seems I can build a bush substitute out of spare stuff in the workshop. (See below) I look forward to seeing whether a $2 2-wire neon circuit tester can leak enough current to ground to trip a GFCI.
    – doogan78
    Commented Dec 15, 2017 at 18:16
  • Yes, but if you are willing to install true grounds to each outlet then your house is even more marketable. Upvote for this answer.
    – SDsolar
    Commented Dec 16, 2017 at 1:09
  • It will take 5 to 6ma to cause the fault . A 20k resistor hot to ground should do it. 120/.005=24k but the test button on the breaker is doing the same thing.
    – Ed Beal
    Commented Feb 12, 2019 at 20:45

You need a third path

GFCI devices simply compare the current on the hot wire to the current on the neutral wire. If they are the same, no ground fault. If they are different, it means current is taking a third path potentially through a human being.

Now, take your GFCI circuit tester and put it in a 2-prong cheater, the kind you use to plug a 3-prong plug into a 2-prong socket. This is, electrically, exactly the same as plugging your GFCI tester into an ungrounded 3-prong outlet. Now here's a question for a very smart EE. Where's your third path?

You can't have a ground fault with only 2 wires.

To fix your tester, get 100 feet of wire, anything will do. Run the wire from a known grounded point like your grounding electrode, to the tab on that cheater plug. Now you have a third path, because as you guessed, that GFCI tester leaks current from hot to ground.

Watch out for too-smart testers

The traditional 3-lamp tester is simply 3 neon lights between the 3 pins. Normally on a grounded plug, the hot-neutral and hot-ground lamps light, and the neutral-ground lamp (red) does not.

On your ungrounded outlets, only the hot-neutral lamp should light. However when you push the "test" button, the red neutral-ground lamp is now in series with the test button. No wonder it lights.

However, you may note that the legends on those 3-lamp testers are a bit of a "magic 8-ball". In an effort to fix this, manufacturers added some silicon electronics to some deluxe testers, to try to make the indications more clear. Of course these only get in the way of people who know how to read the lamps directly.

Getting clean with Code

A GFCI receptacle with no ground is not legal and will get written up unless it has a sticker that says the following:

No Equipment Ground

Every GFCI device is sold with a half dozen of these stickers, that's why. 90% of people do not affix them, and the remaining 10%, their partners tear them off because they're ugly.

A plain 3-prong receptacle without a ground will also fail; to be 3-prong, it must be GFCI, and there is no evidence that it is. Code also requires a sticker that says

GFCI Protected

So in most cases you'll be using both stickers. To deal with the "ugly" factor, the stickers can be self-made and don't need to be blue. You can get outlet covers that have this engraved into them, but they're more expensive than I would like. You can use white labeling tape e.g. out of a P-Touch, that looks reasonable on white cover plates.

  • Harper: You read my mind, man! I did check out the Ideal testers that Paul Logan recommended, but I didn't want to pay $350 for that kit when I could go the the basement and grab a 2-prong adapter and a 500' spool of MTW wire connected to the ground in the main panel and kinda gt the same solution, like you said. I was surprised that nobody else thought of the cheap "bush-fix", but that was before I found your answer hiding at the bottom of the page. ;-) Once I've done that, within a day or two, I should even be able to check whether the hot and neutrals are actually switched here and there.
    – doogan78
    Commented Dec 15, 2017 at 16:49

I like that: (Yay, it works) ;-) Take that for what it is telling you: Confirming that there is no ground.

First, to answer your question directly: GFCI means Ground-Fault Circuit Interrupter - a safety anti-fire hazard instrument.

They are designed to throw a mini-breaker if they detect leakage current on the ground lead, like if a hot wire touches a grounded enclosure inside an appliance or if it gets dropped into a sink.

Thus your pocket tester will not trip a GFCI outlet in a 2-wire system. You MUST have a ground wire for GFCI to function correctly.

Ground leakage is a clear indication that some of the power in an appliance is touching the grounded enclosure or otherwise finding its way to the ground lead.

Safety Rule #1 about Neutrals: never consider them to be a good ground. They cannot be counted on to provide the same safety protection of a third ground-only lead.

I have seen many situations where the neutral is the wire that comes loose or has some resistance between the appliance and the service panel somewhere and then two-wire appliances will give you a tingle when you touch them since the neutral is bonded to the enclosure. This can happen with refrigerators as well as toasters.

That is why we went to the three-wire system. SAFETY FIRST AND FOREMOST.

2-wire systems are a fire hazard.

My first home was mobile, and I had to not only add grounds but also convert it all to copper. It was much later torn down to make room for housing without having ever burned. I believe a lot of that was because I didn't rely on the resistance-prone chassis to be a part of the ground system. And yes, replacing entire wiring systems is a big job.

But you don't probably need to worry about this.

Depending on where you live, you most likely aren't "breaking code" by minor changes like outlets, especially in a house of that age.

In most US states there is no requirement to bring a house up to today's code.

Depending on where you live it may be required for major remodels.

A good clue is whether or not your modifications require a building permit.

Also, note that California requires all electrical work to be done by a qualified electrician.

Anybody with half a brain will know that a house of that era is going to be a 2-wire system. You still want to disclose it, and it won't surprise anybody.

Here is what I think you really want to know:

You do have a duty as a seller to disclose the outlets. You could keep quiet about it and roll the dice and just see what happens in a home inspection.

But that's a bad idea for a lot of reasons. Like if the house burns down a week after the new owner gets it insured.

As they say in real estate: "Disclosure is like voting in Chicago: Do it early and often" As long as you put it on the form, nobody can say you tried to hide the situation by changing the outlets.

As a buyer I would be looking for indications of foundation or roofing problems anyway. Allaying those concerns up front can help with the sales process. I always paid for my own home inspections before selling. More information helps the potential buyers make a decision more quickly.

Some simple issues (like hot water heater mounting) can be easily fixed by you, then others (like perhaps needing new carpets) can be offered as an allowance to the buyer, included in your asking price, so they can pick what they want. There is no accounting for taste so let the buyer do it themselves, if necessary.

Selling a house is a lot of fun. Then buying your next can be even better.

Enjoy the process and don't worry about any one thing too much.


  • 1
    Definitely do carpets as an allowance, Don't do what most sellers do, pick what you want to unload the house, not what any sane buyer would ever want.. White carpets, what is up with that? Commented Dec 15, 2017 at 7:52
  • 1
    No carpets here. 100% original oak hardwoods. Nicely done, too.
    – doogan78
    Commented Dec 15, 2017 at 16:24
  • SDsolar: I think you're mistaken about how a GFCI works -- and for the specific reason why my cheap Southwire tester doesn't trip the GFCI, but the test button of the GFCI does trip it -- it's because a GFCI compares the amount of current flowing through the hot and the neutral, and if there's a 5 to 6mA difference in current flow, it trips. The test button on the GFCI DOES NOT leak current to ground like the pocket tester does. Regarding "new construction," I recently completely remodeled a bathroom upstairs on a cloth wire circuit, and that's what started this whole exercise.
    – doogan78
    Commented Dec 15, 2017 at 16:27
  • SDsolar: Read what I wrote above again. "a GFCI compares the amount of current flowing through the hot [versus] the neutral, and if there's a 5 to 6mA difference in current flow, it trips." When you think about it, it's ingenious, and a lot safer than measuring the diff between line and panel ground. There's a GFCI outlet in my kitchen that's un-grounded, and it's internal test button will trip it. My pocket-tester will not.
    – doogan78
    Commented Dec 15, 2017 at 22:33
  • Indeed. That's why your tester is telling you there is NO GND - which you already know. After all is said and done, it is confirming what you put in the OP. You can't trip a Ground-Fault if there is no ground lead. (Lesson learned: the internal trip button has nothing to do with external conditions) In terms of safety, look at the data and what you know about the wiring. There is nothing to drain charges directly to ground. The real lesson is more legal than technological: My advice is to be sure any buyers have paperwork proving you already told them how things are wired...
    – SDsolar
    Commented Dec 16, 2017 at 0:47

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