HOT/NEU Reversal?

[drcampbell]

Help me interpret this:

3.0 volts green-to-white
119.2 volts green-to-black
120.9 volts white-to-black
Sperry 5-light tester shows "HOT/NEU REV".

House was probably built in the 1960s (?).
3-wire plastic-jacketed NM cable, full-size ground wires.
Plastic switch & receptacle boxes.
100-amp circuit breaker panel.

 

[MAC702]

Just this one receptacle, or all of them?

 

[Jon456]

Have you tried the tester in a known good receptacle? Have you tried a different tester in that receptacle? Have you checked the wiring on that receptacle and at the distribution panel?

 

[growler]

Help me interpret this:

3.0 volts green-to-white
119.2 volts green-to-black
120.9 volts white-to-black
Sperry 5-light tester shows "HOT/NEU REV".

Since the neutral (white) and ground (green) are bonded in the panel you wouldn't expect to see a voltage between them. Since you are getting a little less voltage from hot (black) and green (ground) than from hot (black) and neutral (white).

I would guess that there is a less than perfect connection on the ground path going back to the panel.

If you use an extension cord plugged into a different good circuit you could measure using a different neutral and ground path.

And you probably do have a hot and neutral reversed. I find them all the time after people change out receptacles.

 

[Jon456]

The 3V could be phantom voltage.

 

[mbrooke]

Was anything else running on that circuit at the time? How long is the circuit?

 

[romex jockey]

I'd be looking for my>>>>

~RJ~

 

[ptonsparky]

The 3V could be phantom voltage.

Yes,

I'd be looking for my>>>>

~RJ~

but I don’t have one!

OP, where did you find those ends for your DIY cable? I like it.

Guessing you did not mess up on the cable, I’d say the polarity is correct. You may be measuring neutral VD dependent on the load on that circuit but am inclined to think the PV.

The last option, reversal with a PP EG.

Did I cover all the scenarios?

 

[mivey]

I'm with growler.

Got a pic showing the wires and receptacle face at the same time?

Bring an extension cord from a good outlet on same leg and use it as a reference for measurements.

 

[drcampbell]

Small 1½-story bungalow, single-family detached.
Currently vacant, being prepped for sale. Absolutely nothing is plugged into any receptacle except the dishwasher & disposal. A few ceiling lights and the air conditioner were running at the time.

All of the receptacles on one circuit. (breakfast nook) Home run of maybe 30-40 feet, plus maybe 30 feet of cable interconnecting the four or five receptacles.
Every other receptacle in the house behaved as expected, but using only the Sperry tester and not following up with a voltmeter.

I did field-engineer an extension cord with the white & black deliberately reversed to see how the Sperry tester would respond, but succeeded only in tripping a GFCI. It didn't dawn on me to try it on another circuit (without a GFCI) until after I had returned home. I also plan to try a three-lamp neon-lamp tester, if I still have one and can find it.

Have not opened the panel to look.

I'm unconcerned about the three volts between white & green. If there's current flowing in the white and not in the green, there will be a little bit of voltage drop on the white and not on the green, and there will be a small voltage difference between the two.

Have you tried the tester in a known good receptacle? ...

Is there any such thing? Even if I brought a new receptacle & breaker, and connected them to a panel with three short lengths of THWN -- out in the open where I could see each one -- I still wouldn't have 100% confidence that there wasn't a gremlin somewhere, such as a loose neutral at the meter or ground offset voltage in the Earth due to a multiply-grounded distribution network.

 

[mivey]

Doesn"t matter about MGN.

If POCO neutral is at 2 volts to remote earth then the bond at the panel will make all of your grounds at 2 volts to remote earth. The neutral will be at 2 volts, excluding load voltage drop.

 

[GoldDigger]

The 3V could be phantom voltage.

Only if the EGC or bond is open. Possibly VD on neutral from another load. Hot/neutral reversal could be in termination to receptacle.

Sent from my XT1585 using Tapatalk

 

[mivey]

Only if the EGC or bond is open. Possibly VD on neutral from another load. Hot/neutral reversal could be in termination to receptacle.

Sent from my XT1585 using Tapatalk

After a long day, sometimes the gold and silver screws look the same.

 

[Little Bill]

If there were truly a hot/neu reversal, you would have read around 120V from white to green.
I have one of those Sperry testers and got the same hot/neu reversal. I checked and there was no swapped wires anywhere. Turns out I had lost either a neutral or hot, can't remember.

OP, did you try a load on the receptacle? That would show if you lost part of the circuit.

 

[growler]

I'm with growler.

If there were truly a hot/neu reversal, you would have read around 120V from white to green.

Sorry Mivey but I think Bill is right and I was wrong.

Folks it was a little after 3 AM and some idiot had just called and woke me up and then I couldn't just go back to sleep so I thought I would mellow out by reading. I see now I didn't clearly understand the test made by Drcampbell .

The first thing I do when I get a reversed polarity reading is pull the receptacle and see if there is a black wire on the same side as the ground ( neutral should be on same side as ground if the light is poor and it's hard to tell difference between silver and gold).

In this case if the receptacle is wired correctly and no obvious faults such as bad back stab. Then go to the next receptacle in the daisy chain.

Good luck and I hope the bad wiring is in a junction box and not a flying splice in a wall.

 

[kwired]

If there were truly a hot/neu reversal, you would have read around 120V from white to green.
I have one of those Sperry testers and got the same hot/neu reversal. I checked and there was no swapped wires anywhere. Turns out I had lost either a neutral or hot, can't remember.

OP, did you try a load on the receptacle? That would show if you lost part of the circuit.

Lost neutral is most likely thing. Lost hot and chances are you have no lights on such a tester. Seen same result with lost neutral before.

 

[K8MHZ]

When in doubt, always use a solenoid tester. Especially in older houses. DVOM readings can really be off due to their high impedance. You will be chasing your tail for days if you trust DVOM readings 100%.

 

[K8MHZ]

I haven't read anywhere that the OP pulled that particular receptacle and checked the connections. Did I miss something?

 

[ptonsparky]

I haven't read anywhere that the OP pulled that particular receptacle and checked the connections. Did I miss something?

I don’t think so.

 

[Jon456]

Have you tried the tester in a known good receptacle?

Is there any such thing? Even if I brought a new receptacle & breaker, and connected them to a panel...

You don't have to test it at the bungalow in question. Test it at your house. Test it at your shop. Even your "field-engineer an extension cord with the white & black deliberately reversed" can be tried anywhere, not just at the bungalow. My point was to test the device to see if it is still working as expected (i.e., doesn't have an internal fault which is causing the unexpected reading).

Anyway, I did some digging and found a possible condition that could explain the conditions that you're seeing. If your circuit has an open ground, and some connected device (for example, the air conditioner) is leaking some voltage onto that open ground (which could explain the 3V measured between ground and neutral), and you plug-in your tester, you are now providing a continuity path between the ground and neutral. Current will flow from ground to neutral through the neon lamp in the tester, and will indicate a reverse polarity.

I've also read that some of these neon testers can indicate reverse polarity simply if the circuit ground on that outlet is open, although that wouldn't explain the 119V reading between hot and ground.

My first recommendation is, as I stated previously, to remove the receptacle and see how it's wired. Also, open the distribution panel and check the wiring for that circuit (making sure the neutral and ground are landed properly, and that the neutral bus is properly bonded or not-bonded depending on whether this is the main service panel or sub-panel.

If you can find no obvious wiring problems, then use an extension cord from the distribution panel to get more accurate tests. Make an adapter that has 3 alligator clips with black, white, and green jumper wires to a NEMA 5-15R connector (include some kind of non-conductive cord to anchor the connector near the panel so the alligator clips don't get accidentally pulled off the panel connections). Attach the green clip to the ground bus, the white clip to the neutral bus, and the black clip to the output of the breaker for the circuit being tested. CAUTION: Do not connect to a different breaker or you may inadvertently get the wrong phase. Now you can plug one or more extension cords into your connector to bring your panel connections to the outlet to be tested. This will give you a known good hot, neutral, and ground connection for testing purposes.

I also recommend that you get a Fluke Stray Voltage Eliminator Adaptor:



This will eliminate "phantom voltage" readings caused by inductance from parallel-running branch circuit conductors. Phantom voltages used to drive me nuts when testing and tracing existing wiring until I got one of these.