HOT/NEU Reversal?

[growler]

I agree. Which is why I stated (as did you) that he needs to find where the old 2-wire NM meets up with the new 2+G NM. I'm guessing that whoever did the wiring for the addition made some kind of ground connection at that junction and it has either become a bad connection, or the source of the ground was poor to begin with.

Around here people will extend an un-grounded circuits with three conductor cable and never worry about a ground connection. It doesn't show up until someone plugs in a tester so no one notices.

I love chasing down missing grounds on home inspection reports.

Yes, when he finds where the new cable connects to the old it should become apparent what was done.

If he doesn't have a ground then he may have to GFCI protect those three pronged receptacles or run a new home run ( or at least an equipment ground wire).

 

[Jon456]

Around here people will extend an un-grounded circuits with three conductor cable and never worry about a ground connection. It doesn't show up until someone plugs in a tester so no one notices.

I love chasing down missing grounds on home inspection reports.

Yes, when he finds where the new cable connects to the old it should become apparent what was done.

If he doesn't have a ground then he may have to GFCI protect those three pronged receptacles or run a new home run ( or at least an equipment ground wire).

We know the ground isn't missing entirely. Unless he has a bootleg ground (with a poor connection).

 

[gar]

190706-0940 EDT

drcampbell:

So far I have not seen that you have used an extension cord to get some good voltage reference points.

With an extension cord, an 0.1 V resolution meter on a range that reads 120 V, a 10 ohm test load, a magnetic field sensor, additional wire, and some misc parts you can determine where current flows, direction of power flow, and determine within an area where your problem originates, and not initially open any box.

.

 

[drcampbell]

The branch circuit in question almost assuredly has a high-resistance ground. In my book, that's something in the electrical system that's "not working" and requires troubleshooting and correction. If Fluke makes their LoZ setting in their 117 multimeter the same as they make their SV225, then that bad ground has a total resistance of almost exactly 24,000Ω. I didn't just pull that number out of the air.

If my meter is to be believed -- and I'm not so sure I believe it -- there was 1.5 MΩ in parallel with 10,000 μFarads between white & ground.
(The main breaker was off when I measured that; nothing in the house was energized. The branch breaker was off; nothing else should have been connected to this circuit)
I have no idea where 10,000 μFarads would have come from. I measured only 20 nanoFarads on an entire 250-foot roll of NM cable.

I am not sure what the problem we are trying to solve actually is. I may have missed that somewhere. ...

There is no problem. They neglected to include a ground wire when they added on the breakfast nook, but one's in there now.
I just want to understand why my Sperry tester interpreted a missing ground wire as a hot/neutral reversal.

 

[K8MHZ]

There is no problem. They neglected to include a ground wire when they added on the breakfast nook, but one's in there now.
I just want to understand why my Sperry tester interpreted a missing ground wire as a hot/neutral reversal.

You may have to tear the tester apart to understand how it works.

I own several plug in testers and sometimes they don't always indicate the same problem on the same receptacle. I only use them for quick checks anyway. And less and less at that.

 

[ptonsparky]

You may have to tear the tester apart to understand how it works.

I own several plug in testers and sometimes they don't always indicate the same problem on the same receptacle. I only use them for quick checks anyway. And less and less at that.

. Way back I used a BFH on a 4-way so I could see its operation.

 

[K8MHZ]

. Way back I used a BFH on a 4-way so I could see its operation.

I have taken many things apart in order to understand them. I like to be gentle, so instead of a BFH, I use pry bars and saws. I have a breaker apart in my collection so I can see the innards.

 

[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".

There is no problem. They neglected to include a ground wire when they added on the breakfast nook, but one's in there now.
I just want to understand why my Sperry tester interpreted a missing ground wire as a hot/neutral reversal.

You do still have a problem. You need to find where that 2 wire cable connects to the 3 wire cable.

You don't have a clearly open ground. If you did then the tester would give the correct indication.

What you have is some hack wiring in a junction box or flying spice and those testers don't have an indicator light for that.

 

[kwired]

I have taken many things apart in order to understand them. I like to be gentle, so instead of a BFH, I use pry bars and saws. I have a breaker apart in my collection so I can see the innards.

The best way to view breaker innards and see how things work is to have one with clear plastic case like you might find on display at supply house or a trade show booth.