Line fault at the outlet -- do I need an electrician?

I'm somewhat perplexed by the latest measurements, and I can't readily envision a miswire (or even multiple miswires, perhaps at the panel as well as at one or more of the outlets) that could account for these findings.  But what I would say at this point, given the possibility of multiple unknown miswires, is DO NOT ASSUME THAT TURNING OFF THE BREAKER WILL KILL THE ELECTRICITY TO THE OUTLET.  

Best,
-- Al

I always use a little light tester in the receptacle or the screws on the side even after throwing the breaker.

Thanks Al. Your use of all caps is exactly what they were meant for.

I won't open an outlet until I'm 110% sure it's off. After all, I've pledged my life to the COVID virus; I can't cheat it by electrocuting myself. (Please pardon the gallows humor. It's all I've got left, except for an obsession with audio.)

hilde45 OP299 posts

03-25-2020
12:26pm

OP again:
I’m pretty sure I unplugged everything on the chain of outlets.
I have not thrown the breaker yet.
All outlets on chain read as reversed:
* the negative plug input reads as 120v, more or less
* the positive plug input reads as 3.4v, more or less
* Unplugging all things in the outlets made no difference to the 3.4v reading.

* Unplugging all things in the outlets made no difference to the 3.4v reading.

@ hilde45,

Did you find any ceiling lights that are fed from the circuit? Did you look everywhere you could think of in the house where some light/s, appliance, equipment, that was dead when the breaker was turned off?

Without any load connected to the branch circuit I can’t see where a 3.4V from the neutral to ground is coming from.

I looked at, what I think is, your multimeter. The user manual is worthless. You said you set the selector switch to 200Vac, which is the correct setting for 120V. I am going to take a wild guess and say the 3.4V is actually 3.4mV (millivolts). I would like you to check the voltage again. This time look closely at the screen on the meter for mV, therein 3.4 mV. If it is 3.4mV, imo, it is a phantom voltage.

The Fluke 87 when the selector switch is set to ~ v (AC volts) the meter defaults to the auto range. If the voltage is less than 1 volt it will give a display in mV. The mV appears lightly to the right of the number displayed. Maybe that is how your meter displays a millivolts measurement.


Just for the heck of it I ran another test. I used a convenience outlet circuit that is about 100ft long from the panel to the farthest outlet on the circuit. Wire is 12/2 with ground Romex.   
(6 duplex outlets are on the circuit. They are not daisy chained....)

For the load I used a portable vacuum cleaner with a nameplate load rating of 12 amps.
The Test.
I picked the farthest outlet on the circuit from the electrical panel. Nothing plugged into the circuit. No connected load.
Mains voltage at the receptacle 122.3Vac.
Neutral to equipment ground 5.6mV.

With the vacuum cleaner plugged into the outlet, vacuum turned on.
Mains voltage 117.1Vac.
(122.3V - 117.1V = 5.2V Voltage Drop.)
Neutral to equipment ground measured 2.3Vac.

Jim.