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

@ hilde45 OP

Ok.

hilde45 OP283 posts   

03-22-2020   
 12:14pm   

Thanks, Jim. Later today, I will probably try this. Or tomorrow.

Before I proceed -- I want to be clear that so far I have tested multiple outlets on this daisy chain -- they all read as reversed.

I do not yet know how far back they go.

QUESTION: Are you suggesting that I try to *just* deal with the outlet nearest my gear? Or are you saying that I should deal with something at a prior step in the chain (nearer) to the breaker box?

@ hilde45

I had only read this far in your last post:

Thanks, Jim. Later today, I will probably try this. Or tomorrow.

When I then responded Ok.....

I just checked your thread and read the rest of your post.

Before I proceed -- I want to be clear that so far I have tested multiple outlets on this daisy chain -- they all read as reversed.

I do not yet know how far back they go.

Keep checking..... Keep checking the outlets on the circuit as you get closer to the electrical panel you will find the culprit. The chance the problem is in the electrical panel is slim to none, imo.

Jim

hilde45 OP

As far as finding the outlet closest to the panel is a bit tricky, as the wire which feeds things disappears into the ceiling and I'm not sure where it goes first. I'm sure where the 3rd, 4th outlets are, but not the 1st, 2nd ones. If the problem was at the panel, that's at least clear. If it's not at the panel, then I suppose I can just *try* what might be outlet #1, first, and see what I find.

Turn off the breaker and start checking for everything that is Dead. Including ceiling lighting. For the wall receptacle outlets a 120V drop light works great.  You can move pretty fast from one outlet to the next.

Use a piece of masking tape on the cover plate showing you have checked the outlet/s. You might want to make a second pass to make sure you didn't miss one.

Jim

almarg9,456 posts

03-22-2020
2:11pm

@Hilde45, when you measured the 4 volt difference between safety ground and the miswired "hot" terminal on the outlets was some or all of the equipment plugged in at the time? If so, I think it would be worthwhile to repeat that measurement with the equipment unplugged. In addition to the possible causes Erik has cited for the 4 volt measurement I’m thinking that applying 120 volts to the neutral of whatever equipment was plugged in could have resulted in AC leakage to ground within the component(s) that might have been responsible.

Jim ( @jea48 ), does that sound plausible to you?

I’m thinking that applying 120 volts to the neutral of whatever equipment was plugged in could have resulted in AC leakage to ground within the component(s) that might have been responsible.

Jim ( @jea48 ), does that sound plausible to you?

Al, (almarg), yes I would think that is a possibility too. Any connected load along the entire length of the branch circuit.


Also as I said previously.

1) VD, (Voltage Drop), on the neutral conductor due to the connected load on the branch circuit.

2) An induced voltage that is/may be created by the hot and neutral current carrying conductors onto the equipment grounding conductor.

4Vac would be pretty high in my opinion though.

Here is another possible reason:
IF there was a decent size load connected to the circuit at the time the 4 volts was measured it could be caused by a slightly loose and or corroded neutral connection anywhere from the panel neutral bus connection to the outlet the OP measured the 4 volts.

It would be interesting to know if the other branch circuit the OP measured 124Vac on is fed from the same Line,Leg, as the circuit he is experiencing the problem on. If yes, the 4V could very well be caused by a slightly loose and or corroded neutral wire connection in the branch circuit. That is one of the problems with using the duplex outlets for making the in and out connections for the branch circuit wiring. Though I have seen the same thing happen with a slightly loose and or corroded joint where a cheap hard plastic wirenut was used.


Though none of the above has anything to do with the AC reversed polarity problem the OP is experiencing.

Jim.

Correction:

jea483,299 posts

03-22-2020
2:57pm


Also as I said previously.

1) VD, (Voltage Drop), on the neutral conductor due to the connected load on the branch circuit.

2) An induced voltage that is/may be created by the hot and neutral current carrying conductors onto the equipment grounding conductor.

4Vac would be pretty high in my opinion though.

"4Vac would be pretty high in my opinion though."

That statement was meant for #2 only.
( An induced voltage that is/may be created by the hot and neutral current carrying conductors onto the equipment grounding conductor. )
It does not apply to #1.

hilde45 OP286 posts

03-22-2020
2:35pm

So, our house is a mixture of old/DIY and new (renovation); the problem is with the old part of the house.

If you would have said the branch circuit wiring you were having the problem with is DIY, I would tell you to hire an electrician to find and fix the problem/s.



Is the wiring in the old part of the house original wiring? Any idea what year that part of the house was built?

Just a guess the branch circuit wiring you have been troubleshooting is 14 gauge. The breaker in the panel is a 15 amp.
Just a guess there is maybe 6 to 8 duplex receptacles on the circuit. At present you have not posted if there are any ceiling light fixtures on the circuit.

By chance do you know what type of wiring the branch is? Is any of it exposed where you can see it? Maybe a back side of an unfinished wall? Maybe in the room the electrical panel is located?
Examples of the type of the branch circuit wiring:
Romex?
Thin wall rigid (EMT) Conduit and wire?
BX? (Wire with an outer flexible interlocked steel armor).

Guys, way to much time has been spent on this thread about the OP measuring a difference of potential, voltage, of 4 volts, from the neutral to the equipment ground contact on the receptacle outlet.
His biggest problem is reversed AC polarity he measured at the outlet. And as he has later posted the same reversed polarity he measured at other outlets on the same branch circuit.

As for the 4 volt the OP measured was it really 4Vac? Who knows.

I just checked a duplex receptacle that is fed by a 20 amp dedicated branch that is used to feed a treadmill. The branch circuit is #12/2 with ground Romex that is about 40ft from the electrical panel at best.

The test:
Multimeter, a Fluke 87. First test, meter set to AC volts. Default range auto scale. Reading,
power switch turned on treadmill only, standby state. Belt not running. Line voltage, 121.5Vac. Neutral to equipment ground, 9.4mv. (Meter allowed to settle down). Note, mv....
(Note Motor in treadmill is DC. That means the power supply is DC. Noise?)

I changed the range setting on the multimeter to 400Vac That is the closest range available above 122Vac.
Line voltage, 121.8Vac. Neutral to equipment ground contact, (after the meter settled down after about 10 sec or so), a steady 0.3Vac.

The above is for one finite test only. A different connected load, and type of load, no doubt would yield different results. No doubt a different, longer branch circuit with different connected loads would make a difference. I could go on and with different scenarios that would, could, make a difference in the neutral to equipment ground difference of potential, voltage.

What really matters? The conductivity, integrity (for a lack of a better word), of the equipment ground to be able to safely carry a ground fault current back to the source and hopefully cause the branch circuit breaker to trip open. (Note. In the event of a bolted ground fault event the instantaneous current could very well exceed 1000 amps.)


Jim
.

@ cissado

Good post except in the case of where the duplex receptacle device may have been used as a junction for the make up of neutral and Hot conductors coming in and going out of the outlet box.

We don’t know what type of wiring materials/methods were used for the branch circuit wiring.

What year NEC was in effect at the time? What were the AHJ electrical code standards/requirements back then for where he lives? Was conduit required in basements back then? Is there a chance the branch circuit is part of a multi wire branch circuit? What happens if he breaks the feed neutral at an outlet and the other circuit of the multi wire branch circuit has a connected load on it?

The OP is not an electrician. An electrician would know what to look for. Like another Hot circuit conductor passing through the box he is about to open a neutral. An open neutral on a multi wire branch circuit has killed many a electricians.

Jim

hilde45 OP288 posts

03-23-2020
11:44am



The reason I’m curious now, as I think I mentioned, is that I’m trying out my audio gear and have been shoved to an inconvenient side of my room because of this polarity problem; so, a fix would be helpful in terms of audio set up.

For this task only.

IF all you want to do is to correct the AC polarity at the outlet you want to plug in the power condition for your audio equipment. Nothing more at this time.....
If you want to do more than that I would suggest you hire an electrician. Better safe than sorry....



From one of my posts above:

Make 100% sure the breaker that feeds the outlet is turned off. Plug a lamp into the outlet. Turn the lamp on. The bulb lights. Go turn off the breaker. The light bulb is no longer lit. Use your mulimeter to verify the outlet is DEAD.

Carefully pull the duplex outlet from the wall box. HOPEFULLY there is only three wires connected to the outlet device.

If more than 3 wires connected to the outlet device,... stop..... Do not proceed.... Draw a picture on a piece of paper showing exactly how the device is now wired noting exactly how and where each colored black and white wires are connected on the outlet device. Make sure to note if the black and white wires are only connected to the side screw terminals. Or maybe also stabbed in the back into quick connect pressure terminals. **Look for any other color wire that may be passing through the outlet box.

Post back you findings.

Note, for the branch circuit wiring:
(Per NEC there shall be only one equipment grounding wire connected to the equipment ground terminal on the duplex receptacle outlet device. All equipment grounding conductors within the outlet box shall be joined/jointed together with a pigtail extended out for connection to the duplex receptacle device.) If the outlet box is metallic, made of steel, the box shall be grounded as well.

Jim.

@ hilde45

Would you please tell us what make and model your multimeter is? Please!

Does it have an auto scale? Is that what you used when you read/measured the 4 volts AC? Are you sure it was 4 Volts or was it possibly 4mv ( 4 millivolts)

Or did you have to set the meter to a voltage scale above, say 150Vac or something like that?

Also when you measured for the neutral to equipment ground voltage did you allow the meter to settle down to a steady state constant voltage?
If you don’t remember would you please repeat the test.

Jim

Al, (almarg),

I drew 3 vertical parallel lines on a piece of paper. One representing the Hot, one for the neutral and the other the equipment ground. At the top of the drawing I drew a horizontal line connecting both the neutral line and equipment line together. (Representing how the equipment grounding conductor is connected to the neutral at the electrical panel.)

At the bottom of the neutral and equipment ground lines I connected a digital meter.

Above the meter I drew the symbol of a resistor. I connected one lead to the hot and the other lead to the equipment ground. The resistor represents the leakage you spoke of in your post.

With the power switch of the equipment in the off position there will not be any hot and neutral current carrying load. Therefore there can not be VD. No VD, no difference of potential between the neutral conductor and the equipment grounding conductor. (At least originating within the branch circuit, and the piece of equipment connected to the branch circuit.)

Using your leakage theory I see what you mean when the mains Hot conductor is directly feeding the primary winding of the power transformer. I can see if there is a leakage to the chassis there would be current on the equipment grounding conductor. I am not sure you would measure a difference of potential from the equipment ground to the open switch open neutral though. Especially if the neutral conductor and equipment ground conductor are at the same ground potential.

Now if the leakage turns into a ground fault event and there is then considerable current causing a VD in the Hot / equipment ground (ground fault) circuit then indeed there would be a difference of potential from the equipment ground to the open switch open neutral.

I could be wrong though..... It wouldn’t be the first time.

Jim
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hilde45 OP269 posts

03-20-2020
7:26am

@bryhifi I have a digital multimeter. I use it to test car batteries. I suppose I might use that, too, no? In any case, I can get the three prong outlet if necessary.

The DMM will work just fine.

1) Set the meter to AC ~ auto volts or an AC ~ voltage scale above 150Vac.


2) Insert one test lead probe in the "U" shaped equipment ground contact hole of the wall outlet. Make sure you make good contact to the ground contact. Insert the other test lead probe into the Hot contact slot of the outlet. Make sure you make a good connection to the Hot contact. (The Hot contact is the smaller of the two slots.) You should read 120Vac nominal volts. *(If the reading is bouncing all over the place that is what is called a phantom reading, not a true reading.)
If you get a solid good 120V nominal reading that will tell you two things. The AC polarity is correct and a ground is present.

IF you do not measure 120 Volts nominal. That can mean Two things.. NO equipment ground, or Hot and Neutral reversed polarity.

3) Measure for voltage from the equipment ground contact to the neutral contact. The neutral contact is the larger of the two slotted holes on the outlet. Make sure the two DMM probes are making good contact. If you measure a good solid 120 nominal voltage then the Hot and Neutral branch circuit wires are reversed on the receptacle outlet. If you do not measure any voltage then you do not have an equipment ground.

Jim

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heaudio123135 posts  

03-20-2020  
 8:58am  

"3) Measure for voltage from the equipment ground contact to the neutral contact. The neutral contact is the larger of the two slotted holes on the outlet. Make sure the two DMM probes are making good contact. If you measure a good solid 120 nominal voltage then the Hot and Neutral branch circuit wires are reversed on the receptacle outlet. If you do not measure any voltage then you do not have an equipment ground."

I think some clarification here for a novice. When you measure between ground and neutral at a receptacle, most multimeters will indicate some voltage, i.e 0.1 - 2.0V approx.

heaudio123

I think some clarification here for a novice. When you measure between ground and neutral at a receptacle, most multimeters will indicate some voltage, i.e 0.1 - 2.0V approx.

True, If #2 of my previous post above is met. Therein a properly wired receptacle outlet with a Correct AC polarity, and an equipment ground is present.

For the novice a difference of potential, voltage, measured between the neutral conductor and the equipment grounding conductor on branch wiring can be caused by, at least, two things.

1) VD, (Voltage Drop), on the neutral conductor due to the connected load on the branch circuit.

2) An induced voltage that is/may be created by the hot and neutral current carrying conductors onto the equipment grounding conductor.

Jim

almarg9,459 posts

03-23-2020
2:59pm


Hilde45, when you measured the 4 volts while the system was plugged in, were the components in the system turned on, or were they turned off or at least in standby? And as far as you know was anything else that is on the same branch turned on at the time?

If a lot of stuff was turned on at the time it increases the likelihood that the explanations cited by Erik and Jim apply. If not, it increases the likelihood that my hypothesis applies, namely that applying 120 volts to the AC neutral input of the component(s) resulted in excessive AC leakage to ground, mainly via their power transformers. Or, as heaudio123 alluded to, if significant current was being drawn by the components or other things the cause could have been a combination of both factors.

If my hypothesis was the main contributor, though, that issue should go away once the hot and neutral connections are reversed to what they should be.

Best regards,
-- Al

Al, (almarg),

First off we don’t know if the OP’s test is valid. We are only assuming that there is/was an actual difference of potential of 4 volts between the neutral conductor and the equipment grounding conductor.

What I do know unless a load is connected to a branch circuit there will not be an actual difference of potential between the neutral conductor and the equipment grounding conductor. (To quantify that statement we assume the equipment grounding conductor is connected to the neutral conductor at the main electrical service panel)

On the same dedicated circuit that I ran tests on yesterday, using a Fluke 87 DMM, with nothing plugged into the duplex outlet I just measured a mains voltage of 121.8Vac. From the neutral contact to the equipment ground contact I measured 1.0mV - 1.1mV. Jmho, that is a phantom voltage and not a real, actual voltage reading.

I could intentionally add series resistance to the neutral conductor, or to the equipment grounding conductor and that would not cause, on its’ own, a difference of potential, voltage, between the two conductors. (No Connected load)


//////////////

For all:

What can, does, cause an actual voltage to exist on the equipment grounding conductor is a connected load on the branch circuit. Can’t have a difference of potential between the neutral conductor and equipment grounding without a connected load on the hot and neutral conductor. The voltage can be an induced voltage caused by the current carrying Hot and neutral conductors. Though in that case the voltage will be normally in the mV range.

The other thing that causes a voltage to exist between the neutral conductor and the equipment grounding conductor is VD (Voltage Drop) on the circuit caused by a connected load. No load, no VD....
Causes of voltage drop:
http://www.adamselectric.coop/wp-content/uploads/2015/02/Voltage-Drop.pdf

//////////////

Al, (almarg),

If a lot of stuff was turned on at the time it increases the likelihood that the explanations cited by Erik and Jim apply. If not, it increases the likelihood that my hypothesis applies, namely that applying 120 volts to the AC neutral input of the component(s) resulted in excessive AC leakage to ground, mainly via their power transformers.

I gave your theory some thought and I can see where there would be an increase of current on the equipment grounding conductor as more leakage was present but I cannot see where the voltage would increase. If anything the voltage would decrease. Wouldn’t more leakage translate into a lower neutral to equipment ground resistance? The lower the resistance, the higher the current, the lower the voltage.
Extreme example. 0 ohm resistance between the neutral and equipment grounding conductor.

Jim
.

@ hilde45 OP

As djones51 said, start with the wall duplex receptacle you tested that has the reversed polarity. (Hot and neutral wires reversed on the outlet device.)

Make 100% sure the breaker that feeds the outlet is turned off. Plug a lamp into the outlet. Turn the lamp on. The bulb lights. Go turn off the breaker. The light bulb is no longer lit. Use your mulimeter to verify the outlet is DEAD.

Carefully pull the duplex outlet from the wall box. HOPEFULLY there is only three wires connected to the outlet device.

If more than 3 wires connected to the outlet device,... stop..... Do not proceed.... Draw a picture on a piece of paper showing exactly how the device is now wired noting exactly how and where each colored black and white wires are connected on the outlet device. Make sure to note if the black and white wires are only connected to the side screw terminals. Or maybe also stabbed in the back into quick connect pressure terminals.

Post back you findings.

Note, for the branch circuit wiring:
(Per NEC there shall be only one equipment grounding wire connected to the equipment ground terminal on the duplex receptacle outlet device. All equipment grounding conductors within the outlet box shall be joined/jointed together with a pigtail extended out for connection to the duplex receptacle device.) If the outlet box is metallic, made of steel, the box shall be grounded as well.

djones511,315 posts

03-21-2020
12:19pm

This first one is reversed pull it out and see if the white wire is on the bronze screw side and black wire on the silver screw side which would be wrong. If not look at the receptacle prior where it’s drawing power from for the same thing. Black to bronze, white to silver, bare wire to green screw is how they should be.

@ hilde45 OP


You will also notice the color of the terminal screw heads are on the same side of the Hot contact (small slot), and neutral contact (longer slot), of the duplex outlet.


If you acknowledge, post, you have read this today I will check in on the thread through out the day. You can also PM me through the Agon system if you so choose as well.

You are not required by the NEC or possibly/more than likely by your AHJ (Authority Having Jurisdiction) in your area to be an electrician to change out an outlet. I would strongly suggest though you feel confident that you have the know how to do it though. IF in doubt hire an electrician.

Jim

@ cissado

cissado19 posts

03-23-2020
11:26am



2 tips. Be conscious of any switches outlets when testing, so there are no surprises.
When trying to find the first receptacle box, you can disconnect one pair of wires from the receptacle. THEN reapply power to find out if you’re in the beginning or middle of the circuit.

@ cissado
Reading your entire post from 03-23-2020 you have a background in electrical wiring/methods.


This was my response to your post.

jea483,307 posts  

03-23-2020  
 12:03pm  

@ cissado

Good post except in the case of where the duplex receptacle device may have been used as a junction for the make up of neutral and Hot conductors coming in and going out of the outlet box.

We don’t know what type of wiring materials/methods were used for the branch circuit wiring.

What year NEC was in effect at the time? What were the AHJ electrical code standards/requirements back then for where he lives? Was conduit required in basements back then? Is there a chance the branch circuit is part of a multi wire branch circuit? What happens if he breaks the feed neutral at an outlet and the other circuit of the multi wire branch circuit has a connected load on it?

The OP is not an electrician. An electrician would know what to look for. Like another Hot circuit conductor passing through the box he is about to open a neutral. An open neutral on a multi wire branch circuit has killed many a electricians.

This was your response to my above post.

cissado19 posts  

03-23-2020   
4:17pm

I’m not sure what this means exactly. Maybe because I wasn’t clear in my post. I usually am not clear... it’s my bad writing skills.
I just meant the first receptacle may have been fed from a light fixture. Also, that the wiring inside the light fixture box could be wrong.

It was this part of your post from 03-23-2020 that I was addressing.

When trying to find the first receptacle box, you can disconnect one pair of wires from the receptacle. THEN reapply power to find out if you’re in the beginning or middle of the circuit.

Maybe I was not clear. The point I was trying to make, because the OP admittedly called himself a novice and knows very little about electrical power systems and or electrical wiring and wiring methods, it may not be a good idea to open a branch circuit neutral even though the OP turned off the breaker that feeds the circuit he is working on.
We don’t know, and the OP definitely doesn’t know, if the branch circuit he is dealing with is a 2 wire with ground branch circuit ( Hot, Neutral, and ground), or possibly part of a 3 wire multiwire with ground branch circuit. Multiwire, therein 120/240V 3 wire multiwire branch circuit consisting of 2 hot conductors with a shared neutral conductor.
(Two 120V circuits that share a common neutral conductor.)


Best regards,
Jim

.

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.

@ hilde45 OP

Yeah, you got a lot going on there. And all that on #14awg wire to boot. It’s been like that, I imagine, for many years and you didn’t know it. That is, unless the 15 amp breaker was tripping occasionally from being overloaded.

You didn’t know the AC polarity was reversed at the wall outlets either, until several days ago. (Not mentioned in this thread, reversed AC polarity can have an affect on the sound of an audio system. But that’s for another thread.)

As for the 4 volts you measure from the neutral to the equipment ground that really doesn’t matter. The 4 volts may not even really exist. It could just be phantom voltage created by the multimeter. Even if the 4 volts is real it’s to low to be an electrical safety/shock hazard.

This all started because you bought a ’ Panamax, Max 1500 surge protector and line conditioner’. Then when you plugged it in it said you had an AC mains line fault. If you hadn’t bought the darn thing you wouldn’t have been going in circles the last several days trying to figure out what the problem is.

Options, the way I see it.

1) There is way to much going on with the branch circuit wiring for you to repair. Not to mention your qualifications.... You maybe a great teacher, but a lousy electrician... An electrician could spend a couple days, maybe more, straitening out the mess. It all comes comes down to time and money. You have the money, he/she has the time.

2) Reverse the Hot and neutral wires at the duplex receptacle outlet the power conditioner will be fed from. I assume the duplex outlet is used to feed all of your audio equipment.

3) If all of your audio equipment will be plugged into the power conditioner you could reverse the Hot and neutral wires on the power cord plug of the cord used to feed the power conditioner.

4) Hire an electrician to install a new 20 amp dedicated branch circuit for your audio equipment.



Note:
There are instances where reversed AC mains polarity can be an electrical shock hazard. In the case of screw in light sockets. If the mains polarity is reversed and the circuit is hot, on, feeding the light socket the outer screw shell of the socket will be Hot with respect to ground. To lesson the likely hood of receiving an electrical shock in the event one hand is in contact with the outer shell of the light bulb, while it is in contact with the shell of the light socket, and the other your other hand is touching a grounded object MAKE SURE the switch is in the off position. If the light has a cord and plug you can always just unplug it from the wall when replacing a burned out light bulb with a new one one.



Jim

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hilde45 OP303 posts

03-26-2020
11:12am

The 4v issue is weird, because the multimeter does not read 4v on a properly wired outlet on a different circuit.

Apple to oranges, imo.
What is the wire gauge size of the other branch circuit? What is the total length of the branch circuit? What is the total connected load on the circuit? What is the type of devices that are connected to the circuit? How many CFL and or LED lights are connected to the branch circuit? What is the voltage drop on the circuit that you didn’t measured the 4V neutral to ground voltage?


You have all kinds of things going on with the branch circuit where the wall outlets have reversed polarity issues. You now know the branch circuit feeds outlets on the first floor and the basement. You now know it feeds ceiling lighting. How many CFL and or LED lights? They spew all kinds of harmonic noise back on the AC mains. Who knows what that does to your cheap multimeter.

There is still a very good chance the 4V is caused by voltage drop. Now that you know the branch circuit feeds outlets and ceiling lighting on the first floor, not just the basement, turn off all the connected loads that are connected to the branch circuit. Check for the neutral to ground voltage again. No load, no voltage drop.

As for the power conditioner showing an AC mains ’Line Fault’ condition. Correcting the AC polarity reversal problem, will solve the power conditioner 'Line Fault' problem.


Jim.

@ hilde45 OP

(If the plug on the power conditioner cord is a molded plug.)

All you need to do is cut the plug off the cord that feeds the power conditioner and install a new plug. You will reverse the Hot and neutral wires of the cord on the new plug’s terminals.
Neutral wire to black color screw on the plug.
Hot wire to the silver color screw on the plug.
Green ground wire to the green screw terminal.


125V 15 amp 5-15P plug.
https://www.homedepot.com/p/Leviton-15-Amp-125-Volt-Industrial-Grade-Straight-Blade-Plug-In-Black-Wh...
.