# N-G Potential >5VAC, no load



## ewicky (Oct 24, 2016)

It seems obvious to me that a more probably cause is the the EGC is not properly bonded to neutral at the service, but when I proposed that theory, the maintenance supervisor insisted "the building was grounded properly" and that they would not shoulder the cost for a real contractor to come out and check my service. He also insisted something in my equipment must be causing the problem (even with every single plug (as well as CATV) in my apartment unplugged, even the lamp behind desk, etc.


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## PlugsAndLights (Jan 19, 2016)

Would one receive an "alarming shock" from 5V? 
Maybe I'm nit-picking. 
P&L


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## backstay (Feb 3, 2011)

ewicky said:


> It seems obvious to me that a more probably cause is the the EGC is not properly bonded to neutral at the service, but when I proposed that theory, the maintenance supervisor insisted "the building was grounded properly" and that they would not shoulder the cost for a real contractor to come out and check my service. He also insisted something in my equipment must be causing the problem (even with every single plug (as well as CATV) in my apartment unplugged, even the lamp behind desk, etc.


Your apartment building may be properly grounded, but does he even know the difference between grounded and grounding? This is a bonding issue. Time to call the electric police, or apartment police. I hate to say this but here goes. What if you bonded at your panel? Just to see if your problems go away. Just for "testing purposes. I'm sure somewhere in the building there is already a ground/neutral bond down stream from the service. Very few building I work on don't have some parallel connections. They haven't burned down yet. A clamp on amp meter would tell you.


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## splatz (May 23, 2015)

I doubt that 5v is enough to cause the visible arcing that you're seeing. I am afraid I am not wizard enough to accurately guess the problem. I wonder if the cable TV shield is grounded properly. Even if it is, there are many problems that could cause trouble, including problems with the neighbor's wiring. I'd ask if your neighbors are having trouble.


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## splatz (May 23, 2015)

backstay said:


> I hate to say this but here goes. What if you bonded at your panel? Just to see if your problems go away. Just for "testing purposes. I'm sure somewhere in the building there is already a ground/neutral bond down stream from the service. Very few building I work on don't have some parallel connections. They haven't burned down yet. A clamp on amp meter would tell you.


Hypothetically, can you or anyone suggest the safest possible way to make this test? I have some ideas of my own but I'd be interested in hearing what others would do.


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## HackWork (Oct 2, 2009)

Around here it is VERY common to find every sub panel in an apartment building with the neutral and ground bonded. I'm talking about the panels inside of each unit. It's just the way it is.

So maybe your building is like that. I know you said that it wasn't done in your panel, but maybe the guy who wired your panel knew what he was doing while the guys who wired the other ones didn't. Or maybe your panel was upgraded over the years. There is very little rhyme or reason when it comes to this old stuff.

So maybe what you have is current flowing over the neutral due to too many downstream neutral-ground bonds. That is the first thing that I look for when a customer complains of getting odd shocks or feeling voltage on something.


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## wildleg (Apr 12, 2009)

whether the panels are bonded properly or improperly, I've seen plenty of places that had around 5v neutral to ground, just from inductance on the circuits. I don't see an issue with that.

shielding on the com lines can easily also have induced voltage. 

splitting or connection issues (up the line) would be the most common cause of your hdmi problems.

I would complain to the cable company (if that applies) before trying to move immovable objects.

Alternatively, you could use isolation techniques if your audio/video equipment is that special that is can't work.


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## HackWork (Oct 2, 2009)

Have you checked the cable companies bonding? Usually the demarc is accessible and you should be able to see if it's bonded or possibly bond it yourself.


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## backstay (Feb 3, 2011)

splatz said:


> Hypothetically, can you or anyone suggest the safest possible way to make this test? I have some ideas of my own but I'd be interested in hearing what others would do.


Bonding jumper from ground bar to neutral bar.


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## HackWork (Oct 2, 2009)

backstay said:


> Bonding jumper from ground bar to neutral bar.


That might be dangerous due to a large arc when making the connection. It's best to have an apprentice touch both first to see if there is a lot of potential between those two points.


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## don_resqcapt19 (Jul 18, 2010)

splatz said:


> I doubt that 5v is enough to cause the visible arcing that you're seeing. I am afraid I am not wizard enough to accurately guess the problem. I wonder if the cable TV shield is grounded properly. Even if it is, there are many problems that could cause trouble, including problems with the neighbor's wiring. I'd ask if your neighbors are having trouble.


You can see visible arcing if you short out a D cell battery. Very small voltages can result in a visible arc.


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## don_resqcapt19 (Jul 18, 2010)

wildleg said:


> whether the panels are bonded properly or improperly, I've seen plenty of places that had around 5v neutral to ground, * just from inductance on the circuits*. I don't see an issue with that.
> 
> ....


I don't see how that is possible if the EGC has been installed per the code rules.


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## brian john (Mar 11, 2007)

ewicky said:


> L-N is ~125VAC, which, although higher than I would prefer, seems completely normal.


Why are you bothered by 125 VAC?



> N-G is ~5VAC! This alarmed me. Look around at what other people have measured as "stray voltages" N-G, many people were complaining of potentials of 1 volt or less.


Not sure of your distribution system in your building but assuming you are on a riser system with a main service in a main electric room, it would be quite possible you have a difference of potential between neutral and ground, matter of fact you should have a difference of potential if you did not and the service neutral is bonded some distance away in the Main Service then I would say you have problems, with the neutral being grounded downstream and this still could be an issue depending where the downstream ground is.

Measure current, on the equipment ground conductor (EGC) and on your AV cables. If you have current you have a neutral grounding issue or possible some equipment like a resistive heater, with one element grounded.

Back to the voltage between the EGC and neutral I have seen through wiring errors by the installing electricians 125 VAC between the EGC and neutral and equipment a lot more sensitive than your AV equipment operated fine for months.

Other than that one site I have seen a few other cases had 7-15 VAC in hospitals and data centers and same thing everything was operational no problem



> Theoretically, a N-G potential shouldn't really hurt anything (that I know of) so I didn't think it was that big of a deal. That was, until I received an alarming shock from an RCA cable in my A/V system.


You may have other issues shocking you but 5 VAC ain't giving you an alarming shock



> The maintenance crew for the complex was useless (their $5 receptacle tester said everything was fine)


They are maintenance workers not electricians you are an electrician and you are baffled why shouldn't they be baffled as well?



> I tried unplugging my entire A/V system to rule out the possibility that one of the pieces had fault. The N-G potential did not go away.


And as explained it won't or at least should not


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## telsa (May 22, 2015)

1) Your meter is not capturing the 'problem' which is almost certainly 'high' voltage spikes produced as if they are harmonics. 

2) 5 V is not spark worthy. A DMM will average down a much higher voltage that is extremely brief to read as 5 V.

3) Failing transformers can produce bizarre voltage transforms. As long as the energy involved is low enough they can soldier on this way for the longest time. 

3a) Failing capacitors can also produce bizarre spikes. Again, as long as the energy involved is low enough they can soldier on. These days, capacitors are ten-a-penny in switching power supplies. You should see the monsters inside flat panel TVs.

4) The only gear that can spot such weirdness is an oscilloscope. It makes no attempt at 'averaging' the energy over time. All ordinary meters will blend down spikes, of course. 

This is tic is what has eluded you.

5) The odds, the statistics, say that your problem is being generated by one of your nearby neighbors. She is imposing a spike-waveform every time she turns on her TV. The odds favor it being an older flat panel TV -- one that needs a monster power supply -- and which uses lots of power ~ 220 W or some such. 

But, those are just odds. 

This scenario would explain why your headache comes and goes with the time of the day. 

This is a big 'tell' as to the nature of your blues._ It's being driven by something that gets turned on and off._ Even a defective wall wart does not have that property.

It would also be why nothing that the complex management can do will avail you.

6) Your gear is sensitive to exterior noise because it's hugely based on solid state electronics. These have ultra fast response times. Like an oscilloscope, transistors don't 'average' voltages. They change state at gigahertz speed. 

Your system will buffer// filter the energy coming down the hot.

It will be naked to the world at the chassis ground -- which is commonly used as the DC voltage sink in 'electronics world.' ( You see this a LOT. )

So when clutter comes 'up the pipe' via the neutral it confounds the primitive logic of your low pass filter ( part of every switching power supply ) causing a spiky neutral to bias even the hot. 

( The low pass filter gets its name because it will only pass low frequencies through it -- but it's directional -- it only stops high frequency noise coming in from the hot side. It's naked to %$#@ coming up the neutral// DC ground.)

Now you've got %$#@ filthy power feeding your gear. To a highly tuned ear, 'something's off.' Indeed, transistors are vulnerable to reverse bias voltage spikes. It causes them to let the smoke out.

You may have read that audiophiles are going for old school vacuum tubes.

After all the BS and garble, the real reason for this itch is that vacuum tubes can't possibly respond to ultra brief spikes in either the hot or the neutral. They are inherently buffered by the laws of physics.

Consequently, at the speed of human perception, their output seems positively perfect -- and the 'why' is not understood.

They are automatic noise rejectors. _That's the why_.


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## oliquir (Jan 13, 2011)

use a 120V bulb and put it between hot and ground, if it is normally bright your ground is probably ok, if buld doesnt light up or low intensity then you have a problem.


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## mitch65 (Mar 26, 2015)

how is the humidity in your place? Almost sounds like static arc. Your HDMI, RCA coax jacks are isolated from the power side of the devices. Maybe a humdifier is the answer


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## Big John (May 23, 2010)

Dollars to donuts you have neutral current flowing on your equipment grounds. Get a clamp-on ammeter and hook it around the equipment ground feeding your panel.


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## Nukie Poo (Sep 3, 2012)

If the neutral (anywhere between the main bonding jumper at the service and your sub) is carrying any significant current from normal unbalanced loads, there will be a voltage drop across it. The higher the current, the larger the drop. With a properly grounded, bonded ECG, you will see said voltage drop at the far end of the sub-feeder/panel between the N and EGC.


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## Big John (May 23, 2010)

Nukie, while I agree you will often have N-G VD, he says he's seeing EGC sparking. 
So it sure sounds like he's got current flow where he shouldn't.


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## Nukie Poo (Sep 3, 2012)

Big John said:


> Nukie, while I agree you will often have N-G VD, he says he's seeing EGC sparking.
> So it sure sounds like he's got current flow where he shouldn't.




Didn't catch that part. You are so right: Under no-fault conditions, there should be no current passing through ECG


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## Leehaefele (Sep 17, 2015)

ewicky said:


> I used the forum's search feature but couldn't find good advice.
> I've also tried googling, to no avail. I thought maybe someone here could provide some advice.
> 
> Although I perform electrical work as a trade, I live in an apartment for which I, of course, can't work the electrical system.
> ...





ewicky said:


> I used the forum's search feature but couldn't find good advice.
> I've also tried googling, to no avail. I thought maybe someone here could provide some advice.
> 
> Although I perform electrical work as a trade, I live in an apartment for which I, of course, can't work the electrical system.
> ...


I operate a catv company. CATV wires are bonded to EL Grounding Conductor. Often I get calls from my repair people finding melted cable tv wires. I require them to stop work and call me. Cause: Catv wire is being used as neutral, or as ground and there is a fault. I have found experienced local electricians that do not connect ground to neutral at first device, they think hooking up ground rods only is correct. Now, if you have no N-G connection, surge suppressors will impose some voltage on the ground. I find mobile homes with 120v on chassis frame, which is bonded to metal siding. Many have metal entrance steps! Typical cause is lack of N-G connection and shorted electric water heater element. In one case I am called to a hot trailer, melted CATV wire, local electrician responds, notes that oven light does not work with cable drop disconnected, orders a new oven control and drives a 4’ ground rod which he attaches to a screw on the metal siding. I arrive, find 3 wire 240v service with no N-G connection at the monile Home breaker box. Stove is wired to the ground and only ground path to Neut is the CATV wire. (Stove is 240v, except for oven light) Anyway, there are many homes that do not have correct N-G bonding and of course there can be neutral connection failures.


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## Majewski (Jan 8, 2016)

Leehaefele said:


> I operate a catv company. CATV wires are bonded to EL Grounding Conductor. Often I get calls from my repair people finding melted cable tv wires. I require them to stop work and call me. Cause: Catv wire is being used as neutral, or as ground and there is a fault. I have found experienced local electricians that do not connect ground to neutral at first device, they think hooking up ground rods only is correct. Now, if you have no N-G connection, surge suppressors will impose some voltage on the ground. I find mobile homes with 120v on chassis frame, which is bonded to metal siding. Many have metal entrance steps! Typical cause is lack of N-G connection and shorted electric water heater element. In one case I am called to a hot trailer, melted CATV wire, local electrician responds, notes that oven light does not work with cable drop disconnected, orders a new oven control and drives a 4’ ground rod which he attaches to a screw on the metal siding. I arrive, find 3 wire 240v service with no N-G connection at the monile Home breaker box. Stove is wired to the ground and only ground path to Neut is the CATV wire. (Stove is 240v, except for oven light) Anyway, there are many homes that do not have correct N-G bonding and of course there can be neutral connection failures.


man thats just bad troubleshooting work/skills/ethics when they only order oven parts....


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## mofos be cray (Nov 14, 2016)

Majewski said:


> man thats just bad troubleshooting work/skills/ethics when they only order oven parts....


Should have ordered a microwave, way more efficient for hot dogs.


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## Slay301 (Apr 23, 2018)

5$ says some one cheated on a photo cell only ran a 2 wire and they are using the ground wire


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