# "Phantom voltages"



## furbis (Jan 23, 2007)

I have a GB ticktracer that gives me a tone on a regular basis when there is not enough voltage on the wire to read on my wiggy, on the other hand this trait came in real handy this last week on a house we are trimming when the homeowner gave me the general areas on the wall where there should have been a recepticle and a switch, most circuits in the house were hot and I found the covered boxes by running the tictracer over the drywall, pretty slick I thought.


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## MDShunk (Jan 7, 2007)

I use a 2' level to find the "bulge" where buried boxes are. This doesn't work for skim coated veneer plaster walls, because they make it all flat. I have dreams and fantasies of finding buried boxes with a 10lb. sledgehammer. :jester:


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## furbis (Jan 23, 2007)

I have dreams and fantasies of finding buried boxes with a 10lb. sledgehammer.


you and me both buckaroo, we did use a straight edge to help confirm the location of the buried boxes.

in another room of the house we had a recepticle and light in the closet that did not work and we thought there was another buried box but it ended up being a cut romex, (looked like they got it with the &^%*$# rotozip) so I saved the length of romex for the homeowner to show the drywallers and proceeded to cut holes in the nicely painted walls with very little worry to refeed the closet.


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## MDShunk (Jan 7, 2007)

Furbis, I feel your pain.


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## Louieb (Mar 19, 2007)

Back in the old days when Electricians controlled the job,a 3/4 emt bender worked great....


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## Current (Jul 4, 2011)

A few volts doesn't bother me, I hate when I read 120V on a dead wire. Hopefully with my new Milwaukee tester with LoZ to replace my Fluke T5 I won't have this issue anymore. Now all I need is a chance to use it in the field :thumbup:


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## micromind (Aug 11, 2007)

While phantom voltages on circuits of less that 600 volts are an annoyance, they can be lethal on overhead power lines. I've seen arcs several inches long when grounding de-energized open-circuit overhead conductors. They make a nice SNAP that I wouldn't want to be a part of!!


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## RIVETER (Sep 26, 2009)

MDShunk said:


> Ever measure a few volts on a cable or wire with your digital multimeter, and the cable or wire was really "dead". Ever wondered why? This bulletin from NEMA explains the so called 'phantom voltage' or 'ghost voltage'.
> 
> http://www.nema.org/stds/eng-bulletins/upload/Bulletin-88.pdf


I personally don't believe in phantom voltages. "PHANTOM" indicates that there is no reason for it to be there. From the web reference you posted it said that an improper use of a high impedance meter could cause the reading. The purpose of using a Hi Impedance meter is so that the meter, itself, doesn't create a "LOADING" effect. Maybe they just misspoke.


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## Current (Jul 4, 2011)

RIVETER said:


> I personally don't believe in phantom voltages. "PHANTOM" indicates that there is no reason for it to be there. From the web reference you posted it said that an improper use of a high impedance meter could cause the reading. The purpose of using a Hi Impedance meter is so that the meter, itself, doesn't create a "LOADING" effect. Maybe they just misspoke.


When dealing with some electronics or control circuits you don't want that loading effect. But when dealing with power you do want it in order to dissipate the ghost voltage.


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## Big John (May 23, 2010)

RIVETER said:


> I personally don't believe in phantom voltages. "PHANTOM" indicates that there is no reason for it to be there....


 It's just a name. You ever call a phase conductor the "hot"? It's not actually heated up, is it?

The only folks who find terms like "phantom" and "ghost" voltage confusing are customers. And they would find it just as confusing if we started talking about "induced voltage".

-John


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## RIVETER (Sep 26, 2009)

Current said:


> When dealing with some electronics or control circuits you don't want that loading effect. But when dealing with power you do want it in order to dissipate the ghost voltage.


How does the meter do that? And, what happens when the meter is removed? The voltage will still be there...right? I am not saying that I know...I am just asking.


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## drsparky (Nov 13, 2008)

I would apply the Copenhagen interpretation to this question.


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## walkerj (May 13, 2007)

RIVETER said:


> How does the meter do that? And, what happens when the meter is removed? The voltage will still be there...right? I am not saying that I know...I am just asking.


There is no voltage:thumbsup:


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## Current (Jul 4, 2011)

walkerj said:


> There is no voltage:thumbsup:


There actually is voltage via capacitive coupling when using a hi impedance meter.


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## macmikeman (Jan 23, 2007)

There is no voltage when I put my knopp on the wires, or if there is, then I turn off the circuit breaker and test again.......


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## drsparky (Nov 13, 2008)

By observing an object you effect the object. A low impedance meter will load a circuit a high impedance circuit can give you "unexpected" readings. If you think of it as a voltage divider even the "unexpected" makes sense.


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## Big John (May 23, 2010)

drsparky said:


> By observing an object you effect the object....


 Professor Heisenberg, is that you?

-John


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## RIVETER (Sep 26, 2009)

walkerj said:


> There is no voltage:thumbsup:


Are you saying that is is a "PHANTOM"?


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## RIVETER (Sep 26, 2009)

I want to say that this is a great post from MDShunk. It a is very misunderstood subject and should be discussed a lot.


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## drsparky (Nov 13, 2008)

Big John said:


> Professor Heisenberg, is that you?
> 
> -John


Heisenberg is hard to understand, Gribbin _(In Search of Schordinger's Cat)_ made it easier for simple minds like mine.


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## B4T (Feb 10, 2009)

Maybe the" phantom voltage" found a new home since this thread is over (4) years old..


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## RIVETER (Sep 26, 2009)

Big John said:


> It's just a name. You ever call a phase conductor the "hot"? It's not actually heated up, is it?
> 
> The only folks who find terms like "phantom" and "ghost" voltage confusing are customers. And they would find it just as confusing if we started talking about "induced voltage".
> 
> -John


Maybe so, but just today I was listening to an experienced journeyman call an Ungrounded System as one with a floating neutral. There will be no voltage...at all, unless there is a difference of potential. If there is a difference of potential...and it is indicated on a meter...there is current flow.


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## Current (Jul 4, 2011)

B4T said:


> Maybe the" phantom voltage" found a new home since this thread is over (4) years old..


I had no idea.


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## RIVETER (Sep 26, 2009)

Current said:


> I had no idea.


I didn't know, as well, but it is still a good thread. A lot of people don't really understand and it is good to talk about it.


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## Big John (May 23, 2010)

RIVETER said:


> Maybe so, but just today I was listening to an experienced journeyman call an Ungrounded System as one with a floating neutral. There will be no voltage...at all, unless there is a difference of potential. If there is a difference of potential...and it is indicated on a meter...there is current flow.


The thing to remember with phantom voltage is that there actually will be current flow. It will be in the microamp range, and all but undetectable to us, but you're right: If there's potential, and the circuit is completed, there will be current.

Not sure how the floating neutral plays into this? 

-John


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## Wirenuting (Sep 12, 2010)

drsparky said:


> Heisenberg is hard to understand, Gribbin (In Search of Schordinger's Cat) made it easier for simple minds like mine.


Oh man, there is Schordinger's cat again. 

Phantom voltage is caused by an electrical phenomena. 

Any unexplained outage is caused by an electrical phenomena. 

Floating grounds are caused by the darn cat not being looked at.


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## B4T (Feb 10, 2009)

Current said:


> I had no idea.


Funny how the re-tread gets more mileage than the original..

Must be a better bunch of people to kick it around.. :thumbup:


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## RIVETER (Sep 26, 2009)

Big John said:


> The thing to remember with phantom voltage is that there actually will be current flow. It will be in the microamp range, and all but undetectable to us, but you're right: If there's potential, and the circuit is completed, there will be current.
> 
> Not sure how the floating neutral plays into this?
> 
> -John


Thanks for the post. I, as well, don't really know how people come up with a floating neutral concept. If you know that there should be no reading from a phase conductor to ground with a meter, and you get one...they seem to want to call it PHANTOM, which, somehow legitimizes it and we just go back to work. If, in an electrical system, you don't intentionally install a PHANTOM neutral, then there should be none. Where are our engineers on this forum?


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## Big John (May 23, 2010)

I think we may be talking about two different things, though they are related:

When you have a system where the neutral is not intentionally grounded, and you measure from line to ground, you will get a voltage reading. This is because of imperfect insulation in the system and capacitive coupling to ground. It's usually not called "phantom voltage" (not that I've ever heard, at least).

When you have a wire that is de-energized for all intensive purposes, but it is run near energized conductors, it can get voltage induced in it (also through capacitive coupling). If you put any kind of load on it, the voltage will drop because it's only capable of sourcing a few microamps. This is the phenomenon called "phantom" or "ghost" voltage.

-John


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## danickstr (Mar 21, 2010)

I always understood it as if the flow of electricity through a wire creates a donut-like field that moves down the wire. the wires close to the live wire are energized, in a way similar to a transformer. I always see it on travelers if I am toning out a 3-way that got its wires crossed.


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## Bill1 (Jul 18, 2011)

Big John said:


> I think we may be talking about two different things, though they are related:
> 
> When you have a system where the neutral is not intentionally grounded, and you measure from line to ground, you will get a voltage reading. This is because of imperfect insulation in the system and capacitive coupling to ground. It's usually not called "phantom voltage" (not that I've ever heard, at least).
> 
> ...


Is this the same as an "eddy current"?


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## kaboler (Dec 1, 2010)

how do I know if my multimeter is high or low impedance?


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## brian john (Mar 11, 2007)

kaboler said:


> how do I know if my multimeter is high or low impedance?


Google it.


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## macmikeman (Jan 23, 2007)

Here is my highly scientific theory..... Use a solenoid based voltage tester and the phantoms do really go away to phantomville. Course it is not exactly an accurate way to see exactly what the true voltage reading is, but shoot, most times the kids video console doesn't care that much about tight tolerances..


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## eutecticalloy (Dec 12, 2010)

Bill1 said:


> Is this the same as an "eddy current"?


No, eddy current are small circular current induced in the core of a transformer.


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## eutecticalloy (Dec 12, 2010)

danickstr said:


> I always understood it as if the flow of electricity through a wire creates a donut-like field that moves down the wire. the wires close to the live wire are energized, in a way similar to a transformer. I always see it on travelers if I am toning out a 3-way that got its wires crossed.


Yes, induction, but like most have been saying the induction or capacitive coupling isn't capable of carry much current. You could sit there and short the two together and nothing would happen. It's just annoying.


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