conundrum -- Induced voltage in 14 g romex

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ajohnvoyager

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Today, I connected black wire of 14g romex to black wire of 120 AC 12 g romex. Checked other end of 14g romex with voltage tester and, of course the voltage tester went off. Then I happened to put voltage tester against the free white wire of 14g romex and it went off. I separated the white wire widely from the black wire and it still went off. Then I took a VOM and tested the black and white wire. The black was 120v as expected but the white registered a 60v! The white wire is not connected to anything at either end. More specifically the voltage drop from both the black 14 g romex wire and the white wire is measured to a ground wire in the wall. I have also check the resistance between the two wires in the 14 g romex and there is no continuity (infinite resistance).

Anyone have any explanations. BTW, the 14 g romex is not coiled and this test piece is only three feet.
 
That is amazing. That your "join date" says oct 2003, but you only have 5 posts... Your "post-o-meter" must have hit a million, and flipped!!!! As for the conundrum.... That sounds like a wild phenomenon. Very interesting in fact. I think if I were in your shoes, the next thing I would do, is check for voltage between the "ground wire" in the wall.... and the actual ground... as in Earth. Like stick one lead of your meter in the dirt and the other in your wall ground. I hope to hear the results!

best wishes!
FREQ;)
 
ajohn@voyager.net said:
Today, I connected black wire of 14g romex to black wire of 120 AC 12 g romex. Checked other end of 14g romex with voltage tester and, of course the voltage tester went off. Then I happened to put voltage tester against the free white wire of 14g romex and it went off. I separated the white wire widely from the black wire and it still went off. Then I took a VOM and tested the black and white wire. The black was 120v as expected but the white registered a 60v! The white wire is not connected to anything at either end. More specifically the voltage drop from both the black 14 g romex wire and the white wire is measured to a ground wire in the wall. I have also check the resistance between the two wires in the 14 g romex and there is no continuity (infinite resistance).

Anyone have any explanations. BTW, the 14 g romex is not coiled and this test piece is only three feet.
Click to expand...

I know you aren't going to like my answer, but it is simple and true.

You don't know how to use your test equipment.

Sorry for being so brash, but I wouldn't think much at all about those readings since they were taken with a cheep tracer and a high impedance DVOM.

Grab a wiggy or a vol-con and re-test.
 
CONTROL FREQ said:
That is amazing. That your "join date" says oct 2003, but you only have 5 posts... Your "post-o-meter" must have hit a million, and flipped!!!! As for the conundrum.... That sounds like a wild phenomenon. Very interesting in fact. I think if I were in your shoes, the next thing I would do, is check for voltage between the "ground wire" in the wall.... and the actual ground... as in Earth. Like stick one lead of your meter in the dirt and the other in your wall ground. I hope to hear the results!

best wishes!
FREQ;)
Click to expand...

And you only have 38 since January???

Heck, I have done that in a week.

:D
 
conundrum

conundrum

I can't comment upon my post-o-meter, but I did run the test that you asked. I took an extension cord and "plugged" it into the ground -- yes -- earth. I then again tested the black wire and it registered 122v. So I knew that my earth setup was good. Again the white wire tested 60v. The voltage drop between the house ground and the earth ground was 44mv (millivolts not volts). I have not made a mistake on the order of magnitude of the white wire. It is volts. I have to reiterate that the white wire in the three foot test piece is not connected to anything.
Thanks
-- Bob Johnson
 
Conundrum

Conundrum

K8MHZ said:
I know you aren't going to like my answer, but it is simple and true.

You don't know how to use your test equipment.

Sorry for being so brash, but I wouldn't think much at all about those readings since they were taken with a cheep tracer and a high impedance DVOM.

Grab a wiggy or a vol-con and re-test.
Click to expand...

No, I don't take offense at all. I do use this DVOM all the time, but it was purchased at Lowes a number of years ago. What put me on to the problem was the tracer, that in my experience does not go off on the neutral side of a wire. Hence my measurements. But, thank you.

-- Bob Johnson
 
K8MHZ said:
And you only have 38 since January???

Heck, I have done that in a week.

:D
Click to expand...

How can I get mine to say I joined in 1966, and have made over one billion? :D (I do enjoy your posts!) I usually type so slow it kicks me off or somebody else writes what I was gonna say... It all works out well in the end!:lol:
 
ajohn@voyager.net said:
No, I don't take offense at all. I do use this DVOM all the time, but it was purchased at Lowes a number of years ago. What put me on to the problem was the tracer, that in my experience does not go off on the neutral side of a wire. Hence my measurements. But, thank you.

-- Bob Johnson
Click to expand...

Your tick tracer reads by looking at capacitive coupling. That means that it is an almost infinite impedance device.

Your DVOM is a very high impedance device, I'm thinking around 100 thousand ohms or more.

In a nutshell, that means you can't trust them. Since the circuit you are looking at is not loaded, any differential, no matter how current limited, will be detected.

Just placing two wire near each other will make a high impedance device indicate that a voltage is present.

A solenoid tester, like a Wiggy or a Vol-Con will place a load on the circuit and then read the voltage. They are low impedance testers and are much better at indicating 'real' voltage. The voltage you are seeing with your tracer and DVOM, if not confirmed by a low impedance tester is sometimes referred to as 'ghost voltage'.

Also, some tick tracers are better than others. My fave is my Greenlee. The worst was the red one I had, GB perhaps?

Take your tick tracer out to a large power line. All you have to do is get under a 138 or 345kV line with your tick tracer on and it will indicate without touching anything at all.
 
ajohn@voyager.net said:
I can't comment upon my post-o-meter, but I did run the test that you asked. I took an extension cord and "plugged" it into the ground -- yes -- earth. I then again tested the black wire and it registered 122v. So I knew that my earth setup was good. Again the white wire tested 60v. The voltage drop between the house ground and the earth ground was 44mv (millivolts not volts). I have not made a mistake on the order of magnitude of the white wire. It is volts. I have to reiterate that the white wire in the three foot test piece is not connected to anything.
Thanks
-- Bob Johnson
Click to expand...

That IS interesting. I'll wait for somebody much smarter than me to give advice about what you should do next.
 
ajohn@voyager.net said:
What put me on to the problem was the tracer, that in my experience does not go off on the neutral side of a wire. Hence my measurements. But, thank you.
Click to expand...

What problem? :?

If the wire is not connected to earth or a load, it will have an easy time accepting induced voltage. What is catching you by surprise? Why are you doing this?
 
K8MHZ said:
Ancient Chinese secret.

Plus, it helps if your were born before 1966.....

:cool:
Click to expand...

I remember the woolite commercials! That has to count for something... Had an old guy tell me once, (when I was in school) that if you could stretch a big enough piece of copper wire under HT wires... You could get free (stolen) power from the utilities. This was probably 20 years ago, and he said, "IT'S THE SAME AS IF I CARRY A FLOURESCENT BULB OUT THERE...IT'LL LIGHT UP!!!". I never really put any thought into it, but now I hear people talking about cellphone chargers that work off of radio waves... SORRY if I'm 'off-topic' OR AM I?:blink:
 
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George Stolz said:
What problem? :?

If the wire is not connected to earth or a load, it will have an easy time accepting induced voltage. What is catching you by surprise? Why are you doing this?
Click to expand...

Watch out Bob, he's got a virtual hammer! I think your making him mad! HILLARIOUS! Next he'll be telling you to stick your tes
 
CONTROL FREQ said:
I remember the woolite commercials! That has to count for something... Had an old guy tell me once, (when I was in school) that if you could stretch a big enough piece of copper wire under HT wires... You could get free (stolen) power from the utilities. This was probably 20 years ago, and he said, "IT'S THE SAME AS IF I CARRY A FLOURESCENT BULD OUT THERE...IT'LL LIGHT UP!!!". I never really put any thought into it, but now I here people talking about cellphone chargers that work off of radio waves... SORRY if I'm 'off-topic' OR AM I?:blink:
Click to expand...

Not really off topic, but bears some explanation.

First, I doubt a 345 kV line would light up a tube from the 100 feet or so you would be away from the conductors. I have worked on seal presses that used RF and would light up a tube up to about 3 feet away.

The new charging pads don't work of radio waves. A compatible device will have one half of a transformer in it and the pad has the other. Just put the device on the pad and now there is a complete transformer.

As for stringing a copper wire far enough, how do you get to the ends? With more wire going back the same way, pretty much cancelling out any induced current. Besides, take a look up to the top of the towers, that wire is already there. The ground wire runs right along with the rest of them and you can walk right up to the metal tower it's connected to and touch it without getting a shock.

Presenting a voltage on a conductor is not the same as providing for current. Just because the difference between one end of a wire and the other is 120 volts, that doesn't mean you can run 120 volt appliances off of it.

For instance, your land line telephone has about 45 volts on it if not ringing. 90 or so when ringing. If you put a 3:1 transformer across the phone lines, you will get 130 volts on the secondary when measured with a DVOM. Now, try to light up a light bulb with it. The bulb will not light because the current is limited.

Try to start a car with a 12 VDC wall wart. Same thing, current limitation. Yep, the DVOM reads 12 volts just like it would across the car battery, but not enough current to do the job.

If you take two pieces of wire and string them up in the air on a dry windy day, hundreds of volts of potential will occur between the two wires. (This happens on dipole radio antennas, causing static and sometimes damaging sensitive receivers), but there is never enough current there to do any amount of work, or we would be using the technique to harness wind power.

There is some current that travels through the earth due to the HV lines. It's fault current and the POCOs are supposed to keep it to a minimum since it makes cows act funny. But with enough distance between ground rods and ideal conditions, actual current bearing voltages may exist and may be enough to light up a light or something. Until the fault is fixed, anyway.

Trust me, if there was any truth to fluorescent tubes lighting up without wires under power lines, I would have taped them to poles and trees when I was a kid so I could find my way home after dark.

My dirt bike didn't have lights.
 
Conundrum

Conundrum

George Stolz said:
What problem? :?

If the wire is not connected to earth or a load, it will have an easy time accepting induced voltage. What is catching you by surprise? Why are you doing this?
Click to expand...

I think that is what I wanted to know. I appreciate your experience.

I did it because I never ran into this phenomenon before. I thought others just might be interested. My memory of Faraday's laws was that something had to move or change. Of course, this is AC so the EMF, with the emphasis on the "M" is changing, so I suppose that I should not be surprised at an induced current. I am surprised at the magnitude of the voltage and that its value is half of the incoming voltage.

Thanks

-- Bob Johnson
 
K8MHZ said:
Not really off topic, but bears some explanation.

First, I doubt a 345 kV line would light up a tube from the 100 feet or so you would be away from the conductors. I have worked on seal presses that used RF and would light up a tube up to about 3 feet away.

The new charging pads don't work of radio waves. A compatible device will have one half of a transformer in it and the pad has the other. Just put the device on the pad and now there is a complete transformer.

As for stringing a copper wire far enough, how do you get to the ends? With more wire going back the same way, pretty much cancelling out any induced current. Besides, take a look up to the top of the towers, that wire is already there. The ground wire runs right along with the rest of them and you can walk right up to the metal tower it's connected to and touch it without getting a shock.

Presenting a voltage on a conductor is not the same as providing for current. Just because the difference between one end of a wire and the other is 120 volts, that doesn't mean you can run 120 volt appliances off of it.

For instance, your land line telephone has about 45 volts on it if not ringing. 90 or so when ringing. If you put a 3:1 transformer across the phone lines, you will get 130 volts on the secondary when measured with a DVOM. Now, try to light up a light bulb with it. The bulb will not light because the current is limited.

Try to start a car with a 12 VDC wall wart. Same thing, current limitation. Yep, the DVOM reads 12 volts just like it would across the car battery, but not enough current to do the job.

If you take two pieces of wire and string them up in the air on a dry windy day, hundreds of volts of potential will occur between the two wires. (This happens on dipole radio antennas, causing static and sometimes damaging sensitive receivers), but there is never enough current there to do any amount of work, or we would be using the technique to harness wind power.

There is some current that travels through the earth due to the HV lines. It's fault current and the POCOs are supposed to keep it to a minimum since it makes cows act funny. But with enough distance between ground rods and ideal conditions, actual current bearing voltages may exist and may be enough to light up a light or something. Until the fault is fixed, anyway.

Trust me, if there was any truth to fluorescent tubes lighting up without wires under power lines, I would have taped them to poles and trees when I was a kid so I could find my way home after dark.

My dirt bike didn't have lights.
Click to expand...

I hope you spelled all that right, cause I just copy/pasted it to a word doc... I WILL use it later I'm sure. Now I know how those charging pads work, but I was actually referring to an article I read about Tesla 'paving the way' (which I have pretty much come to believe) and Edison 'stealing the spotlight'. The article/opinion stated that radio waves could charge a cellphone anytime it wasn't in use; if you were in a populous region (which I tend to avoid). PS I had the same problem with my RM 80, my big brother was the "Jr." so he got the CR 250 I always wanted. Poor me...:cry: That little suzuki did just fine for me though:happyyes:!!!
 
CONTROL FREQ said:
I hope you spelled all that right, cause I just copy/pasted it to a word doc... I WILL use it later I'm sure. Now I know how those charging pads work, but I was actually referring to an article I read about Tesla 'paving the way' (which I have pretty much come to believe) and Edison 'stealing the spotlight'. The article/opinion stated that radio waves could charge a cellphone anytime it wasn't in use; if you were in a populous region (which I tend to avoid). PS I had the same problem with my RM 80, my big brother was the "Jr." so he got the CR 250 I always wanted. Poor me...:cry: That little suzuki did just fine for me though:happyyes:!!!
Click to expand...

I'll try to keep this on topic, but since you brought up Tesla.......

In 2006, on the 150th anniversary of Tesla's birth, my voice was heard in Serbia (actually it was 'Serbia and Montengro') on a radio. The transmission was made from my house in Michigan to Tesla's birthplace. The contact was made from my home made antenna in my back yard to the receiving station's antenna in Serbia. There was nothing else in the mix. No satellites, no repeaters, no Internet, nothing but antenna to antenna. I have a post card from the station in Serbia, YT0TESLA, with the exact date and time it happened on it as proof.

How much power do you think I had to move from Michigan to Serbia in order to get a readable voice contact? Now think about this, I am shooting from a 36 foot piece of wire not as thick as a pencil to a similar target in Serbia. As the energy leaves my antenna, it disperses in a semi-spherical pattern and is diluted in power as it leaves my station. That energy is scattered all over the world, literally. Some of that energy will hit a target less than a pencil thick and 36 feet wide in Serbia. The rest is wasted. Well, unless other people listening enjoyed hearing us talk, that is.

A readable signal in the mode I was using takes about 10 microvolts at the receiving station. A perfect signal, or 'S9', is supposed to be 50 microvolts.

So, in order to be readable I had to put enough energy into my antenna to get 10 microvolts to Serbia without a wired connection.

My radio, an Icom IC-735, puts out 100 watts continuous wave. Since we were using single sideband suppressed carrier, my voice peaks were only at the 40 watt level. My antenna was tuned to match the radio at 50 ohms. That works out to about 45 volts. That 45 volts was detected thousands of miles away in Serbia.

Fortunately, the station in Serbia was a bit like a tick tracer. Neither the tick tracer or the Serbian station used up any of the energy they detected from either the Romex wire or my wire antenna. They just detected it's presence.

To illustrate, one could take a piece of Romex a couple hundred feet long and connect it to a 120 volt power source and have a switch. At the other end a person could hold a tick tracer on it so when the switch was on, the tracer would indicate. Off, it would not. Using Morse Code an understandable message could be sent to the tick tracer and virtually no power would be consumed. This method could be used every day for years and never register on a power meter (watt hour meter).

The same could be done with a DVOM, watching the display change from 0 to 120 volts for the dots and dashes, but SOME power would be used since it does have a measurable impedance of about 100 thousand ohms. Using a DVOM wouldn't use much power, but over many hours of use would register on a power meter.

The same could be done with a light bulb to see when the switch was on or off. But as one would imagine, many hours of use will use up a substantial amount of power.

OK, so we have three different ways to detect voltage on our little telegraph.

What would happen if we put a 10 thousand ohm resistor somewhere in the wire?

Well, the light bulb wouldn't light, that's for sure. But neither the DVOM nor the tick tracer would be affected. Both would indicate that there was 120 volts turning on and off in code.

What about a 200 thousand ohm resistor?

Well, the bulb wouldn't work and the DVOM would read about 60 volts. The tick tracer would indicate just as it always has.

How about a million ohm resistor?

No bulb, no DVOM reading, but the tick tracer would still indicate that there was 120 volts present. Think about it.....how many ohms is insulation??????

THIS is why you need to know what your test equipment is actually indicating!!!

And, I include the light bulb as a piece of test equipment.

Ever heard of a 'test light'?

Yep, I have a 120 volt test light and it has been one of the best pieces of test equipment I have ever owned.
 
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110820-2210 EDT

ajohn@voyager.net:

What you are observing is capacitive coupling from the black hot wire (120 V relative to earth, and neutral) to the floating white wire. This capacitance is about 20 to 30 or so pfd per foot. Then from the white wire to the EGC wire in the Romex is additional capacitance. This produces a capacitive voltage divider. If you truly had a very high impedance meter, then those two capacitors would determine the measured voltage to earth. A typical Digital meter like a Fluke 27 has an input impedance of 10 megohms in parallel with upwards of 100 pfd. Thus, it becomes a major factor in calculating the measured voltage.

Make your Romex longer and the voltage of the white wire relative to earth should be greater.

Go study some electrical circuit theory and see if you can get a better understanding of what is going on.

.
 
K8MHZ said:
Not really off topic, but bears some explanation.

First, I doubt a 345 kV line would light up a tube from the 100 feet or so you would be away from the conductors.
Click to expand...

The theory is true

electromagnetic-fluorescent-bulb-light.jpg
 
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