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Old 10-31-2011, 06:14 PM   #1
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I have a light circuit controlled by 2 three way switches. With no light in the circuit I have about 30 volts between the neutral wire and the hot leg coming back from the 3 way switch, when the switches are in the off position. But you can touch these wires together without getting a spark, you can touch these wires and cannot feel anything. With one switch in the on position you get 120 volts, turn that one off and you get the 30 volts, turn the other switch on and you get 120 volts, off you get the 30 volts But you can hook a drop light on to the wires and the 30 volts goes away, and the light works when you turn either switch to the on position. I have checked the voltage with a digital meter, which shows the 30 volts and with a cheaper analog meter which also shows the voltage, but with an older Triplett analog meter there is not voltage reading in the off position, and 120 volts in the on position. Can this be induced voltage from the traveller legs or a leaking switch or something else???? thanks in advance for any help.......

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Old 10-31-2011, 06:51 PM   #2
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First testing for voltage with your fingers can have deadly consequences and should never be done.

What you were seeing is called phantom voltage. As you found out it goes away once a load like a lightbulb is applied to the circuit. The wiggy has enough load to cancel out the reading that digital meters do not.

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Old 10-31-2011, 07:23 PM   #3
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This website needs a department for three way switches all by itself.
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Old 10-31-2011, 07:28 PM   #4
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This website needs a department for three way switches all by itself.
And sub panels.
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Old 10-31-2011, 07:33 PM   #5
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Hay 35ga, You must be a thin dude, (or dudette)!
I've seen the same thing in an older house with no 3 way involved. Had the power off and still got a low voltage reading, about 25 volts when I verified power was off to work on it. A long time Rehaber that I know said the some thing, phantom voltage. It still made me nervous.
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Old 11-01-2011, 11:58 AM   #6
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I thought the problem was a phantom or ghost voltage but wanted some more thoughts to go with mine. I never check voltage with my fingers unless I have thoroughly checked it with at least 2 meters first. And with the power off, there was no continuity between the 2 wires so I checked it by touching the 2 wires together with the power on and nothing. I have wired alot of 3 way switches before and never had any problem, but the homeowner decided to check the last circuit and it showed voltage on his digital meter and he automatically determined that something was wrong. (and I don't blame him at all). Live and learn!!!!
No I am not a thin dude, I am a fat old retired man
Thanks to everyone for the added information and support.
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Old 11-01-2011, 10:13 PM   #7
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Sometimes if you connect a 2000 ohm headset through a diode you can hear a local radio station on a wire with a phantom voltage.

In the good old days, this was how crystal sets worked.
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Old 11-01-2011, 10:21 PM   #8
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Hay 35ga, You must be a thin dude, (or dudette)!
I've seen the same thing in an older house with no 3 way involved. Had the power off and still got a low voltage reading, about 25 volts when I verified power was off to work on it. A long time Rehaber that I know said the some thing, phantom voltage. It still made me nervous.
Don't worry about Phantom voltage. It is caused by using the wrong meter. If the breaker is off, and use the proper equipment to test for voltage, vs. a off the shelf multi-meter, that is not for testing voltage, you are going to read it.

The proper equipment to have in your bag should be the following: A No Touch to check for any live lines, so you can try to find out when it is possibly dead, when turning off a breaker. A Sperry 80 or Amprobe Ac/Dc tester to check if voltage is on the circuit. If you want to take it a step up, get a Ideal Vol-Con (runs about $40.00). Yes it is nice to have a DVM, but it does not help when you do stuff as an electrician wold do it. They only use DVM's for certain circumstances, and not to test for voltage or continuity. At least that is in my case.
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Old 11-02-2011, 01:01 PM   #9
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[quote=gregzoll;761932]Don't worry about Phantom voltage. It is caused by using the wrong meter. If the breaker is off, and use the proper equipment to test for voltage, vs. a off the shelf multi-meter, that is not for testing voltage, you are going to read it.

The proper equipment to have in your bag should be the following: A No Touch to check for any live lines, so you can try to find out when it is possibly dead, when turning off a breaker. A Sperry 80 or Amprobe Ac/Dc tester to check if voltage is on the circuit. If you want to take it a step up, get a Ideal Vol-Con (runs about $40.00). Yes it is nice to have a DVM, but it does not help when you do stuff as an electrician wold do it. They only use DVM's for certain circumstances, and not to test for voltage or continuity. At least that is in my case.

I always carry an old Triplett meter, it is probably 30 years old, most likely before digital meters were ever thought of. It showed no voltage with the switches in the off position. The homeowner also had a analog meter, ( a newer multimeter, and most likely a lot cheaper than I paid for the Triplett) His meter showed voltage, so I got my Fluke meter, digital, and it showed voltage. so he thought my Triplett was wrong, and even after I put a light in the circuit and the voltage went away, he was still unconvinced that it was ghost voltage, then he started wanting to run all new wire for the entire circuit. I have finally convinced him of what we were seeing, but it took me over a week to prove it to him. The only reason I even have a digital meter is when I worked in maintenance we might get a spike or voltage that only appeared for a split second, and the old analog meter would not show it. thanks to everyone, hopefully I learned something and the homeowner is happy. (after all this was a freebie cause it is my next door neighbor)

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