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 DIY Chatroom Home Improvement Forum Residual Voltage, how much is too much?
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01-20-2013, 05:23 PM   #1
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## Residual Voltage, how much is too much?

In trying to eliminate a light switch, I picked up on a problem. In two wires, that I know are going directly from a 4 way switch to a 3 way switch, I pick up 44 volts in one (wire to ground) and 20 volts in the other (wire to ground). That is with both ends of each wire totally disconeccted. How much voltage is too much? It is obviously picking up voltage from somewhere. Can I use one of these wires to connect the switches?

Thanks for the help!

01-20-2013, 05:34 PM   #2
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What type of meter are you using? What you are seeing is most likely "phantom" or induced voltage due to open-circuit conditions. It is not indicative of a problem (or doesn't sound like it anyway) in your case.

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 01-20-2013, 06:20 PM #3 Newbie   Join Date: Jan 2013 Posts: 3 Rewards Points: 10 Big Jimmy: Thanks for the Reply. What is phantom voltage? I have never heard of it? I have a fluke 87 meter, have checked other outlets, batteries are good, etc. I am trying to eliminate a 4 way switch, because i need the switch for something else. Power goes first to the lights, then to a 3 way, to a 4 way, to a 3 way, and back to my panel. When i took the 4 way out, I had 85 volts on one leg coming from 3 way switch #1. With everything unhooked, I have continuity on the two wires going from switch #1 (3 way) to switch #2 (4 way). but when measuring voltage on either end of the wires, I get 44 volts on one wire and 20 volts on the other. I was assuming there was something crossed/miswired somewhere. Also, if i totally jump out the lights with an extension cord (hot on number 1 to return on number 3) the lights come on and seem to be a bit brighter. Thanks again for the help!
 01-20-2013, 06:26 PM #4 Newbie   Join Date: Jan 2013 Posts: 3 Rewards Points: 10 Correction, sorry. Last line I meant when I jump out the switches.
01-20-2013, 06:56 PM   #5
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Quote:
 Originally Posted by ZackRB42 Big Jimmy: What is phantom voltage? I have never heard of it?
In your case, when you have a conductor in close proximity to another
it will pick up via capacitive induction, some of that power.
Now the currents are usually very small, and with almost no load on it
(such as a digital multi meter) then you will read voltage.
But put any decent load on it (test lamp / anologue meter)
then it will quickly drop off.
In short phantom voltage is usually high in volts but low in amps.
Disconcerting but not usually dangerous.

"phantom - man who cannot die, ghost who walks"

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