# Ghost voltages



## HARRY304E (Sep 15, 2010)

[email protected] said:


> I have a four plex that i wired and I put in 3 way switched outlets in. All the outlets in all four units have a ghost voltage of roughly 70v. Only one unit lights up the ideal plug in tester very dim when the switch is in the off position. Is this common?



Yes if you are using a T-5 1000


You need a low "Z" Voltage meter.


Welcome to the forum..:thumbup::thumbup::thumbup:


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## [email protected] (May 18, 2012)

Do you know why it would light up in one unit and not the other 3 units?


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## HARRY304E (Sep 15, 2010)

[email protected] said:


> Do you know why it would light up in one unit and not the other 3 units?



Because the plug tester is picking up the ghost voltages .


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## Aussielec (Apr 1, 2012)

[email protected] said:


> Do you know why it would light up in one unit and not the other 3 units?


Ghost voltages can be either induced or capacitive voltages..

I'd say you are picking up capacitive voltages in three of the units and an induced voltage in the fourth. Your tester light will not work because with all capacitance voltages there will be no actual current flow...

Induced voltages on the other cause circulating currents to flow, hence when you plug your tester into the fourth outlet it glow's ever so slightly...


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## Lone Crapshooter (Nov 8, 2008)

Ghost voltage have always been there it is because we are using DMM's that we are aware of them.

When I started in this business we were using Triplett or Simpson analog meters. The DMM was reserved for the labs. 
The analog meters had a low input resistance most of them had 20K per volt. With the advent of the DMM came high input resistance. Each meter has its tradeoffs. The analog meter would load a electronic circuit down and not the circuit operate properly. Bad for the techs but electricians were not bothered with ghost voltages. 
DMM with the high input resistance 11 meg ohms per volt will not load circuits but they drive electricians crazy with ghost voltages but they are grate for techs.

A solution might be is to connect a incandesant bulb in a rubber socket to the circuit and measure the voltage across the bulb. If the voltage is zero or extremely low with the bulb in the circuit and then it raises substanicaly with the bulb out of the circuit then you have induced voltage.


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## [email protected] (May 18, 2012)

Thanks! I hope now I have enough info for the inspector to understand too. He wants me to fix it and I said tell me how and I will. Pretty sure you cant get rid of it.


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## Semi-Ret Electrician (Nov 10, 2011)

[email protected] said:


> Thanks! I hope now I have enough info for the inspector to understand too. He wants me to fix it and I said tell me how and I will. Pretty sure you cant get rid of it.


just apply green tape & ground one end of the unused conductors


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## mbednarik (Oct 10, 2011)

you don't have lighted switches do you?


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## RIVETER (Sep 26, 2009)

[email protected] said:


> I have a four plex that i wired and I put in 3 way switched outlets in. All the outlets in all four units have a ghost voltage of roughly 70v. Only one unit lights up the ideal plug in tester very dim when the switch is in the off position. Is this common?


NO, it is not common.


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## [email protected] (May 18, 2012)

no lighted switches. I can also take the power source off and still get the voltage.


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## Semi-Ret Electrician (Nov 10, 2011)

[email protected] said:


> no lighted switches. I can also take the power source off and still get the voltage.


Have you tried any of our suggestions? If so what have you found?


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## [email protected] (May 18, 2012)

I put a wiggy on it and the voltage goes to zero. Any sort of resistance puts the voltage to zero. Im thinking it is inductance from the other hot wires around it.


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## macmikeman (Jan 23, 2007)

[email protected] said:


> I put a wiggy on it and the voltage goes to zero. Any sort of resistance puts the voltage to zero. Im thinking it is inductance from the other hot wires around it.



They make a terrific test unit for that very thing. It's called a "Combination Arc-fault circuit breaker" made by the Cutler-Hammer company in the BR series. You can distinguish it by the almost double length of the breaker compared to regular ones. It works really good at tripping under the conditions of non arcing that you describe..... Cost varies but usually around forty bucks.


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## cayuga (Apr 9, 2012)

Doing a resi rewire and had to pull 8 circuits to the attic. created a chase and used 2 1/2 " PVC through the chase. hooking up the 7th circuit I got a zap checked it and was pulling 19.8 volts. Now here is the kicker. the wire was not hooked up at the other end. not in the box or even stripped yet. shut everything down and ohmed all wires. no shorts. hooked it back up and still had 19.8 volts.


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## Shockdoc (Mar 4, 2010)

You might have prior work stealing the neutral on your circuit with a resistant connection upstream towards the grounding point. You could be reading feed over current feeding thru loads coming back on the hot .


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## [email protected] (May 18, 2012)

Its a homerun to the switch box and feeds from there to the outlets.


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## Semi-Ret Electrician (Nov 10, 2011)

cayuga said:


> Doing a resi rewire and had to pull 8 circuits to the attic. created a chase and used 2 1/2 " PVC through the chase. hooking up the 7th circuit I got a zap checked it and was pulling 19.8 volts. Now here is the kicker. the wire was not hooked up at the other end. not in the box or even stripped yet. shut everything down and ohmed all wires. no shorts. hooked it back up and still had 19.8 volts.


You may have been "zaped" by a wire that had accumulated a capacitive charge from the nest of charged wires. Even disconnected transmission lines see this and have to be discharged. Once discharged, the affects of leakage, inductance and capacitance started to return, but as you know, were not dangerous.

As I said earlier, apply some green tape and ground one end, of the unused wires, to the supply side ground bus. And quit using a high Z meter on electrical circuits.


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## McClary’s Electrical (Feb 21, 2009)

Lay out 100' of 12/3 and put power on the black and use the white as a grounded conductor. Now go to the other end of the wire and read voltage between red and ground. You'll see the same thing you're describing.


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## LARMGUY (Aug 22, 2010)

Lots of good info fellas. :thumbsup:


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## brian john (Mar 11, 2007)

mcclary's electrical said:


> Lay out 100' of 12/3 and put power on the black and use the white as a grounded conductor. Now go to the other end of the wire and read voltage between red and ground. You'll see the same thing you're describing.


Been there done that as a demonstration for an inspector that would not pass a job due to ghost/phantom voltages on a switched outlet.


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