Where is this Mysterious AC Voltage Coming from?


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Old 06-01-15, 06:07 PM
Q
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Where is this Mysterious AC Voltage Coming from?

On our utility room sink basin:

I believe it is made of ceramic-coated metal, sits on top of a metal stand and is drained via PVC pipe. The metal stand is on top of dry linoleum flooring - both the sink and the stand are stand-alone and definitely NOT touching anything else surrounding them, including the faucet that comes out of the wall (which has 0vac to ground).

Here's what I do know:
From house ground to the metal sink drain I read a steady 45vac.
From house ground to the metal stand I read a steady 52vac.
From house "hot" (118vac) to the metal stand I read a steady 171vac!!!
From house ground to PVC drain pipe is 0vac
From house ground to kitchen sink drain is 0vac

The fact that the stray and mysterious 52vac is in addition to the house "hot" informs me that it must come from another phase (only stove/dryer and h2o heater on 220vac) - HELP anyone???!!!!

Thanks in advance!
Quint
 
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Old 06-01-15, 07:07 PM
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You are using a digital voltmeter aren't you? What you are reading is not a true voltage but what is called a "phantom" voltage.

Here is pdf from Fluke describing the phenomena. http://support.fluke.com/find-sales/...105317_A_w.pdf

Google phantom voltage for more articles.
 
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Old 06-01-15, 07:27 PM
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Shut off each breaker, one at a time until the voltage disappears.
 
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Old 06-01-15, 07:58 PM
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Welcome to the forums.

The faucet is grounded but the metal frame around the sink is not.
A picture of this sink would probably be helpful. http://www.doityourself.com/forum/el...rt-images.html

Induced voltage but induced from what ? The sink isn't wired.

It would be interesting to see which breaker affects the problem.
If you have an electric dryer.... try unplugging it and see if that has an effect.
 
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Old 06-01-15, 08:14 PM
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Thanks for the responses.

That 52vac phantom voltage sure does ZING whenever touching our streaming faucet (I do contract eng. work for Fluke). Getting shocked lead me to investigate.

Good idea pulling the breakers - will pass along my findings.
 
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Old 06-01-15, 10:24 PM
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Wow, I'm really batting .000 today. Most commonly the problem IS reading a phantom voltage, obviously not this time.
 
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Old 06-02-15, 03:15 AM
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Is that particular sink the closest fixture to where the panel box grounds at the water pipe? Is the ground tight?
 
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Old 06-02-15, 05:35 AM
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Can that phantom voltagel light up a 25 watt or smaller incandescent lamp? Make the same measurement but with the lamp across the two test points (e.g. sink and ground rod) at the same time the voltmeter test prods are across the same test points.
 
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Old 06-02-15, 06:27 AM
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First step is to turn off the main breaker and see if the problem persists. This will tell you if it's your problem or the power company's problem. If it is your problem, turn off breakers one at a time until you identify the source of the problem. A good place to start would be the electric water heater element.
 
 

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