Induced Voltage?

Merry Christmas
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Murgs

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Fire Safety
I'm a homeowner, so I appreciate your time and advice on the matter. I had an electrician look at it, but he seemed dumbfounded.

I hung a 60" x 30" metal framed mirror. I was aware of wiring running along one of the studs that I planned to use for the hanger, so I was careful. I ran the screw without an issue. After it was hung I tested the frame with a noncontact voltage tester and got positive readings along the entire frame. I was obviously concerned that I ran through a circuit. I cut a hole in the drywall next to the screw. No wiring runs through the stud, and I do not believe the screw has contacted a circuit. Running vertically along the stud are three circuits- a 10/3 circuit and two smaller circuits that appear to be 12/2 or 14/2. The mirror is hung vertically so the metal frame runs parallel to these circuits. The screw in question reads positive with the voltage tester. FYI-The second screw used to hang the mirror is likely not near any wiring, and it does not read positive with the mirror removed. I would very much appreciate help with the following questions:
  1. Do I have a problem?
  2. Is there an induced voltage on the frame of the mirror?
  3. If so, does that indicate some other problem? (I read somewhere that induced voltage could indicate an issue with the grounding of circuits that cause an induced voltage)
Thanks again for your time.
 
Murgs said:
I'm a homeowner, so I appreciate your time and advice on the matter. I had an electrician look at it, but he seemed dumbfounded.

I hung a 60" x 30" metal framed mirror. I was aware of wiring running along one of the studs that I planned to use for the hanger, so I was careful. I ran the screw without an issue. After it was hung I tested the frame with a noncontact voltage tester and got positive readings along the entire frame. I was obviously concerned that I ran through a circuit. I cut a hole in the drywall next to the screw. No wiring runs through the stud, and I do not believe the screw has contacted a circuit. Running vertically along the stud are three circuits- a 10/3 circuit and two smaller circuits that appear to be 12/2 or 14/2. The mirror is hung vertically so the metal frame runs parallel to these circuits. The screw in question reads positive with the voltage tester. FYI-The second screw used to hang the mirror is likely not near any wiring, and it does not read positive with the mirror removed. I would very much appreciate help with the following questions:
  1. Do I have a problem?
  2. Is there an induced voltage on the frame of the mirror?
  3. If so, does that indicate some other problem? (I read somewhere that induced voltage could indicate an issue with the grounding of circuits that cause an induced voltage)
Thanks again for your time.
Click to expand...
1. No
It’s induced voltage. Have your electrician use a low impedance voltmeter. If he does not know what that is, find another electrician.
 
Thanks so much for your replies. I noticed after I posted that the forum is intended only for industry folks, and I appreciate your kindness in allowing it. I'm in a related industry, but this was of course, a personal issue.

I will let the electrician know. I use a big company, and I got a junior guy on an emergency callout. The funny thing is- I called an estimator at the same company the next day, and he seems to me to be sharp as a tack. I explained the situation to him and my theory that it was induced voltage, and he said that it would be extremely uncommon to see voltage on the frame of a mirror. He went on to suggest that I call the office and request a senior electrician. But they're at least two weeks out unless I want to spring for another 2 hour minimum at 200 bucks an hour. I think that I'll find a new electrician.

Again, I appreciate your time and expertise, and my kids just got an extra $400 in the Christmas fund thanks to the community. Have a great holiday.
 
Those non contact testers pick up on lower potential energy level "capacitive coupling" Your mirror frame might well be placed where it has no direct electrical connection to anything but is also in a location where it can be capacitively charged by nearby electrical wiring. This charge will be a low level charge and has very weak power level it can deliver.

If you have wall luminaire(s) in close proximity to the mirror it could be coupled to those, and if they do not have proper equipment grounding the chances of this happening does increase.
 
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