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Mystery voltage

Bwana

Well-known member
Joined
Sep 11, 2012
Messages
86
Location
Santa Fe, NM
We just upgraded our cable system to HD so each TV now needs its own decoder box. The CRT TV in the master bathroom used to be in a recess in the upper wall using a GFI receptacle and a coaxial plug. When we had the bathroom remodeled, we put in a flat screen at the same location and covered the recess with dry wall. The remodeler simply left the TV power plug plugged in to the existing receptacle and ran both the power cord and the coaxial cable thru a hole in the dry wall. Pretty bush I know but we missed it as it was behind the TV.

So now with the upgrade, I was planning on moving the receptacle out to the wall so I can plug in both the TV and the decoder box right behind the TV. As I don’t want to tear out a whole section of textured and painted dry wall and take down the TV, I was planning on powering up the new receptacle with an extension cord plugged into the original receptacle and then cut and stripped then wired to the new receptacle on the wall. OK, just get it over with and shoot me now, it’s not much better than the original BS setup.

The problem I’m having is I’m getting 45VAC in the new receptacle and can’t figure out why. I’ve checked the POS extension cord/new receptacle on a known receptacle and I get 120 VAC as it should be. Power and neutral are in the correct positions. So my “extension” is not the problem. When I plug it into the old TV receptacle in the recess, I get 45 VAC on my VOM. We have gone around the house and tripped every GFCI we know of but there’s no change on the 45 VAC in the old receptacle.

The TV has worked for more than a year before I started messing with the setup. I’m hesitant to plug in a $400 TV just to see if it would work on 45VAC so I can’t tell if the 45 VAC has been there for a year or if it just happened. Do flat screens care what the minimum input voltage is? I did touch the receptacle terminals and got a minor buzz from the new receptacle so possibly I tripped the GFCI? But shouldn’t that give zero volts, not 45? We checked some receptacles in another bathroom with the VOM and that was indeed the case, zero volts on a tripped GFCI.

So how can 45 VAC show up on a household circuit? And how do I find a possibly hidden GFCI? Is a GFCI the problem?

And please save the safety lectures for both myself and other readers. I’m well aware of the rules I’ve broken but also well aware of the risks. :shocking:
 
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larry_g

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Joined
Apr 28, 2007
Messages
16,874
Location
oregon
I would suggest that you plug in an incandescent light into the receptacle and then measure what the voltage is and see if the lamp lights. If it is ghost voltage then it should go away with the load.

lg
no neat sig line
 
OP
B

Bwana

Well-known member
Joined
Sep 11, 2012
Messages
86
Location
Santa Fe, NM
If you're using a digital meter to measure it, you may be seeing a ghost voltage: http://support.fluke.com/find-sales/Download/Asset/2105317_A_w.pdf

I'm familiar with ghost voltage. We had it in a gas turbine/compressor package we had offshore. All the cabling from the front of the package was tied together and routed to the rear of the package. I remembe we had 125 volts on a supposed dead buss (can't remember if it was AC or DC). Gave my tech a bit of a thrill which is why we tracked it down! Although ours was "induced voltage" because of the power cable bundling, is this different than "ghost voltage"?

start tracing back from the outlet. Maybe the outlet is bad and not giving out the full 120 volts. Work you way along until you find the voltage drop.

Good idea but a bit impractable. The j-box is at the far end of the house in the attic, as far as you can get from the access stairs and still be in the house. And the hole in the dry wall just barely fits my arm, it's still inside of the cover plate outline and I'm trying not to tear out any more dry wall. Although I suspect this is what I will ultimately have to do to find the GFCI.

I would suggest that you plug in an incandescent light into the receptacle and then measure what the voltage is and see if the lamp lights. If it is ghost voltage then it should go away with the load.

lg
no neat sig line

Excellent suggestion! So if it's ghost voltage the lamp probably won't light, correct? My power drill does not work at all. I'll check tomorrow. (its after wine-thirty here now.)
 

lbmcse

Active member
Joined
Apr 22, 2013
Messages
30
I'd be curious to know if your hot to neutral yields the same 45VAC as your hot to ground. Perhaps the contractor swapped neutrals inadvertently?
 

LS6 Tommy

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Dec 27, 2013
Messages
26,162
Location
Northern NJ
Did everybody miss the fact that it's illegal to power a receptacle with an extension cord? That's even more "bush" than what the contractor originally did...

Tommy
 
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larry_g

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Apr 28, 2007
Messages
16,874
Location
oregon
Did everybody miss the fact that it's illegal to power a receptacle with an extension cord? That's even more "bush" than what the contractor originally did...

Tommy

Did you miss
And please save the safety lectures for both myself and other readers. I’m well aware of the rules I’ve broken but also well aware of the risks.

from the OP?

lg
no neat sig line
 
OP
B

Bwana

Well-known member
Joined
Sep 11, 2012
Messages
86
Location
Santa Fe, NM

That's really cool! I probably would have used that if I hadn't finally sorted it all out. Thanks!

The OP doesnt care about safety or code or doing things correctly....


Actually, yes I do. For instance, all the power and wiring to my shop is code as well as everything in it. I did it myself and had a code electricial buddy check it all out. I just couldn't stand tearing the bathroom wall out to redo something that should have been done the first time.

And you will all be happy to know that I ended up doing it right! There must be some sort of nanny safety nazi device in either the extension cord or the receptical that drops the voltage to unacceptable levels when you put them together.

For some strange reason, I plugged my power drill directly into the outlet in the recess and Whoa! It worked! Full voltage! This was after another trip into the attic to the farthest point in the attic you can get to and still be in the house. I dug down thru the insulation and confirmed, contrary to what's on the sticker on the receptical face plate, there is no GFCI in the circuit. It's fed directly from one of the hot leads in one of the lighting circuits. So it was the ******* pigtail that was causing the problem somehow.

I ended up covering the hole in the drywall with a tandem plate cover, using one side with a coax plug and the other side with one of those "universal" push thru panels. All's safe and legal again!

Thanks for the help!
 

CNGsaves

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Joined
Sep 26, 2012
Messages
13,233
Location
KS and OK
OP . . . why can't you cut small holes in drywall at each end, and use fishtape to pull through PROPER wire and make attempt at doing it right ??

Those two small holes in drywall can't be that hard to patch.
 
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