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Old 06-23-2010, 04:01 PM   #1
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Getting shocked by multiple metal items in room


Hello all,

I wanted to explain a very strange situation that is occurring in one of the rooms in my house, and see if anyone could provide a reasonable explanation.

Safety Disclaimer: I am having a qualified electrician come out, and don't plan on touching any of said electrified items any more. I am more interested in understanding the cause of these effects to improve my knowledge of electrical theory. The guys coming out probably don't have the patience to explain it to me, so would be real interested to see what the forum has to say.

Ok, so here's what's going on. I have an electrical circuit in my house. The wiring probably dates to the early '50s, and is old cloth covered wire (I believe it is copper on this circuit, although I have noticed some aluminum wire still in use elsewhere in the house). This cable does not have a ground wire. The circuit supplies a receptacle in the living room, as well as several outlets in a bedroom. In this bedroom, it delivers power to some receptacles, a ceiling fixture (currently a fan), and a closet light with pull chain. The ceiling fixture has one hot wire that goes to a light switch in the wall (wired to light kit), as well as an always on hot for the fan motor...note that these are both on the same circuit. Now, here's the problem:
  1. the fan has a pull for both the light and motor...the light pull chain is electrified. Oddly, the motor chain is not.
  2. The pull chain for the closet light is electrified sometimes (not now from what I can tell).
  3. Ready for this? There is a curtain rod by a window. Obviously, this is not an intended outlet for power, but the curtain rod is electrified. However, there are blocks of wood screwed into the ceiling, and the metal curtain rod is attached to these wooden blocks, so I'm guessing maybe the rod, touches a screw, and the screw goes into the attic and touches something else that is live?
So...thoughts? In retrospect, I see that in each case where a shock was encountered, it was when my body was sufficiently grounded...i.e. when I was adjusting the curtain while standing on a wooden chair, all was well. When I reached up to adjust it a moment later while standing on concrete floor (with rebar underneath), I was unpleasantly surprised to receive a nasty shock. Let me show my ignorance here, but I'm assuming one cause of this is that somewhere on the circuit, a neutral wire has become disconnected, thereby not providing a path for the electricity to return to the neutral buss bar and the ground rod to the earth...thus when a human becomes a path to ground, the electricity flows through them so the electricity can return to its source. Another theory is that somewhere along the hot wire, it has a place where bare metal is touching some other metal object (or multiple metal objects)...

Curious for insight on this question:
  • The fan is almost completely made of metal. It has a metal plate housing the light kit cover, and from this dangle two metal pulls, one for lights, and one for motor. Why might it be that the light pull is electrified, and the fan pull is not?
Also, if anyone has the patience to help me understand testing better...

  • If I hold a simple voltage detector (one of those pen style ones) near any of said items, it goes off immediately. I would venture to say there is a lot of voltage going through these items. For example, the detector goes off when held about 18" below the fan, and maybe 12" below the curtain rod. If I take the leads of a multi-tester (set to detect Volts), and put them on the curtain rod, I get nothing. I assume this is because there is no path to ground?
  • I tried a suggestion from this thread, where I plugged a long extension cord into a known good outlet on another circuit (still no ground wire of course), and hauled it into the electrified bedroom. I put one lead from the multi-tester into the neutral slot on the extension cord, and the other lead onto the electrified curtain rod. Here are the results:
    • Plug one lead of tester into extension cord neutral, the other lead sitting in air: averages 2.0V.
    • Plug one lead of tester into extension cord hot, the other lead sitting in air: 13V
    • Plug one lead of tester into extension cord neutral, the other lead touching fan's light cord: 2.2V
    • Plug one lead of tester into extension cord hot, the other lead touching fan's light cord: 119V
    • Plug one lead of tester into extension cord neutral, the other lead touching curtain rod: 1.1V
    • Plug one lead of tester into extension cord hot, the other lead touching curtain rod: 13V
  • Finally, one more strange observation, that may help explain this whole thing. If I plug the extension cord into a switched outlet on another circuit, and turn the switch off (assuming this means no power delivered to cord, but still provides a path back to earth through neutral buss bar), I noticed the following:
    • One lead plugged into extension cord neutral, other lead touching fan's light cord: 118V
    • One lead plugged into extension cord hot, other lead touching fan cord: 118V
    • If I try this same experiment, but while touching the curtain rod, I don't get any noticeable voltage from either configuration. So seemingly the fan has a different behavior.
Thanks for any help or insight that you can provide!

Thomas


Last edited by thms; 06-23-2010 at 04:14 PM.
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Old 06-23-2010, 04:08 PM   #2
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Getting shocked by multiple metal items in room


thms - give us your location and we can better comment about some of these issues. Good on you for trying to educate yourself

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Old 06-23-2010, 04:13 PM   #3
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Getting shocked by multiple metal items in room


Quote:
Originally Posted by Leah Frances View Post
thms - give us your location and we can better comment about some of these issues. Good on you for trying to educate yourself
Thanks, Leah...I'm in the southwest USA
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Old 06-23-2010, 04:41 PM   #4
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Getting shocked by multiple metal items in room


Is this a plaster-lath house as opposed to a drywall house?

Sometimes a metal screen is used as the lath instead of thin wood strips. Such a lath could conceivably become electrified where a wire passing through had the insulation worn through. Then if curtain rods, etc. are screwed into the wall, they can be electrified depending if the mounting screws or nails hit the screen.

Because many square feet of wall and ceiling surface may be electrified, and electrical fields are formed about objects electrified with AC, pen type electrical testers may behave unpredictably in the room.
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Old 06-23-2010, 05:28 PM   #5
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Getting shocked by multiple metal items in room


Have you used a tester to find out how much voltage is present in the objects? Is it full 120?
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Old 06-23-2010, 05:38 PM   #6
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Getting shocked by multiple metal items in room


Just like to request that when your electrician finds the cause, that you relay it to all of us if you can. Thanks
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Old 06-23-2010, 06:55 PM   #7
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Getting shocked by multiple metal items in room


@AllanJ: Good point, I never even thought about that, that could be a potential cause. As for the house construction, as far as I can tell, the exterior walls are block, and the interior walls are plaster...since I've lived here, I've only had to cut a couple of holes in the interior walls (for installing low voltage boxes and wiring phone lines)...during those cuts, I never saw any actual wire mesh lath material, but that doesn't mean it's not there. I believe the exterior walls are just block though, and the curtain rod in question is right next to an exterior wall, if that helps. Keep in mind though, the curtain rod is mounted onto three wooden blocks, and the wooden blocks are screwed into the ceiling...might the ceiling conceivably be constructed with a lath screen?

@secutanudu: Yes, all of the measurements I took are listed in the first post.

@Troglodyte: definitely will post the results when this gets resolved
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Old 06-23-2010, 07:08 PM   #8
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Getting shocked by multiple metal items in room


On plaster walls, there is often metal mesh in the corners even if there isn't any on the main wall, if a wire has energized mesh there and the curtain rod is close that could be a possible culprit.

If you are bored and comfortable with electricity, you could try and determine the 'order' of the receptacles and lights by unattaching one and seeing what still has power, while simultaneously seeing if the curtain rod is still energized and if the ceiling fan is still energized. This could allow you to narrow down where the problem is occuring and might help cut down on how much time the electrician will spend doing the same thing (if he will do the same thing that is).

Can you get at your ceiling fan from the attic?
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Old 06-23-2010, 07:27 PM   #9
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Getting shocked by multiple metal items in room


Measure your danger- put 5 ea. 15,000 ohm 2 watt resistors from Radio Shack or a similar place in parallel to make a 3,000 ohm 10 watt composite resistor.
Put this between the two points that shock you and measure its voltage. For most people, 3v or less is barely detectible, 30v is painful and 60v is dangerous.

This technique may trip upstream GFCIs.
If ground is one of your contact points, you read 15v or more and you have an upstream GFCI, it should trip.

Concrete is pretty conductive.
http://en.wikipedia.org/wiki/Ufer_Ground

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Old 06-23-2010, 08:20 PM   #10
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Getting shocked by multiple metal items in room


@Troglodyte: That's something I can do...I have a good guess on the order of outlets. After work, I could run through that: with breaker off, disconnect an outlet, cap and tape ends, turn power back on, and see what still has power, and if the curtain rod and fan are still electrified. I'm assuming this exercise helps narrow down where the problem starts, so I can save the electrician some time? In other words, identify in which part of the run the problem starts. As for the ceiling fan access, I'll check that too. Unfortunately, it's pretty hard to get to anything up there, as the builder put a type of second ceiling about a foot over the lower ceiling, and most of the wiring and outlets are in between, which makes access a real pain.
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Old 06-23-2010, 08:56 PM   #11
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Getting shocked by multiple metal items in room


You could also try to isolate which circuit was causing the problem before you started taking the circuit apart.
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Old 06-24-2010, 08:37 AM   #12
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Getting shocked by multiple metal items in room


I have seen metal lath screen in ceilings too.

If the house had been remodeled, it is possible that metal lath covers only part of a wall or ceiling.
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Old 06-24-2010, 09:47 AM   #13
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Getting shocked by multiple metal items in room


What if there is some conduit or greenfield used in this house that is in contact with something like the mesh. If there is a hot box from poor insulation or a bad connection, then the conduit could be what is spreading the juice around. I think turning off one circuit at a time is the best ideal.

Quote:
So...thoughts? In retrospect, I see that in each case where a shock was encountered, it was when my body was sufficiently grounded...i.e. when I was adjusting the curtain while standing on a wooden chair, all was well. When I reached up to adjust it a moment later while standing on concrete floor (with rebar underneath), I was unpleasantly surprised to receive a nasty shock.
You may have more things hot in this house than what is realized so far but you just don't know it because there could be insulated floor covering preventing a ground path.

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Old 06-24-2010, 02:18 PM   #14
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Getting shocked by multiple metal items in room


@AllanJ: I'm starting to think lath in ceiling is probable..last night, with power off, I removed curtain rod. Turned power back on, and found (with multi-tester) that a metal anchor (from curtain rod mounting job) embedded in ceiling was hot (118V). Turned power off, removed anchor and looked up with flashlight...there were no wires visible that could be touching that anchor...so something conductive that was electrified must have been in contact with the anchor...wire mesh in plaster ceiling is a likely case. In general I've noticed that if I walk around that room with a voltage detector, it goes off continually if it's within 18" of any part of the ceiling. When I exit that room, the detection stops...in the rest of the house, you do not get this behavior.

@a7ecorsair: from what I see up in the attic, no armored cable etc. is in use. Just a bunch of old cloth wrapped 12/2 with no ground.

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Old 06-24-2010, 02:23 PM   #15
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Getting shocked by multiple metal items in room


So electrician is hopefully going to make it by today. In the meantime, I inspected all of the receptacle and fixture hookups to see if I could find an improperly-connected neutral. One really disturbing thing I found is that on one receptacle, there is one set of line wires (hot/neutral, no ground) and two sets of load wires (2 x hot, 2 x neutral, no ground) attached to the receptacle screws. So it looks like someone decided to tap the receptacle for a second run instead of doing a junction with wirenuts in the box. This seems like a patently bad idea, although I'm not sure it is what is causing the issue. When electrician arrives, I'll post his assessment back to this thread.

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