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(First time quiestion here, so correct me if something's wrong)

I recently installed a lamp on the ceiling (a metallic chandelier). Two wires connected to the ceiling (one phase and one "zero"). The grounding is connected to the top metallic part of the chandelier (the cover for the wiring). So everything is pretty much ok - the thing works as expected, all 5 lamps work and give light.

The problem: when I touch that top metallic part (the wiring cover) of the chandelier with a tester it starts flickering (a have this "pencil"-looking model of a tester). So basically some voltage there on that thing, but it is not stable - the led in the tester turns on and off at random. It is also not some temporary thing - I tried holding the tester there for longer times and it does not stop.

So the question is - should it be this way? Did I do something wrong? I mean there is not much to connect there - two wires in the ceiling (no grounding) and two wires in the chandelier. Help, please.

UPDATE

Ok, I just returned from the apartment. And I am getting a bit suspicious - the tester I got lights up even when close to pretty much any wire (the wires I tried were all isolated). The LED inside it does not go full-power though - it is quite dim when testing those wires. So, basically, it is getting some phantoms there. So again - I am starting to think that the tester I have is not going to help to find out anything. And I still do not have a volt meter so it will be a trip to the hardware store for me.

Just in case - I get no readings whatsoever with lights off. And I double-checked the neutral - it does not touch anything. In any case - I think I need a proper tester before proceeding.

UPDATE 2 Problem was solved. I was a bit (or a lot) stupid and got the wrong tester. I tried it out with a simple wire and got a reading (as indicated in the previous update). And then I got a normal tester that did not get any readings on any parts of the chandelier. I also tried it out with the phase wire coming out of the ceiling and it did light up (that way I ensured that the tester works). So again - thanks for your answers, guys. They really helped a lot.

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Is it a non-contact tester (no metal exposed on the tester), or does it look more like a screwdriver (has bare metal as a probe)? –  Tester101 Nov 30 '11 at 13:29
    
It is like a screwdriver. So yes, you test by touching the target with bare metal. –  Jefim Nov 30 '11 at 13:54
1  
Non-contact testers do not read voltage, they detect fields associated with voltage (e.g. magnetic fields or electrostatic fields). You are likely actually picking up the wires inside the chandelier. The metal of the chandelier is being affected in some way by these fields, causing it to seem as if voltage is flowing through the chandelier itself. –  Tester101 Nov 30 '11 at 14:02
    
So once again - I do have a contact tester. I have to actually touch the metal part of the chandelier with the tester's metal part. But anyway - I got your explanation. Thanks :) –  Jefim Nov 30 '11 at 14:07
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Contact type testers use your body to complete a circuit (which is safe because the neon light inside takes very low current to light). The magnetic field created by flowing electricity can induce a current on metal within it's field (Ghost voltage), which is likely what you are picking up. –  Tester101 Nov 30 '11 at 14:12

1 Answer 1

up vote 4 down vote accepted

The type of proximity tester you are using is fine for quick checks on conductors and surfaces, but not always reliable. Since they will detect voltage at a short distance, it often gives false positives due to the fact that a hot conductor is close to some other part, such as your canopy. Often an AC voltage will induce a phantom voltage on adjacent metal conductors that your tester will detect.

The only certain way to tell, if in fact you have voltage on your canopy, is to use a Volt meter. Since voltage on a grounded part such as your canopy indicates a short to ground, it should trip your breaker. Regardless, use a meter and test the canopy to the actual ground conductor for any voltage. Also test hot to neutral and neutral to ground.

Another test you can try with your proximity tester is to drop the canopy and move it away from the hot wire. I bet the positive reading will disappear. Try this with the light on and off. If you still get a positive reading with the light off, you may in fact have a short to the casing of the fixture. If the positive is only when the light is on, then check to assure the neutral is not attached directly to the fixture case, as this will cause a positive reading.

Caution is always advised with working with electricity. If you continue to get positive readings or really don't understand the theory of what I have described, then get some help from an electrician to be safe. Good Luck.

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I will try your suggestions and come back if something is not clear. But for now I guess that your answer is actually quite detailed. Thanks a lot! –  Jefim Nov 30 '11 at 14:07

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