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I found out (in a rather uncomfortable manner) that there is a potential difference between the phase line in my home and the ceramic tile floor. My Fluke multimeter reads 30V AC, I assume the reading is inaccurate because of the low conductivity of the tile surface. However, there was enough current to give me an unpleasant shock. I was dry, but my skin was in contact with the floor.

How is this possible? Are there tiles made of ceramic-like materials that are conductive? Are conductive ceramic tiles sometimes used in home construction?

  • Sounds more like a outlet that has the hot and neutral reversed. As an owner of many fluke meters they will show a potential voltage on a piece of wire that has no connection to anything but runs parallel to another wire for a few feet. A outlet tester may be a good investment to verify the wiring is correct. – Ed Beal Aug 30 '16 at 0:36
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    You don't need to have a 'good' connection to ground in order to get a shock from touching a live wire. Capacitive coupling will do the job just fine. – brhans Aug 30 '16 at 2:34
  • Related: Electric shock, Tools, Phantom voltage – RedGrittyBrick Aug 30 '16 at 11:08
  • Can you define "phase line" ? I think @EdBeal is wrong about the "no connection" wire because you've clearly got enough amperage to feel the shock. If the hot-side is the only side that reads a voltage, well, that's to be expected. Your floor is connected to earth via high resistance. – Carl Witthoft Aug 30 '16 at 15:25
  • By phase I mean the hot line going to a power outlet (neither neutral nor ground). The high resistance is why I was surprised to have felt anything, as I'm pretty sure I only touched the line and the dry, indoor ceramic floor. – user2647513 Aug 30 '16 at 20:42
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Check the voltage with an analog voltmeter. Digital voltmeters will register a voltage from almost anything as they have a very high impedance and draw very little power. You could also use a regular incandescent bulb and see if it glows a little.This will let you know if there is any power behind the voltage. If by phase line, you mean the neutral incoming wire, it's possible it's not groundedat the panel and/or the pole transformer. Measure from the neutral to ground to see if you have a potential difference. It's possible the shock you received was static electricity and nothing to do with voltage difference between the tiles and the neutral..

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What were you touching when you first felt this shock? I have been shocked by a dry concrete block wall. Ceramic is porous and can have absorbed water even if it appears dry, grout too. I'd be more concerned with the voltage between the hot spot in your floor and ground. If your floor is on the slab ie ground, there's supposed to be a 120V potential between your floor and the hot wire. That means there could be 90V between your floor and ground. That would be dangerous. There is possibly a short between one of the hot wires and the floor. Check the potential between that spot in the floor and ground or neutral if you can't find a ground wire.

  • The grounding structure is the steel in the cement. Where you come up with 90V between the floor and ground is beyond me. There should be ~120V from the hot to the neutral or ground wire not to the floor. An outlet tester would be the first verification to make sure the hot and neutral are not reversed. – Ed Beal Aug 30 '16 at 13:53
  • The steel is in the cement, attached to the tile, all have continuity to ground with varying degrees of resistance. You have to think this all came about when the poster felt a shock from the floor. I doubt the they were holding a hot wire, if so then the mystery of the shock is solved. If you get a shock from the floor what is the point in measuring volts between the hot and the floor? There is no normal reason for a person to come into contact with the hot wire while touching the floor except a faulty ground. The world is full of H-N reversals, thankfully hot floors are pretty rare. – Francis Aug 30 '16 at 15:02
  • As I said the outlets need to be tested. But this would not make the floor hot. The outlet frame can be hot and 30v measured with most fluke means very little. It would be hard to feel 30v unless broken or wet skin. – Ed Beal Aug 30 '16 at 19:11
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    I did indeed make contact with the hot wire, this was not unexpected, the breaker wasn't turned off. Safety aside, I'm trying to understand how I felt anything by completing a circuit through dry ceramic tile, which should have resistance on the order of mega-giga ohms. This was indoors in an occupied, air conditioned house, nothing had been spilled in that room, the floor was dry. – user2647513 Aug 30 '16 at 20:45
  • @user2647513 It takes a very small amount of current flowing across the heart to kill someone. It takes a tiny amount to feel a shock. If you had a significant circuit from your arm across your heart and through your feet you could have been killed. The floor is not very conductive and that's a good thing for you. – JimmyJames Aug 16 '17 at 14:17

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