Why a small shock through a switch that was off?

Discussion in 'Electrical Forum discussion & Blog' started by leejosepho, Dec 21, 2008.

  1. leejosepho

    leejosepho DIY scratch-pad engineer

    I just added a new circuit in my basement, and I am sure I did everything correctly. I ran Romex to a junction box, then wired down to a switchbox box with two switches. One of the switches is lighted when off, and I had the power on while attaching its single light a few feet away ... and I got a very slight shock between the bare ground wire and the black while stripping the end of the black wire. With the box grounded, the switch was lit up while the run to the bathroom light was still completely open, and I had assumed no power would be coming through the switch while it was off. So, what caused that bit of current that gave me a slight tingle? What I felt was so light that I first thought it was just from my arthritis or whatever while squeezing the wire strippers.
  2. jar546

    jar546 In the Trades

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    Unless the circuit is shut off, all switches have power to them whether they are on or off. The power is always there waiting to be sent to the fixture.
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Current flowing through the pilot light on the switch
  4. leejosepho

    leejosepho DIY scratch-pad engineer

    I suspected that, but I would think "off" would actually mean "off"!

    So then, there is always some current flowing through the light bulb on down the line even when the switch is off and even though the pilot circuit is already complete through the grounded switchbox?
  5. Cookie

    Cookie .

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    Never assume my friend.
  6. Cass

    Cass Plumber

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    Were you using uninsulated wire strippers?
  7. jimbo

    jimbo Plumber

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    The pilot circuit is NOT completed through the ground connection. It is never allowed to run any current to ground. The small current used for the pilot flows through the circuit load (light bulb, or your body!).

    This is why switched like that will often cause flakey operation of fluorescent bulbs ( flicker, etc).
  8. Thatguy

    Thatguy Homeowner

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    Yes. The 1 mA that passes through a neon lamp is just perceptible.
    I don't think most phantom voltages can deliver enough current to be sensed, unless you got the shock at the end of at least 200' of Romex.
  9. leejosepho

    leejosepho DIY scratch-pad engineer

    No, but I was touching some of their exposed area.

    I understand, but it did first light up even before the fixture and bulb had been attached ... yet now the pilot goes out when the bulb is removed from the fixture at the end of the line. Go figure, eh?! Overall, it just surprises me that "off" does not always really mean "off"!

    The shock (barely a tickle) was at the end of a 35' piece, and now that I see the switch's pilot goes out when there is no bulb at the end of the circuit, everything seems fine.
    Last edited: Dec 22, 2008
  10. jimbo

    jimbo Plumber

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    I disagree that this would be referred to as phantom voltage. It is real voltage. There happens to be a high resistance in series, which limits the current which can flow through your body.

    This probably also reinforces the idea that a switch should not be relied on as the means to remove power from a circuit prior to work.
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