Getting small shock from household electronics cases (in Asia). Why?

Discussion in 'General Electronics Chat' started by scootley, Oct 27, 2009.

  1. scootley

    Thread Starter New Member

    Oct 27, 2009
    19
    0
    Hi,

    In my apartment, if I touch the bare metal case of certain electronics with a bare finger (in particular the back of a knuckle) while standing on the floor with bare feet, I get a tiny shock.

    This happens with the metal case of a DVD player, the bare metal of a TV antenna, the bare metal of a laptop case, and the bare metal of a capacitive touch volume control on a set of speakers.

    I live in Asia, and we have 230V power with type F outlets.
    Some of the electronics that give these tiny shocks are connected to the ground (earth) pins of the outlets, while some are not.

    So what is causing this? Is it that the AC neutral wire in my apartment is at a different voltage than the earth? Or is it that the ground/earth wire in my apartment is not actually connected to the earth? Or could it have something to do with incorrect polarization (plugging the live AC wire into neutral), since type F outlets are not polarized?

    As a related question, how does grounding work with external AC-to-DC power supplies? So for example if my laptop's power supply AC plug has a connected ground pin, but the output DC connector is just 2 pins (plus and minus), is one of these 2 DC pins connected to the metal case of the laptop? Which one? And is one of these 2 DC pins somehow connected to ground? How?

    See a Type F connector: http://electricaloutlet.org/type-f

    Thanks
     
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    1,758
    98
    Sounds like a shoddy product.
     
  3. scootley

    Thread Starter New Member

    Oct 27, 2009
    19
    0
    Can you elaborate? This issue occurs with a variety of products, and my sense is that it is in no way product-related but instead a problem with wiring in my apartment.
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    Sounds like you have an open ground somewhere..... if this is happening to a variety of appliances, I would suggest having a qualified electrician check your mains power and make sure it is properly connected, I would watch out when touching 2 appliances at once, you would complete the circuit and possibly get electrocuted!! I would have this checked right away.....
     
  5. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    I agree , it sounds like an open or floating ground (earth) connection.
     
  6. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    I had the same problem at home. I was a broken sewage pipe that caused the problems. This resulted in bad building ground point
     
  7. scootley

    Thread Starter New Member

    Oct 27, 2009
    19
    0
    Just to be clear, is an "open or floating ground" when the ground (earth) wiring in my apartment is not actually connected to the earth?

    Can someone explain why that causes the tiny shock when my body completes a circuit between the floor and electronics casing? What causes the voltage potential?

    Why/how would that cause electrocution? Doesn't electrocution require the live (hot) AC wire to be involved? Touching an appliance would only constitute touching the live AC wire if the polarity of that appliance's plug was reversed, since appliance cases are never connected to live but sometimes to neutral, right?

    My problem seems to be with ground and not the live/neutral polarity.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Do you have a digital multimeter? If not, you can usually find them for just a few dollars.

    Set the meter to read the highest AC voltage it's capable of. Then hold one probe tip between two fingers tightly, and touch the other probe to the appliance(s) that you are getting shocks from.

    From the "Type F" page you linked to above, it does look like it's easy to reverse the plug into the outlet.

    The neutral line must be connected to earth ground to keep it from "floating" to arbitrarily high voltages. This can easily happen if there is a fault in the high voltage step-down transformer that supplies your apartment building. The earth ground is there to protect against such faults; it will cause the fuse by the transformer to melt instead of killing people.
     
  9. maxpower097

    Well-Known Member

    Feb 20, 2009
    795
    388
    Could it be static? Only reason I say this is I live in FL where its hot and muggy all the time. I recently moved to memphis TN in the winter where it was dry and cold. I was litterally shocking myself on everything I touched. I was amazed how different static electricity worked in dry cold rather then wet hot weather.
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    I too believe the OP is simply experiencing static discharge.
     
  11. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    the op is from Asia, not much static build up in humid/hot conditions....

    if it was static, they would experience more of it even when touching other things besides appliances..... (Such as door knobs, stainless sink, etc.)
     
  12. AdrianN

    Active Member

    Apr 27, 2009
    97
    1
    Years ago, during a trip to a customer in Asia, I found out that the building had the earth ground connected to the neutral line. They had the same problem. You would get a small shock if you would touch the enclosures of two instruments. This mostly happens if the two instruments are connected to two different outlets, each one on a different phase. Things are aggravated if there is a large power consumer in the neighborhood like the building elevator.

    The customer solved this by isolating his lab with a transformer and created his own good Earth ground on a pipe line. This may be too drastic for your apartment. You may have type F outlets, but if the ground and neutral are wired together the ground is useless.

    I would suggest you connect adjacent devices in the same outlet, with extension cords. A more elaborate solution is to rewire each room outlets to one single phase per room. I also recommend for you to use a qualified electrician for this.
     
    Last edited: Oct 27, 2009
  13. maxpower097

    Well-Known Member

    Feb 20, 2009
    795
    388
    The only reason I said static is if he's feeling it on the back of his knuckle , thats a very sensitive part of your body like your lips. So I wondered if it was small enough to be a static shock. Lets run some test's. Hey poster, try to kiss your appliances and see if the shock feels stronger or weaker. :) :) :)


    J/k don't kiss your electronics. :)
     
  14. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    I live in the US and don't have any experience with your Asian wiring's characteristics, but if this was happening to me in a US apartment (actually, anywhere), I would label it as a serious condition (potentially life-threatening) and demand that it be understood and fixed. Put such a demand in writing to your apartment manager.

    In the US, a properly-wired wall power outlet and a properly designed and working appliance should never give a (sensible) shock to a user. The fact that you can feel it means it's on the order of one or a few mA, much too large of a leakage-type current.

    But the fact that you say it happens with multiple appliances tends to rule out the hypothesis that you're dealing with an AC leakage problem (which can be found by an AC leakage test on the appliance).

    Unless you know what you're doing, I recommend you get an experienced electrician in to troubleshoot the problem. You do have to rule out static electricity, but if you're sitting down and you touch a device, get a small shock, and repeat a few times, getting a small shock each time, that's not a static electricity problem.
     
  15. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    I agree. A tiny shock is different than a continuous current. Feels alot different for sure.
     
  16. scootley

    Thread Starter New Member

    Oct 27, 2009
    19
    0
    It is absolutely not static electricity. The shock will happen over and over from the same appliance for as long as I touch my finger to it, with me not moving around. It doesn't feel like static, and the climate here is such that there is never any static.
     
  17. scootley

    Thread Starter New Member

    Oct 27, 2009
    19
    0
    I have not tried touching the enclosures of two such appliances simultaneously, although BMorse asserted in post #4 that this would be dangerous, which I said I did not understand (given my symptoms) in post #7. My problem happens when touching the enclosure and the floor (with bare feet) at the same time.

    But you have also suggested that connecting ground to neutral is bad, while SgtWookie suggests that it is good...

    So what is the story? Should neutral be connected to ground at some central building location, or not? Or maybe this practice varies by country (and AC power system)

    Wikipedia's "ground and neutral" and "earthing system" articles seem to indicate that this practice varies by country and type of user.

    I am not planning on doing these repairs myself, but I do want to understand them, because the electrician may not, since this is a developing country. And the electrician will not speak English, so I need to know enough relevant context on the issue to pre-translate electrical jargon into his language.
     
    Last edited: Oct 28, 2009
  18. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Not if he is getting a continous tingle, he's not. My bet is faulty wiring, it is pretty easy to check. I'm thinking it could be several things, hot and neutral swapped at a outlet, or and open neutral and ground being in the circuit path. Neither of these is good, they can be dangerous.

    I notice the socket has a mechanical keying mechanism.

    I posted this before I noticed the second page.
     
  19. scootley

    Thread Starter New Member

    Oct 27, 2009
    19
    0
    Can you elaborate on what that (open neutral and ground in circuit path) means and why it can be dangerous?

    What do you mean by that?
     
  20. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    Ground is simple a convenient reference of potential. When you stand on the floor in bare feet, you're probably connected electrically to ground, possibly through some significant resistances. The fact that you are getting a shock when touching appliances means those appliances have significant voltages on them with respect to ground. In anyone's book, that's a potentially hazardous situation.

    SgtWookie's advice of getting an inexpensive multimeter is good advice, as they can be had cheaply and can measure what's going on. Set it to AC volts and measure from ground to the appliance -- if you see more than a few volts, it's probably something you need to worry about. Then repeat the measurements on the DC voltage setting of the meter.

    The cause of this problem will need to be determined by the electrician. But nobody can argue with you if you show them these voltage measurements.

    Insist on resolution -- from what you've described, you're living dangerously.
     
Loading...