Electricity shocks from PC case and usb cables

[GGOD]

hello guys i have really a big problem with my pc i get Electricity shocks if i touch my case or a usb cable that's plugged in ...altought my wall isnt grounded this doesnt happen when i plug my pc into the ups( when its not plugged to the wall).... i looked online and some suggested that it may be the PSU but i dont think so since my setup is realtively new ...

 

[Paperdoc]

If your wall outlets are not grounded then I assume they have only two slots for blades of the plug. Look at those slots carefully. On newer designs one slot is wider (well, taller if they are vertical), and the blades of the plug also are different. If that's what you have, there really should be only one way to plug the plug into the outlet.

HOWEVER, if your plug blades are the same size and the outlet slots are different, you can plug in with the plug turned either way. In that case, unplug, turn the plug over, and plug in the other way. That MIGHT eliminate the shocks.

IF, instead, the outlet slots are the same size AND the plug blades are the same size so that you can plug in either way, try doing that same thing. Unplug, turn the plug over, and plug back in. Again, that MAY solve your issue.

The source of this is that, on any North American outlet, the two slots of the outlet are one Hot and one Neutral. On SOME devices (like you computer) there MAY be a connection to a case part from the power wire in the cord that is supposed to be plugged into the Neutral slot. (There really should not be, but it does happen.) IF the connection at the wall is reversed, the intended Neutral wire into the computer may actually be the Hot wire, and that can give shocks from the case.

There's another related possible cause. With modern outlets that have a round Ground hole, the wiring supplying the outlet is connected in a particular way so that the Hot and Neutral supply lines from the breaker panel are on the correct slots of the outlet. Moreover, with a 3-prong plug you can't plug it in backwards. But with the older two-slot outlets, sometimes which slot is fed from which power wire is not done correctly. In those mistaken cases, even if you plug in correctly, the actual power being fed can be wrong. To detect this error and fix it probably requires an electrician.

If turning the plug over does not solve the problem, then there is another possibility to check. This really would require an electrician to help. There may be a flaw in the way the entire house's power system is Grounded. In North America and many other locales, the Neutral line from the power source is connected to Ground at the transformer AND at the breaker panel. If that Ground connection has failed, then even the Neutral line is no longer at Ground (zero) voltage, and lots of bad things can happen.

 

[GGOD]

If your wall outlets are not grounded then I assume they have only two slots for blades of the plug. Look at those slots carefully. On newer designs one slot is wider (well, taller if they are vertical), and the blades of the plug also are different. If that's what you have, there really should be only one way to plug the plug into the outlet.

HOWEVER, if your plug blades are the same size and the outlet slots are different, you can plug in with the plug turned either way. In that case, unplug, turn the plug over, and plug in the other way. That MIGHT eliminate the shocks.

IF, instead, the outlet slots are the same size AND the plug blades are the same size so that you can plug in either way, try doing that same thing. Unplug, turn the plug over, and plug back in. Again, that MAY solve your issue.

The source of this is that, on any North American outlet, the two slots of the outlet are one Hot and one Neutral. On SOME devices (like you computer) there MAY be a connection to a case part from the power wire in the cord that is supposed to be plugged into the Neutral slot. (There really should not be, but it does happen.) IF the connection at the wall is reversed, the intended Neutral wire into the computer may actually be the Hot wire, and that can give shocks from the case.

There's another related possible cause. With modern outlets that have a round Ground hole, the wiring supplying the outlet is connected in a particular way so that the Hot and Neutral supply lines from the breaker panel are on the correct slots of the outlet. Moreover, with a 3-prong plug you can't plug it in backwards. But with the older two-slot outlets, sometimes which slot is fed from which power wire is not done correctly. In those mistaken cases, even if you plug in correctly, the actual power being fed can be wrong. To detect this error and fix it probably requires an electrician.

If turning the plug over does not solve the problem, then there is another possibility to check. This really would require an electrician to help. There may be a flaw in the way the entire house's power system is Grounded. In North America and many other locales, the Neutral line from the power source is connected to Ground at the transformer AND at the breaker panel. If that Ground connection has failed, then even the Neutral line is no longer at Ground (zero) voltage, and lots of bad things can happen.

first of all thank you for taking time to answer ...your answer was very detailed and helpful ...but the problem is that i dont live in the US ...and here in algeria the electricity system isnt the same ...but what i can confirm is that i dont have a grounded outlet so from what you said i think it's due to that ...anyway thanks again for your answer and have a good day

 

[Paperdoc]

I do not know how electricity distribution systems work in your country. So let me add a few ideas in case they help.

First, there could be some confusion in the term "Grounded Outlet". Through most of North America (where I live) the power entering the house comes on three wires. Two of them are called "Hot" and are of opposite phases from the transformer, and the third is called "Neutral". In simple concept, electricity can flow from one Hot source through a load and return on the Neutral line. At every home the Neutral line from the transformer is connected to a true Ground (a suitable metal rod buried in the earth) both at the transformer and inside the house at the fuse box or breaker panel. Thus the electrical system Neutral line is always a true Ground reference point and is at zero volts in comparison to true Ground (the earth). It is called a "Grounded Neutral" distribution system. This means that under most circumstances you do NOT get an electrical shock from contact with a Neutral line; shocks only come from contact to a Hot line. Consumer devices like electric kettles or computers or fans always make sure their internal wiring insulates anything connected to a Hot line so you can't get a shock from the outside of the case. But sometimes their design allows contact between the outer case and the Neutral line; that is not good design, but it usually does not give you a shock. It CAN give you a shock, though, if there is a way for you to plug the power cord in backwards, and that is what I was talking about.

The confusion I mentioned, though, is this. Here in North America many decades ago we changed the way outlets and plugs are done. At one time outlets and plugs had only two identical slots (outlet) or blades (plug) as contacts. There are still lots of older homes with that system. Since then two changes have been made. One was to make one of the blades (and hence the matching slot in the outlet) wider. These are called Polarized plugs because they only plug in one way. The other was to change to a plug with a third contact, a round rod, that is to make a Ground connection. Making this change meant that all the cables in the walls from the breaker panel to the outlet have to have three wires in them: Hot, Neutral, and Ground. The Ground wire in the cables is ONLY for that purpose, and does not actually carry any electrical power. With this 3-prong arrangement there is certainly only one way to plug in something at an outlet. Many people call these outlets "Grounded Outlets", but there are still some who confuse that with the design of a "Grounded Neutral" distribution system feeding power into the house.

I don't know if your country connects one of the power lines into your home to true Ground or not. What you can try is what I suggested in my second and third paragraphs above. You may have to do this for several items one at a time to find a solution. So try this sequence.

1. Unplug all the components of your PC system - main computer, monitor, printer, and other hardware connected to it.
2. Plug in only the computer main box. Check whether it gives you a shock. Turn it on (you won't see anything on the monitor, of course) and check again whether you get a shock. If not, you can continue to the next step. If you get a shock, unplug it and turn the plug over, then plug it back in. This will reverse the connection at the outlet. See if you get no shock that way.
3. If you can get no shock on the main computer box, turn it off and go to the next device - the monitor. Make sure it is connected to your computer and plug it into the wall outlet. If you get a shock right away, unplug it and turn the plug over. If you get no shock, turn on both the computer and the monitor, then check again for a shock. If you get no shock, proceed to the next step. If you get a shock, unplug only the monitor and turn its plug over, then plug back in.
4. If you get no shock so far, turn those items off and go to the next item - your printer. Repeat the process. Check for shocks both with everything turned off, and everything turned on.

If you have any more components, keep on doing this. I hope you can find a way to get it all plugged in and working with no shocks.

 

[GGOD]

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