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I have a weird problem regarding grounding:

I have a computer, printer and a LCD screen connected to the electric outlet through a power strip. My computer is zapping me when I touch the body so I tried to touch with a tester the screws on the computer body and saw that the light was on. Then I touched the ground hole in the electric divider and saw that it was on as well.

I thought that it was problem with one of the peripherals so I removed each one of them but as long as one of them was connected the light was on in the ground hole. If I remove all of the appliances then the light in the tester is turned off. (Also, when I touch the ground hole directly in the outlet, it's off.).

Then i thought the outlet was the problem so I connected them to another outlet but still, same thing.

So i thought the power strip was the problem so I changed to three different ones but still the same thing.

The tester light is full on, not weak, and the computer is zapping me good (not very intense but every time I touch it and it's not very pleasant). What do you think is the problem ?

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Your power supply must be fault inside the computer. For some unknown reason... which must be very rare but also very dangerous the ground(earth) is looped to voltage somewhere. It can only be the power supply inside the computer then .. nothing else.You lucky your computer did not blow up also that you still alive. It must be an el cheaopo? –  ppumkin Jul 9 '12 at 12:50
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@ppumkin I don't think it's the power supply for couple of reasons, main one is that it's not exclusive to the computer and also happens when the monitor or the printer are connected solo. also it didn't happen to me in my previous home, and also it's a good power supply from a good company. –  Michael Jul 9 '12 at 14:45
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I think this plug has been wired with a fake ground. This is where you connect the ground pin from the outlet to the neutral wire. Which is not safe. –  Brad Gilbert Jul 10 '12 at 5:02
    
I found that I had exact same problem as the poster, I have just found the cause... a 3.5mm headphone jack - when I touched my foot on the case I got a intense pain at contact point. It turned out that the 3.5mm cable was plugged into a secondary machine that I was setting up with no other cables plugged in, and when I rested my foot / leg on the towers I was getting a shock ... This is after complaining to the shop who fixed my motherboard that they have not built machine correctly. –  Daniel Jan 13 at 1:07
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2 Answers

up vote 2 down vote accepted

You most likely have poor grounding to or from the breaker box in your home.

The first thing I would do is get myself one of these nifty devices. I generally dislike the cheap tester lights as they don't tell you very much. It is called a Voltimeter and it will be able to tell you if a current is passing and how much voltage exists to your ground.

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It has many settings, for testing your typical 120v AC home outlet you can set it to test AC voltage at the ACV 200 setting. Test hot to neutral first and make sure that you have 115-130 volts on the meter display. Next test hot to ground and make sure that you get the same reading.

If you get a lower number than this or if it remains close to zero then your outlet has not been properly grounded.

Test the other outlets in the home and they register the same then it could be a problem with your breaker box not being properly grounded. It could also be if your house is older that the original outlet boxes were never grounded to the breaker, and someone had just installed three pronged outlets throughout the house without bothering to ground the outlet boxes.

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thanks ! so the voltage between hot to ground should be the full voltage swing same as from hot to neutral ? –  Michael Jul 9 '12 at 14:49
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@Michael Yes. Anything less and you are not properly grounded... which coincidentally explains why the computer case is zapping you. When you touch the computer case, YOU become the ground because the current has nowhere to go but through you. Your computer like many electronics have green ground wires that are wired directly to the body of the case. The case itself is connected to the ground prong in its plug with the purpose that any power surges will travel safely from the case to your ground plug and safely out the house to earth. This is why you are getting zapped. –  maple_shaft Jul 9 '12 at 15:03
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If your device is leaking current to ground, the device is malfunctioning. Disconnect the device from the circuit, and do not reconnect it until you have repaired the fault. There should never be current on the equipment ground conductor. –  Tester101 Jul 9 '12 at 16:10
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Your outlet may be wired backwards although there still needs to be a problem inside the computer, probably the power supply for this problem to happen. The suggestion someone is using the neutral for a ground is a good one. Also some "electricians" will use the ground wire for a neutral so they can convert a two wire cable to a three wire. I found this a lot in the Southwest in order to covert a single speed air conditioner to a two speed.

The ground must be separated from the neutral except at the service panel. Once the ground and neutral come in contact your ground becomes current carrying.

You may have a problem in your panel such as loose wiring. It's a good idea every 2-3 years to tighten up all the lugs in your service panel. A loose neutral can play havoc with your electronic equipment and actually burn up televisions, etc. I have seen panels catch fires from loose connections. The wires in the meter need to be tightened as well.

At the service panel the neutral should be grounded. It should be grounded NO WHERE ELSE!

If you have a multimeter turn off the power and check your receptacles with it. Use the ohm-meter to check the resistance between your ground and neutral. You should have no more than 7 ohms resistance between the two and closer to zero is desirable. If you have infinity then either your house is an older one or your ground is disconnected somewhere.

If your house was wired before the mid 60's it might have been wired in "flex" or flexible metal tubing. This will test as a ground but is not safe. This ground can start fires if there is a short to ground (ground fault). So called electricians will often replace older 2-prong receptacles with 3-prong receptacles. This is creates a hazardous situation. The only three prong receptacle that is safe to use on a 2-prong circuit is a GFCI receptacle. NO EXCEPTIONS!!

I understand what I have written is technical and may not make a lot of sense to a layman. If you want to make sure your house is properly wire have a COMPETENT, trained electrician translate it for you or get a licensed and reputable electrician to check your house. If he knows what he's doing it won't take long. A union trained electrician is usually a safe bet.

I have thirty years experience, have held two master electrician licenses and run my own company. I am aware of how many dangerous people are out there calling themselves electricians. I am not a union electrician but have hired them and they have always been well trained.

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While you make some good points, you did not answer the question. –  Tester101 Jan 6 at 15:06
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