Voltage on chasis


Old 07-26-05, 11:04 AM
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Voltage on chasis

I was doing some work on a computer in my garage and noticed that when i touched the chasis I got a little tingle.

So I got out my multimeter and sure enough there was 38 to 40 votls AC between the netral and the chasis. Then I checked my work computer 10 feet away that was running and also got a tingle from the serial port on the back. What is cauing this? Is this just a result of ungrounded wiring. While my house has many 3 prong outlets none of them are correctly grounded. Isn't the neutral supossed to be at ground potential. I tried unplugging major appliances and nothing changed. I used to do electronic work but it has been a long time.

Any thoughts would be appreciated. (Other than call an electrician)

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Old 07-26-05, 11:27 AM
Join Date: Sep 2003
Location: Central New York State
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The neutral of a circuit is a current carrying conductor. You will get a shock and could get killed from a neutral just like from a hot wire.

You should not have three prong receptacles in your house unless they are either properly grounded or protected by a GFCI. You should not be using a computer on a circuit unless it is properly grounded.

I suggest that you replace the ungrounded three prong receptacles.
Old 07-26-05, 11:43 AM
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Originally Posted by bseyd
Is this just a result of ungrounded wiring. While my house has many 3 prong outlets none of them are correctly grounded.
Computer power supplies need a grounded outlet to work properly. Having three prong outlets without a ground is a code violation if not protected with GFCI and labeled with a "No Equipment Ground" sticker. Whether or not you created this problem, you should fix it by replacing the 3 prongers with 2 prongers, adding GFCI protection to the ungrounded circuits, or adding ground wires. The last option is very time consuming and must be done properly.

The computers should really have grounds.
Old 07-26-05, 02:54 PM
Join Date: Sep 2000
Location: United States
Posts: 18,497
Because the chassis of the computer is isolated from ground (and really from everything else), you are probably getting a static charge, and measuring static voltage. Remember Van de Graaff generators that are used to entertain kids. You can get a tingle or zap from them, and you can read thousands of volts from them, but they won't kill you (usually).

But please ground your computer, not to a water pipe or a grounding rod, but to the electrical panel.

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