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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: RE: Fortunately posted by sailor321 on June 7, 2007 at 09:32:38:
An independent earth connection for the audio system AC "ground" defeats the purpose of the AC "ground" wiring scheme. The purpose is to carry fault current back to the neutral power feed without creating a lethal voltage offset. The kind of fault this is meant to address is inside a piece of equipment with a metal case or metal protrusions that could come into contact with the AC hot and a person. There is resistance in the earth between the independent ground rod and the earth connection to which the AC power feed is connected. Ohm's Law says that fault current that has to travel through this resistance will create a voltage offset, and if the resistance is high enough, this offset might reach lethal levels. This is why the electrical code describes the size of the safety-earth conductor and the requirements for bonding separate earth electrodes.
The second problem is less likely, but more spectacular. Again, it is related to Ohm's Law. If there should be a lightning strike nearby, tremendous current (millions of amperes) will flow through the earth. The lateral component of this current will cause a voltage offset between the two earth electrodes (the original AC power connection and your independent connection) that may exceed the flashover voltage of your AC outlet device, about 6000 volts. Your equipment will see this offset (up to the flashover voltage) between the case and the neutral AC input wire, and may explode or catch fire.
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Follow Ups
- There are two problems with this, both of them possibly fatal. - Al Sekela 10:32:58 06/07/07 (1)
- I hope he pulled the 2nd ground rods out before he sold his houses.... - darkmoebius 20:32:31 06/07/07 (0)
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