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From:
Richard Glazier <[log in to unmask]>
Reply To:
Personal Computer Hardware discussion List <[log in to unmask]>
Date:
Wed, 17 Jun 2009 17:34:56 -0400
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I've been "burnt" on this list before talking about electricity,
(pun INTENDED), so I'll be brief and somewhat vague,
but forceful.
Replies mixed in.   Rick Glazier

From: "Dean Kukral"
> In an ideal world, the neutral wire is the shortest, most conductive path to ground.

Partly true, but should not be used as such. Substitute path to cener tap
of the power companies transformer instead. (See link below.)
A PROPER GROUND WIRE, PROPERLY BONDED IN CERTAIN CODE
SPECIFIED PLACES should be used (correctly) for the most conductive path
to ground.

> (On my house, the metal screws on the outlet boxes are not grounded.
> So, connecting to them does nothing.)

This is WRONG, and very, very bad -- IF actual ground wires exist at
those locations.
IMHO, you need to find out if this statement is correct,
and if so correct the DEFECTIVE condition that allows it to be so.

> Unfortunately, the real world and the ideal world are not always the same.

No, but they SHOULD BE FORCED to be similar, especially when safety is involved.

> Now, suppose I have my computer connected, that is, "grounded," to my wall outlet box.
> I am actually connected to the "neutral"
> wire, which is every bit as "hot" as the two hot wires.

Not if it is properly bonded as it should be.
Study the theory more, and repair this condition.
This is not the proper place to say how exactly.

> So, suppose that I am working on my so-called "grounded" computer and I accidentally touch some metal which is connected to 
> ground.
> In the ideal world, not much would happen, because the ground to earth path through the neutral wire is likely of much lower
> resistance than the ground to earth path through me. I suppose that I could get a mild shock, if it were not.

For some reason, you seem to be using the terms "neutral" and "ground" interchangeably.
IF you are because of  the house condition, that should be fixed.
They are not and should not be thought of as the same thing.

> So using as an example my own house, you should be able to see that there is a very small, but finite chance that by using the
> ground on the wall outlet to ground your case, you run the risk of severe injury or electrocution.  You should not trust the 
> wiring
> of your house to be properly grounded!

This is correct and if everything is as you say, your house has problems.

> Furthermore, in is not necessary to ground the case at all!  Why are  you grounding the case?  The whole purpose of all this is to
> ground YOU, not the case!!  Grounding the case does nothing to ground you.  All it does is **help you to come to the potential of
> the wall socket,** for which there is a small chance of danger.  For years, the best way to ground yourself prior to working on 
> the
> insides of your computer has been to use a wrist strap clipped to the case of your computer.  It is still the best way!

The whole purpose is to bring things to a common electrical "state".
Bringing "almost" everything to an actual ground potential is the goal.
(Not the "hot wire" of course, that goes to "neutral" through a load.)
In a perfect world, neutral and ground should be separate and at the same potential.

If that can't be done, for the purposes of a computer discussion,
I agree it might be better to let everything be "floating", but that
does nothing to fix the problems with the house.
That also explains why there are two schools of thought on this.

This is where it gets sticky... The house is not safe, so working on the computer
using standard procedures that "assume" everything is "OK"  is a bad idea.
Note that using "work-arounds" is NOT safe for you or the computer.
Sounds like I'm tap-dancing and running in circles.
This needs to be seen and fixed in person by qualified personnel.
It is almost impossible to explain without an on-site survey.

I found a very good reference here:
<http://en.wikipedia.org/wiki/Electrical_wiring_(United_States)>
I glanced through it and it explains everything I tried to say, but better.

If I were you, I'd contact Rode off list. (NOT me.)

CC: kukral@xxxxx
Rick Glazier

>
> Dean Kukral
>
> PS: Are there any master electricians out there that can confirm or deny what I am saying about house wiring?  While I have a 
> MSEE,
> it is in hardware, and it is not the same as knowing anything about wiring a house!
>
>                         PCBUILD's List Owners:
>                      Bob Wright<[log in to unmask]>
>                        Mark Rode<[log in to unmask]> 

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