----- Original Message -----
From: Joan Rapier <[log in to unmask]>


> I've had several clients ask questions of me lately related to the
> necesity of grounding their computers and peripherals.  I've found
> myself at a loss when trying to explain.  I realize that's because I
> don't fully understand the electronics of using an earth ground myself
> beyond its function as a sort of "safety valve".
> I'd be greatful if any of you double eeez or otherwise knowledgeable
> 'tron folks could explain this to me.
>
> [1] Why is it important to have (earth) ground connected to one's
> computer or any appliance, equipment, etc. that has three-pronged AC
> plugs?

It keeps any STRAY current and or voltage off the case.
It keeps the case at ground potential.

> [2] Is it -(snip)- that earth ground plays an integral role in the
> engineering and function of any surge suppressor, UPS, or line
> conditioner?

Yes, it "helps to" take the surges away from the equipment to ground.

> [3] If someone is moving into a home whose outlets are not grounded (to
> do so would be very costly as the concrete foundation is not raised),
> how might they protect their sensitive electronic equipment like
> computers and peripherals?

Try to find an electrician that works around "slabs" a lot.
Fish "down" from above.
Try to run a conduit (outside?) with a grounded circuit (or two!).
Once they start adding stuff, they may need the "extra" electricity
in the room anyway...

> [4] In the case of number [3], is using GFI outlets their only option?

No,  And while GFIs will "fry" fairly quickly, I would not trust them to
really "blow up" faster than my computer. (As opposed to tripping...)
GFIs monitor the "balance" of electricity in a circuit. They protect
people because people can take MUCH more electricity that
electronic components. Look into "static", etc... You can "kill"
your computer with static you don't even notice...

> [5]Can one assume that, if an appliance, computer, etc. has a
> three-pronged outlet that its circuitry is designed to exploit the
> advantages of earth ground in the event of over-current or over-voltage?

Circuitry?  You can't even assume there is ANY circuitry. Sometimes the
ground wire is all there is...  (Especially in the case of "etc".)
They have all the "add-ons" because protection costs money, and very
little, if any, is provided with lots of equipment.  Remember that "great
price"??  Something got "cut" somewhere...

The ground wire protects in an over-current situation by making sure
the "fuse~" blows, and the current goes someplace safe.
There is no "inherent" protection from over-voltage with only a ground wire.

A ground wire is the first step, and a prerequisite for surge suppressors,
UPSs, or line conditioners.
The above is a simple description.  A lot more "could" be discussed.
Electricity is dangerous. Be careful. Protect your equipment properly.
Properly is very "subjective"...         Rick Glazier

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