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On Mon, 5 May 2008 09:28:05 -0700 (PDT), wrote:

On May 5, 10:54*am, "Dave" wrote:
I wonder why, since electrical codes in North America
and Britain require a ground connection at each outlet;
computer power cords are 3 wire?

(snip)

hot neutral ground

Meanwhile, I'm still waiting for an explanation from w_ about how
surege protection inside that computer can work? Where is that
direct connection to earth ground, without which w_ says surge
protection is impossible? Does the computer have a mythical earth
ground inside? The answer is it doesn't. It is acting under exactly
the same limitations and uses the same components, typically MOVs to
do what a plug-in surge supressor does. w-'s answer to this is to
claim that electronics, appliances, etc do not use MOVs, a claim
previously smashed, because of course they do. Plus it really has
nothing much to do with the question anyway, because the computer,
appliance, etc still HAS NO DIRECT EARTH GROUND, without which w- says
protection is impossible.

I'm curous to know how surge suppression can work without a ground
(earth) of any sort. Does the "black box" detect overvoltage and
disconnect the power like an earth leakage safety switch?

This might be fine for a TV, but surely not for a computer.

I don't recall any computer I've owned that did not have a three wire
connection to the mains. That and a MOV is OK for smallish surges, but
I believe that for a large surge, the sort that will blow a telephone
off the wall, one needs a large, short-path earth for the surge
detector to dump the extra power down.

I've got a few plug in protectors here and there to sop up a small
spike, but when a storm is within a few km, I pull the phone wire out
of the ADSL router, and the plug out of the mains. If I'm working at
the time, I might just keep a watch on the weather radar and count
lightning fashes to thunder times. It's rare that I get interrupted. I
have underground power and phone lines so that gives a little extra
protection, I believe. I've been told that Australian phone lines are
the most vulnerable, and the most urgent to protect or disconnect.
I hope to be going wireless soon which obviates this problem.

jack