W_Tom is a well known usenet kook who is also extremely dangerous. He
frequently posts lengthy diatribes on electrical subjects that have a
few grains of fact, mixed with lots of fantasy. It's easy for someone
not familiar with technical details to be fooled into thinking he
knows what he is talking about. In truth, W_tom is on a mission to
cause people to do dangerous things, such as create dangerous ground
loops in their home wiring. They may possibly be hurt or killed by
following his delibertately wrong advice. That's how he gets his
jollies. He doesn't like it at all when anyone points out the errors
or the dangers in his posts. He gets quite hysterical and nasty.
You've been warned...
BB
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On Tue, 11 May 2004 11:35:06 -0400, w_tom <> wrote:
From
Tue Jan 29 10:24:51 2002
Path: mindspring!news.mindspring.net!not-for-mail
From: Thomas D Horne <>
Newsgroups: alt.home.repair
Subject: Re: Help with grounded wiring in old house...
Date: Tue, 29 Jan 2002 10:24:51 -0500
Organization: MindSpring Enterprises
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References: <a31fs4$fq$>
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To: w_tom <>
Xref: mindspring alt.home.repair:427222
w_tom <> Wrote:
> Battery backup: many feel that plug-in UPSes always power directly
> from the battery. False. Most UPSes connect the appliance
> directly to AC mains when not in battery backup mode. It is why
> plug-in UPSes are so inexpensive. Furthermore, those $500+ UPSes
> that do power from the battery do not provide effective surge
> protection. Destructive surges are common mode (which is why earth
> ground is so critical). A common mode surge voltage appears
> equally across the battery terminals. IOW the surge not even seen
> by the battery continues down all wires, into the computer, and
> destructively onto earth ground. What kind of protection is that?
> Protection that is not even in the specs for that UPS.
>
> Where is that battery protection? It exists only in urban myths.
> Protection by the battery is promoted when the human does not
> understand the difference between common and differential mode
> transients. Surge protection adjacent to an appliance is for
> differential mode transients which typically don't exist.
Destructive
> transients are common mode which is why earth ground is so
> critical.
>
We did extensive testing of battery powered equipment at integrated
power corporation a decade ago. The common mode surges you speak of
never got past the rather massive capacitive effect of the wet cell
lead
acid batteries used in continuous duty UPS assemblies. These were
large
units that were capable of carrying the entire connected load for
several hours after supply power was lost. They did provide very
effective common mode surge attenuation and because they were always
connected via the battery the time to break over was zero. The
equipment used was high quality commercial stuff (trace et al) and the
test were done to validate radio relay sight power design. Test using
only one of the large twelve volt lead acid batteries showed very
favorable results. Since these power supply systems were built in the
early nineties they have suffered no surge or spike induced connected
equipment failures. These systems were installed on ridge lines and
mountaintops from Alaska to Argentina. The actual data is no longer
available because westinghouse closed that subsidiary when the tax
benefits of solar and wind energy died.
> A separate earth ground to the outlet safety ground is a code
violation.
>
This is not true. If the equipment grounding conductor to the
equipment
grounding terminal of the receptacle is installed in compliance with
the NEC(c) the installation and connection of a supplementary
grounding
electrode is not a NEC violation. It is only an NEC violation to use
the separate grounding electrode as the only equipment grounding
means.
The applicable portion of the NEC is;
["250.54 Supplementary Grounding Electrodes.
Supplementary grounding electrodes shall be permitted to be connected
to
the equipment grounding conductors specified in 250.118 and shall not
be
required to comply with the electrode bonding requirements of 250.50
or
250.53(C) or the resistance requirements of 250.56, but the earth
shall
not be used as the sole equipment grounding conductor.
Grounding electrodes, such as ground rods, that are connected to
equipment are not permitted to be used in lieu of the equipment
grounding conductor, but they may be used for supplementary
protection.
For example, grounding electrodes may be used for lightning protection
or to equalize potentials in the area of the equipment. Sections
250.4(A)(5) and 250.4(B)(4) also specify that the earth not be used as
the sole equipment grounding conductor or effective (ground) fault
current path."]
--
Tom