Re: Ground Rod For House ?
- From: "Pop" <nobody@xxxxxxxxxxxxxxxxxxx>
- Date: Sat, 31 Dec 2005 20:37:44 -0500
Mercy! I'm not quite sure what you're trying to say here, or
what the point of some of the irrelevant URLs/comments might be,
but ... either you need to step back and put your heard around
this again, or seek further education and experience.
You'll probably object to my post here, but it's so typical of
many on this group lately that I just can't hold it in any
longer. Those who have nothing to say, should say exactly that.
Those who do have something to say, should be clear and concise
about it. Rationalization and guessing have no place in the
realm of safety.
"w_tom" <w_tom1@xxxxxxxxxxx> wrote in message
news:43B6F1BC.25524FB3@xxxxxxxxxxxxxx
: Water pipe makes a good low resistance ground. Human safety
: demands a low resistance ground for reasons that include, for
: example, neutral wire failure.
===> Water pipe does not make a "low resistance" ground. It
makes a "ground", period. The word "low" must have a contextual
reference to be meaningful and there is none there. Besides,
it's not resistive; it also contains a reactive component,
sometimes surprisingly large.
:
: Transistor safety uses grounding components for a different
: purpose.
===> What is "transistor safety"? That makes no sense. You
apparently mean protection, as in protecting semi-conductor
devices from overvoltages. Further, you will find nearly no
transistors used anywhere these days in current designs.
Semiconductor, yes; transistor type semiconductors; pretty scarce
these days.
.... Transistor safety requires a low impedance ground.
===> No, it requires a stable reference w/r to the rest of the
ckt.
: If connecting a bonding wire to a water pipe 50 feet away, the
: house has a low resistance ground and a high impedance
: ground.
===> Resistance or impedance? Are you using these
interchangably? They are two entirely different things.
Impedance would be the term you need here as the reactive
components are substantial.
High impedance means ineffective transistor
: protection.
===> Now you've switched from safety to protection. Which is it?
What high impedance are you talking about?
Take this fax machine protection as an example:
: http://www.epri-peac.com/tutorials/sol01tut.html
:
: Unfortunately AC electric and phone service enter on two
: sides of the house - bad construction practice.
===> Bad assumption: that's a schematic representation, not a
bad construction practice, and the only thing you can discern
from it is the marked distances indicated for wiring.
If 'pictured'
: water pipe is a significantly lower impedance connection, then
: a destructive transient will find the building's single point
: earth ground via NID (surge protector)
===> NID is NOT a surge protector. NID is the Network Interface
Device, and PART of it is surge suppression, NOT for any purpose
other than protecting the demarcation point connections at a 600V
clamping voltage. YOu've mis-assumed some things there.
and cold water pipe.
: But in reality, cold water pipes are typically too long, too
: many solder joints, too many sharp bends, etc.
===> Sharp BENDS matter to resistance/impedance? I don't THINK
so! What are you worried about, the kinetic energy of the moving
electrons going around a corner where centifugal force slows them
down? I hope not!
You don't understand conductivity, I'm afraid. You're just
parroting and trying to justify something with rationalization.
It doesn't work.
To connect to
: a common point, an additional wire that is not shown.
All
: increase impedance so much that a transient will also seek a
: destructive path to earth via the fax machine.
===> A "transient" will NOT seek a "destructive" path to earth.
It will seek the path of least resistance to current flow whether
that consist of pure resistance (it doesn't) or either of the
reactive elements. Another way to state it is, it will seek any
potential lower than itself in magnitude. That includes ac
characteristics, by the way.
Incoming on
: phone line. Outgoing on AC electric wire. Fax machine
: damaged because NID was not earthing via a low impedance earth
: ground connection.
===> NO ELECTRONICS are protected, nor are they intended to be
protected by, the telco surge suppression components, which are
often arc-over devices or gas tubes or carbon stacks.
:
: This demonstrates but one example of how portable phone base
: stations, fax machines, and modems are so easily damaged.
===> It does indeed, but it does so because there is no
protection afforded to, nor intended to be afforded to,
electronic equipment by the telco protectors. You've completely
lost track of what a ground reference means in these contexts.
Or, don't know what it means.
: Essential to transistor protection is a connection from each
: incoming utility, either through a protector or by direct
: hardwire, to a common earth ground connection. Single point
: earthing most easily accomplished with a ground rod wired
: short (ie. less than 10 feet) to AC electric box. For
: transistor safety, all incoming utilities (telephone, cable
: TV, satellite disk) must make a less than 10 foot connection
: to this common earthing point.
===> It's obvious you've been reading, but ... you're not putting
things together correctly.
:
....
: A most common source of transistor destructive transients to
: things such as computer modems is incoming on AC electric.
: Wires highest on poles - AC electric - are more often struck;
: not lower cable and phone line. If that 'arrestor' does not
: connect AC electric wire to earth ground, then a transient
: (again in that picture) goes into fax machine (modem) on L
: connection, then destructively out on phone wires to NID and
: to earth ground. Above demonstrates why fax machines, modems,
: and portable phone bases stations are so often damaged by AC
: electric wire transients.
===> Wow, those are some huge assumptions and incorrect at that.
That come nowhere close to explaining why fax machines etx. are
so often damaged by electric wire transients. In reality, if you
research for facts just a little bit, you'll find that most
telephone appliances are damaged by transients because they have
NO protection, or under rated protection.
Lightning is NOT the overwhelming reason for damage to those
components. Lightning is one of the least controllable damage
elements in existance. You can only partially protect against
small, almost tiny lightning hits.
Most transients are generated from other sources, the majority
of them being inductive loads, grid controlling elements in the
ac plants, transformer problems, and even the loads and motors
within a building itself.
I don't object to someone trying to help things out; I do object
to obvious rationalizations and attempts to justify things to
one's own "feelings" of how something should be. The world just
isn't'' like that.
:
: Above is pre-WWII technology now made necessary in dwellings
: due to something new - transistors. Transistor protection is
: often little understood by some electricians who only
: understand NEC requirements.
===> NEC requirements have NO, nada, zero, consideration for the
protection of semiconductor devices and thus is of no concern to
"some electricians". I do think though that you're on shaky
ground by saying they have no understanding - many actually do.
NEC does not require transistor
: protection. NEC is for human protection. Transistor
: protection is defined by the most critical component in a
: protection system: earth ground.
===> Oh, gosh, no. Earth ground has almost nothing to do with
the actual protection. It's the RELATIVE electrical position of
the references, whether it be a dc voltage, 0 volts, or even a
high voltage, that matters. I can run a 3 Volt microprocessor on
a 100V DC line if the other side of the line stays within 97
volts (or 103 as the case may be) of whichever is determined
(chosen) to be the reference. Yes, 100V DC CAN be considered
GROUND to a ckt and everything will work fine, including
component protection against transients. Actually, you could
look at some TV schematics to get an idea of how some of that
works.
:
: Gfretwell has posted how homes are now being built so as to
: provide superior transistor safety in pictures at:
: http://members.aol.com/gfretwell/ufer.jpg
:
: Another also demonstrates better earthing. None of this
: would be required if city water pipe was sufficient as earth
: ground for transistor safety:
: http://www.knology.net/~res0958z/
===> Noo, that's NOT the reason water pipes aren't allowed as
ground any longer. Actually, transistors being as old as they
are, they were quite well protected by cold water pipes and the
same standard surge protection used by many people today. That
changed when it was no longer allowable to use water pipes for a
safety earth, and as I've tried to indicate, it is almost a moot
point to anything.
You will still find many thousands of homes with water pipe
grounds, with modern electonic equipment that works very well and
just as well as any other system you can imagine.
:
: Above was earthing for secondary protection. Also necessary
: is earthing for primary protection:
: http://www.tvtower.com/fpl.html
===> I don't think you have any idea what primary and secondary
mean here, do you?
Enough soap boxing, I guess. I don't have anything else to say
on the matter, so that is what I'm going to say.
.
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