From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Campground observations
Date: Mon, 09 Jul 2007 20:05:43 -0400
Message-ID: <kti593pebf6rrvkg8k62pscds5j8hip1n9@4ax.com>

On Mon, 09 Jul 2007 15:12:23 -0700, Ben H <benhogland@hotmail.com> wrote:

>On Jul 9, 3:06 pm, "Kevin W. Miller" <i09...@strudelyahoo.com> wrote:
>> Lon VanOstran wrote:
>>
>> <snip>
>>
>> > I would water a ground rod which was not grounding, in an attempt to
>> > improve it's conductivity.
>>
>> > Lon
>>
>> How do you know that the rod is not grounding?
>
>A little testers like this http://tinyurl.com/2yfevr or a tester like
>a GoodGoverner.

That tells you nothing about the state of the earth ground.  The "ground" is the
copper path back to the transformer center tap.  Most earth grounds are simply
worthless feel-good window-dressing.  Few are of low enough resistance to conduct any
significant current to "ground".


I have a (very expensive) Biddle ground resistance tester.  This unit actually
measures the ohmic quality of a ground.  I've never seen a ground rod that hasn't
been watered or is sitting in water go much below an ohm of resistance.  Very simple
math shows that this would not be capable of tripping a main breaker if the line were
to be connected directly to the ground rod.  Since the secondary of a pole pig is
isolated from the grid, the value of a ground rod is tenuous, at best, and relies
heavily on the conductivity of the utility ground on the pig.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Campground observations
Date: Mon, 09 Jul 2007 21:33:48 -0400
Message-ID: <j7o5935v50hprblaib81lhrpdl0799lfcg@4ax.com>

On Mon, 09 Jul 2007 17:41:20 -0700, altar nospam <altar@nospam.net> wrote:

>At the risk of getting flamed, I think you guys are a little anal
>retentive about this. My guesstimate is that 95+% of all RV'ers
>couldn't tell you what a ground is, why you would need one, or care.
>
> I'm also guessing that the incidents causing harm every year due to a
>less than perfect ground could be counted without a calculator. I've
>got better things to do than worry about a ground wherever I go.

I pretty much agree.  About the only thing a ground rod MIGHT do is save the blue
smoke in the event the neutral back to the pig opens.  Some utilities seem to have a
chronic problem with open neutrals, including one of my clients.  When the neutral
opens, the side of the line with the most load gets low voltage and the other side
high.  A ground rod, if it's in conductive ground and properly installed, may conduct
some of the neutral current, mitigating the voltage excursions.  I'd not bet any
money on that happening, however.  Most earth grounds are simply window dressing,
something to make the inspectors feel good.

John

From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Campground observations
Date: Tue, 10 Jul 2007 15:10:30 -0400
Message-ID: <cam793hofsjoj8791ubn0a2nspmo891agp@4ax.com>

On Tue, 10 Jul 2007 08:16:38 -0500, "Ron Recer" <ron48@aol.com> wrote:


>Don't just check the voltage once and assume it is good.  We once left a
>park after a half hour or so stay.  Within that time the voltage went from
>fine up to 130 volts (the max my wall plug meter shows) and down to 100
>volts.  I couldn't get unplugged from their electrical service fast enough!
>Fortunately, nothing was harmed by the high and low voltage.

That is EXACTLY the symptoms one sees when the utility neutral opens up.  The earth
grounds probably kept it from swinging rail to rail (0-240) but they didn't stop the
excursions.

John

From: John De Armond
Newsgroups: alt.energy.homepower
Subject: Re: Home Electrical Grounding
Date: Sat, 13 Oct 2007 12:04:21 -0400
Message-ID: <soo1h3lt52intn7rnnku7idrhlai34mgtr@4ax.com>

On Sat, 13 Oct 2007 05:24:40 -0500, "Ken Maltby" <kmaltby@sbcglobal.net> wrote:


>> Service entrance ground rods are simply an anachronism that is little more
>> than for show.
>
>  "The requirements for all types of grounding are
>covered in article 250 of the National Electrical
>Code (NEC).  It is mandatory from both a legal
>and safety standpoints that all systems be grounded
>according to these rules."

Legal?  Perhaps.  Safety?  Not hardly.

>
> While there are conditions where a ground rod is
>less effective, in almost all circumstances it is more
>than sufficient to insure that fault currents will trip
>breakers and/or blow fuses.

Funny to watch someone make a fool of himself pontificating about something of which
he has no knowledge.

I deal with grounding systems that HAVE to be good (utility substations and
transmitter ground planes, for instance) and own a Biddle ground resistivity bridge.
I have just a little actual experience in the area.

It's VERY unusual for a single ground rod in dry soil to dip below 1 ohm. Given that,
let's do a little math.  Let's assume one ohm.  Let's also assume a bolted short
between a hot leg and the ground rod.  That would be 120 volts across one ohm which
would produce 120 amps of current through the 200 amp main breaker.  For a short
period of time until the heating dried the soil around the ground rod.  120 amps
being less than the 200 amp rating of the breaker, no tripping occurs.

But it gets worse.  The secondary of the utility transformer is isolated.  The only
connection to earth is, you guessed it, through another single ground rod.  Now the
circuit resistance is at least 1+1=2 ohms plus the minor resistance of the
conductors.  The bolted fault current is now 120/2=60 amps.

What happens is the earth around the ground rod is heated by the initial current
flow, is dried further, the resistance climbs and eventually an equilibrium is
reached where there is but a small current flow and the ground rod is at 120 volt
potential.  Feel free to experiment in this area.  You might learn something.

In reality, of course, the neutral conductor carries the fault current with a
resistance of a milli-ohm or so.  The very high fault current trips the breaker
almost instantly and all is well.  The ground rods did not participate in the
evolution.

If you're actually interested in learning something about grounding (and can read at
that level), might I suggest any of the following:

* Power System Grounding and Transients
* Getting Down to Earth... A Manual on Earth-resistance Testing for the Practical Man
(Electrical Grounding Systems, Earth Resistivity) by James G. Biddle Co.
* Army Corps of Engineers SuDoc D 103.53:M-89/12
* IEEE "Green Book"

These are the essential part of my library on grounding.

>>>Check your insurance policy but you are most likely now
>>>uninsured and will remain so until your home is properly
>>>grounded.
>>
>> Nope.  No more than if the ground were to become ineffective through
>> inadvertent damage, corrosion, ground clamp loosening or merely dry
>> ground.
>>
>
>  Check the fine print, generally the insured property must
>continue to meet all safety related building codes.

More bluster and arm waving.  Cite me any specific language to that effect.  There
has never been any such language in any state I've ever lived.  I doubt that there is
in any state, since such phraseology would serve as weasel words to let the insurance
company to get out of almost any claim, as some sort of code violation is present in
most any structure.

John

From: John De Armond
Newsgroups: alt.energy.homepower
Subject: Re: Home Electrical Grounding
Date: Mon, 15 Oct 2007 23:24:40 -0400
Message-ID: <dfb8h313kb7tvlsemo6po4l0jkjbd0d79u@4ax.com>

On Mon, 15 Oct 2007 10:42:07 -0700, "Bob F" <bobnospam@gmail.com> wrote:


>Let me ask you a question about ground rods.
>
>Where my house is, the water table seems to be about 7-10 feet down in a sand
>layer on top of hardpan about 17 feet down. Would a 20 foot length of 3/4"
>galvanized pipe driven down to that hardpan make a significantly improved ground
>over the 8 foot rod that is already there? Would adding it improve the
>usefulness of adding a whole house surge arrestor?

With a water table that high, the dirt around the 8 ft rod should be very conductive
as it is.  I don't think that anything any deeper will help.

For surge arrestor grounding, the AC impedance matters as much as the DC resistance
because the surge front is composed of much high frequency energy.  Getting the
impedance down involves distributed grounding and large conductors.  A standard
format low impedance ground can consist of 3 8' rods driven in a triangle, separated
by at least 8' to the side.  Connect these together, preferably with braided copper
strap, and connect the surge suppressor to that.  If you can't do a triangle, such as
along the side of a house, then three rods in a row with the same separation are
almost as good.

John