graze-l May 2006: [SPAM] - Re: [SPAM] - Re: [SPAM] -
Re: [Graze-l] Grounding for electric fences. - Email found in subject - Email
found in subject - Email found in subject
To clarify:
The NEC is exactly correct on the 60 Hz grounding. This is the reason
that you will typically find 5/8" rods for sale at hardware and building
centers. Both theoretical and measured results confirm that this size is
optimum for 60 Hz.
As I mentioned earlier, this is NOT true for the faster rise time
transients that come from fencers (energizers) and, especially
lightning, that require better grounding options. Thus the use of
multiple rods to improve the ground for these higher frequency pulses
(often 100 KHz or even above 1 MHz).
You can use galvanized (zinc coated) rods which have the advantage of
lower cost and keeping the junctions the same if you use galvanized
(zinc coated) high tensile wire for the ground wire. Hot dipped
galvanized rod is being accepted now. This is a very recent change since
copper clad rods have been the primary requirement for something like 50
years. Both will work since the main purpose of the coating is to
protect the steel core.
In some cases where you have extremely difficult dry conditions, you can
use a stainless steel rod placed in a high salt/bentonite clay mixture,
but the reason for using the stainless metal is to prevent the severe
corrosion that would occur with most other metals or clad/galvanized rods.
Rick W.
leon wrote:
>On 15/5/06 1:55 AM, "KV9U" <mrfarm@mwt.net> wrote:
>
>
>
>>The size of most ground rods in the U.S. are based upon the efficient
>>grounding of 60 Hz AC from the power company. Anything larger in
>>diameter than around 5/8 of an inch does not increase the grounding
>>effect, thus the selection of that size by the U.S. NEC (National
>>Electric Code).
>>
>>
>
>They are WRONG when it comes to fencing. Remember apples with apples.
>
>60 Hz AC is a slow trickle of perhaps a millionth of the 5,000 volts and
>five or more joules in 0.0003 of a second. An old electric motor could
>increase the trickle when starting.
>
>In Holland the law was (in 1980s and I hope they�ve changed it) that only
>electricians could install the energizer and the earth peg which was 5/8
>diameter and one metre long - and that is all they installed. As soon as the
>electrician left most farmers would add to it. Working with electric fences
>from 1955 to 1987 I got many shocks, but the worst was when in Holland in
>1983 sorting out a problem for Gallagher. The farmer could not control his
>animals. While leaning on the iron shed I touched the silly little 5/8 earth
>peg a metre deep against a building so under the eve in dry soil. The
>building was a better earth than the peg so the power went through me. There
>was 3,500 volts on th earth peg. It should be zero or no more that 500 V.
>
>On our drystock farm of 107 ha with 107 paddocks (264 acres with 107
>paddocks 2.5 acres each) we erected 84 kilometres (52 miles) of two wire
>fencing (168 km of wire) and we used a disused 30 metre deep 4 inch diameter
>water pipe bore as the earth. It was perfect with no voltage on it at all
>which is rare.
>
>
>
>>The conductivity of copper is about 4 times that of zinc.
>>
>>
>
>The problem with earthing is not conductivity to the energiser, it is
>conductivity (contact or joining) from the soil to the earth stake.
>
>
>
>>Rick Williams
>>Misty Ridge Farm
>>Viroqua, WI
>>
>>
>
>
>Best wishes,
>
>Vaughan Jones
>Hamilton
>New Zealand
>
>
>
>_______________________________________________
>Graze-l mailing list
>Graze-l@witt.ac.nz
>http://graze-l.witt.ac
.nz/mailman/listinfo/graze-l
>
>
>This communication - including any attachments - may contain legally
privileged information, and is confidential to the addressee. If you are not
the intended recipient you should delete the communication and contact the
sender immediately. If you have received this e-mail in error, you must not
read, copy, disseminate, distribute or otherwise use or disclose any part of
this communication, or any information on matters or persons to which it
refers. WITT reserves the right to monitor all e-mail communications sent
through its network.
>
>
>
>
>
>
>
