horse fence

[Valley Farm Supply]

How to Select, Install Electric Fence
Advice from an electric-fencing expert on selecting and installing it
for maximum security and safety for your horse. Plus, a maintenance
checklist for you.
By Bob Kingsbery with Sandra Cooke

When you need to build a new fence or replace an existing one, there's
a major reason for using electric fence: Properly selected, installed
and maintained, it's the most effective way to safely contain your
horse. It's also economical and easy to install and maintain. Let's
look at the basic components of an electric fence and how to avoid
common problems.






Key Electric Fence Components
Charger. Sometimes also called an energizer or fencer, the charger
needs to be powerful enough to deliver a definite jolt when your horse
touches it, even when its current is reduced by vegetation touching
the fence line or (as sometimes happens) by moist, dewy early-morning
conditions.

Ignore chargers whose power is rated by miles; look instead for one
rated by joules, a measure of the oomph with which the charger is
pulsing its thousands of volts of current through the fence once every
second. One joule is a minimum rating for fencing that encloses up to
five acres, but I always recommend getting the most powerful charger
you can afford. A higher joule rating doesn't mean the fence's jolt--
which can't injure horses or other animals--will be harder or more
painful, but that it will be more consistent.

The difference in cost will be insignificant compared to the value of
your horses and your peace of mind; expect to pay $100 to $120 for a
good one-joule charger that plugs into an outlet in the barn or
elsewhere; six-joule chargers now sell for less than $200, a small
premium for peace of mind. (Worried about your electric bill? Fence
chargers use negligible amounts of power, whatever their rating.) I
recommend solar-powered chargers--about three times as expensive as
the plug-in type--only for paddocks where 110-volt power is
unavailable; as well as delivering relatively low power for their
cost, they're susceptible to failure.

It's possible to run insulated cable up to 1/4 mile from a charger to
the fence without significant power loss. Install the charger under
cover (except for solar-powered chargers, of course), where you can
check it easily during each day's routine. Most chargers have a light
that flashes with the electric pulse when they're plugged in and
functioning.

Ground system. This is a series of three 6-foot-long, galvanized-steel
rods pounded into the ground 10 feet apart and connected by insulated
cable (see below) to the "ground" terminal on the fence charger. (In
areas where soil is very dry, more than three rods may be needed.)
Assuming that you have a good charger, the ground system is the key to
your electric fence's effectiveness. If your horse touches the fence,
he feels a jolt only when the brief pulse of electric current that
goes through his body and into the ground is picked up by the ground
system and returned to the fence charger, completing the circuit. Be
sure to use a ground rod clamp to attach the ground wire as tightly as
possible to the rod, rather than just wrapping it around.


Insulated cable. The cable that carries the electric pulse from the
charger to the fence needs to be specifically for electric fence, with
insulation rated for up to 20,000 volts (most fence chargers emit from
5000 to 10,000 volts)--the same degree of insulation as on automobile
spark plugs. By using cable designed for electric fence, you avoid the
electricity leakage that results when you connect the charger to the
fence with heavy-duty household electric cable, whose insulation is
rated for only 600 volts.

When attaching the cable to the fence itself, use a connector clamp
rather than just wrapping the cable wire around the fence; cable
connected by wrapping comes loose more easily or loses power due to
oxidation or corrosion buildup. All fence manufacturers sell a
connector clamp designed to work optimally with their product. You'll
also need the cable to carry the electric fence current from one side
of a gate to the other: Connect all strands of the fence to the cable
on the side of the gate nearest the charger.

My preference is to then run the cable above the gate via an archway
high enough to safely admit horses and paddock-maintenance equipment,
but most people prefer to run the cable underground. That's fine as
long as the cable is encased in waterproof plastic tubing, plugged at
each end with silicone caulking and buried in an 18-inch-deep trench
to protect it from damage by hooves and equipment. On the far side of
the gate, use connector clamps to attach all strands of the fence to
the cable.

Cut-off switch(es). Save lots of extra steps by installing a
weatherproof knife-type cut-off switch (sold in the electric fence
section of farm stores) between the insulated cable and its attachment
to the fence, enabling you to turn the fence off without going back to
the barn to unplug the charger. I also like to install cut-off
switches on both sides of a gate--multiple cut-off switches allow you
to isolate sections of the fence for easier trouble-shooting.

The fence itself. Visibility is key to an electric fence's
effectiveness and safety. Materials such as 1.5- or 2-inch poly tape,
braid, rope or coated HT wire make the fence easy for your horse to
see and avoid. (Thinner fence materials such as poly wire or 1/2-inch
poly tape are suitable for temporary installations or as a "hot wire"
to keep horses away from solid fence; uncoated electrified wire--
although dangerous when used as a fence material on its own--can also
be used to protect solid fence.)

Choose a product with a long warranty (for instance, some fence
materials have a guaranteed lifetime of 20 years) and follow the
manufacturer's recommendations for number and spacing of strands. A
good general rule of thumb is four to five strands of fence, 4 to 4.5
feet high, for perimeter fences and three to four strands for interior
fences. Space the top two or three strands no more than 12 to 14
inches apart and the lower strands 18 inches apart, with the lowest
strand 18 inches from the ground to minimize interference by grass and
weeds.

Insulators. The type of insulator you need (to hold the fence material
on the post that supports it, while preventing the fence from
contacting any surface that will cause current to leak) is determined
by your choice of electric fence; most manufacturers market insulators
specifically suited to their fence products. In general, braid, rope,
and coated wire are installed on insulators that allow the fence to
slide through. To help prevent chafe and wear on a tape fence,
however, insulators need to be the type that clamps and immobilizes
the tape (especially important in windy areas), and to be installed
vertically on the fence post. Avoid cheap "generic" insulators (often
made of brittle plastic), which only last a few years.

Testing, Testing... Why It's Important
When your electric fence is built, monitoring its voltage regularly--I
recommend daily--is a basic management practice, just like checking
water buckets. Use a digital voltmeter that tells you exactly how many
volts of current are on the fence. (How many volts are enough? Four
thousand to 5,000--remember, there's no way this jolt of current can
hurt your horse, but it needs to be definite enough for him to
remember it and want to avoid it.)

Your first check of your new fence's voltage gives you a baseline so
that future checks can alert you to voltage drops that signal
problems. Depending on the strength of your charger, it will emit 6000
to 10,000 volts when nothing is connected to it. After you've hooked
it to your fence, check the voltage at the furthest point from the
charger. Some drop in voltage--1500 to 2000--is normal. A more than
2000-volt drop means either your charger is underpowered for the
fence, vegetation or something else is "loading" the fence (touching
it, causing voltage to leak away), there's a short-circuit somewhere
in the system--or a combination of these.

If the base voltage on your newly built fence is 4000 or better and
everything's working fine, watch on subsequent checks for an overall
voltage drop of 1500 or more. (It's normal for voltage to be 500-1000
lower in the morning when moisture on the fence, posts, and nearby
vegetation can cause temporary current leakage.) Such a significant
decrease means it's time to check for problems and correct them before
your horse discovers the fence no longer packs a punch; in fact, many
horses can sense when the fence is or isn't functioning.



Electric Fence Maintenance Checklist
Look for and remove sources of "load." Mow or trim under bottom strand
to prevent grass and weeds from touching the fence; watch for fallen
limbs or other objects on the fence or caught in insulators. (Tips:
Listen for the rhythmic snap that indicates a voltage leak; follow
your ears to find the source. Drag a long stick on the ground beneath
the bottom strand as you walk the fence-line; it may knock away an
interfering object you don't even see.)
Check insulators. A broken insulator can allow the fence strand to
touch the post--not an immediate problem with a nonconductive wood
post, but if you're using steel T-posts a broken insulator can cause
the fence to go dead when the strand touches the metal.
Check connections. Ground-rod wires can get knocked or kicked away.
Wires attaching the cable to the fence may come loose.
Check the charger. A spider's web built between terminals can cause it
to spark.
Check insulated cable. Look for places where the cable may be abraded,
for instance where it passes through a hole cut in metal barn siding.
Check fence strands: Look for frayed spots in poly tape--if metal
fibers in the weave become separated, tape can't conduct current.



Texas-based international fence authority Bob Kingsbery grew up on a
family-owned horse-breeding farm; he has written widely on electric
fencing and has conducted more than 300 seminars on fence technology
and grazing management throughout the world. You can reach him with
your electric-fence questions via email at b...@kingsbery.com.

This story originally appeared in the March 2004 issue of Practical
Horseman magazine.