Your Interactive Fence
- Feb 1, 2000
Interactive is a common word in our language now. It means an immediate and personal response. You click--your computer displays a response. Your horse "clicks" an electric fence, and it shocks him. The interactivity cues the horse to respect the boundary you've set. A powered fence acts as a barrier to enclose animals. With electric current running through the metal in wires, tapes, or boards, your fence is active, rather than passive. Hot wire repels the horse. Through its power, it tells the horse, "Go away!"
Electric fencing is safe for the horse, despite the instant of pain the fence causes. Forget the dinosaur-strength fence in the movie Jurassic Park. Your powered fence delivers a shock that surprises the horse with an effective reminder. He remembers the pain and leaves the fence alone and thus remains safely contained within the enclosure.
Besides its effectiveness, the cost of powered fencing is low compared to passive fencing. For the fencing itself, typical costs run around 60¢ to $1.25 per foot for the multiple strands, or $5 a foot including posts. The fence's power source, a reliable fence energizer, will cost from $100 to $200. Average costs of electrical power range from 50¢ to $1.00 a month.
To purchase electric fencing, you don't need a degree in electrical engineering. However, understand that you'll play an active role in planning and maintaining this interactive fencing system.
An electric fence can serve as a perimeter fence on its own, or as an inner or top rail added to a traditional fence of wood, wire, or vinyl. In either configuration, the fence follows a post and rail design. A line of posts suspend one or more strands of electrified wire or webbing. (Some horsemen choose electrified metal boards.) The metal within rails conducts electricity.
The top strand should be about the height of a horse's withers, from 48 to 52 inches from the ground. The substance of wire or webbing requires some level of tension, to keep the "rail" taut so it remains straight and parallel to the ground. Most wire or webbing for electric fences is hand-tightened to a medium tension. High-tensile wire requires equipment to stretch it tightly.
For safety and high visibility, you can choose from wiring encased in vinyl polymer, as a braided rope, or smooth plastic cord. You can choose the more visible flat tape, also called webbing. The rope measures from three-sixteenths inch in diameter, with white plastic encasing metal strands or a cable. Tape consists of polyethylene yarns woven into a white ribbon. The ribbon contains metal filaments of copper or stainless steel wire.
As a reinforcement to an existing fence, you also can run a single strand of smooth, bare wire of steel or aluminum. Wire is measured by gauge, with the smaller gauge (usually 12.5 to 14) having the greatest strength.
Whatever wire choice you prefer, the line should be strong enough to remain straight and tight, yet give way in case of an emergency. Even a powered fence sustains contact--from animals, vehicles, or even tree limbs. Your horse can push into the fence by accident, if he loses his footing or gets shoved against the fence by another horse.
Manufacturers rate wire by break strength or break load. A strength of 600 pounds indicates that the wire will break at that amount of pressure.
Jim Nesmith of Safe-Fence explained, "You want a balance, so the fence isn't too light to take a hit, and yet not too strong so it cuts the horse's skin. In a tape, you want the tape and wire to break at the same time, so the webbing and the wire break at the same point." A wire that's stronger than the tape surrounding it can be exposed if tape breaks first.
Nesmith noted that stainless steel wire lasts longer. "There's no corrosion with stainless steel. Aluminum wire will oxidize and become brittle, so it breaks more easily. Tin and copper also oxidize, which inhibits electrical flow. Stainless steel may not be as conductive, but it stays the same."
See, Touch, Shock!
Because the fence is "alive," think of it as a system of elements. The fence charger sends electric current through the metal wire. The wire conducts the current in a constant flow above the ground in a complete, closed circuit.
When an animal standing on the ground
breaks the path of the current, volts of electricity flow into the animal and back to the ground. The animal grounds the fence. The amount of shock should be at least 700 volts, to penetrate hair, skin, and hoofs. An effective shock will be a minimum of 2,000 volts, or better at 3,000 volts.
What about the shod horse? Wayne Burleson, Certified Land Management Consultant from Montana's Range Management Services, explained, "Iron shoes increase the shocking/grounding power. More pain will occur to the animal."
The fence needs a ground system to complete its power. The charged wire is grounded. In a ground return system, the electricity finds its way back to and through the ground to deliver the shock. Grounding acts somewhat like an antenna under the ground, with ground rods conducting the electricity.
The charger is also called a fencer, energizer, or fence controller. It supplies the power to the fence. A single charger connects to the fence with a wire. With a good electrical contact, it sends current through the metal.
Look for a strong charger. A powerful one will warn the horse with an "aura," just before he touches the wire or webbing. You want the voltage to deliver an initial zap that cues the horse to back up, not push forward against the fence.
For tape or braided rope, use a low impedance charger. This type delivers a short DC pulse, and the short pulse won't burn flesh. It's safe for the polymer strands, and produces maximum power to control livestock.
Look for the charger's output. You'll see power measured in two ways: joules or miles. A joule measures the electrical energy by voltage, amperage, and time. A higher number of joules means more shock. The mile measurement shows the maximum length of fence the charger can power. For example, a five-acre pasture fenced in tape would use a charger capable of powering up to two miles of smooth wire. That charger would be about one joule in output. A longer fence, enclosing a larger area, requires a more powerful charger to send voltage through the circuit.
Besides AC input chargers, you can choose a solar-powered or battery-powered model. These store joules of power, but you must ensure that the power remains sufficient. In general, the solar model isn't as efficient as an AC one. You'll pay more for solar, and its components won't be as reliable. However, the big bonus is that you don't have to run electrical current to the fence if it is away from the barn or house.
The powered fence's wire runs through insulators secured onto posts. They keep the electricity in its circuit by insulating the post from the current. Most insulators are molded plastic.
Realize that you'll need to respect the fence yourself. If you touch the fence with your hand, leg, or head, you'll feel its power. Less body weight absorbs more charge, so humans feel more shock than horses do.
Warn other people about the fence, through verbal reminders and posted signs. Check with local government about any regulations affecting the use of powered fencing.
A fence operates correctly only when installed according to the manufacturer's instructions. First, determine the placement of the enclosure. With a new installation or complete replacement, you'll build posts and attach the strands. Components include posts for corners, ends, gates, and fencelines. You can choose from one to four strands of rope or tape.
Match your charger type to the wire you've chosen and the size of your area. Your electric fence shouldn't be located underneath power lines or transmission lines. Try to locate the charger and grounding system away from an electrical panel. Your charger does need to be close to an approved electrical outlet. (Don't expect to run extension cords to a charger.) Shield an AC charger from the elements, such as placing it under eaves or inside a building.
You'll probably build your fence as a rectangle, but you can add more than four corners to form a polygon. Each corner requires planning, as to turn 90 degrees means a special insulator that can handle the tension from both angles.
With these basics, you can plan the details. Look at the terrain. If you have changes in elevation, you'll need to plan the posts to keep the topmost electric line a consistent height off the ground. The consistency of soil also affects your fence's grounding, beyond the obvious challenge of post-setting. To "earth" your fence properly, the soil needs to conduct the electricity. Soil that restricts the flow compromises your fencing system.
Install proper ground rods, such as driving into the ground three rods of galvanized steel that are six feet long and 10 feet apart. The damper your soil, the more effective your grounding.
Next, choose the type of fence rails and match those to post material and shape. For example, you can secure insulators for tape onto wood, metal, or vinyl posts. Be sure to match the insulators' design, such as tensioners for tape, to the type of strands you'll use.
Plan the number, placement, and width of gates. Each gate will require a plastic gate handle. When closed, the current flows through the metal inside the gate handle. You can safely grasp the handle, unhook it from the anchor, and open the gate.
You'll set posts from eight to 25 feet apart, depending on the manufacturer's suggestions. Metal T-posts are inexpensive, although they require plastic safety caps or sleeves to protect exuberant horses from injury.
Make a bill of materials. Fencing companies supply formulas to help you plan the supplies you'll need. Some offer complete systems of components designed to work together. (You'll find that many manufacturers are foreign, such as from Canada, New Zealand, and France.)
Start at one end, and build your perimeter. If you start at a corner with a gatepost that holds a gate that closes on the right, build away from the post clockwise. You'd go counterclockwise if your gate closes left.
Setting new posts is the most difficult task. Treated wood posts, at least 4 x 4, handle the stress at ends, corners, and gates. With a tension system, you'll need to brace the posts at these stress points.
When setting wood posts, increase security by making your holes square. Set the post, then backfill with concrete. You're creating a stronger base for the posts that sustain the greatest stress.
Attach insulators and run the strands from post to post. Debbie Disbrow of Ramm Fence pointed out a common mistake with tape: "Don't allow the fence to bunch up within an insulator. If you feel the fence will bunch, take the time to put two tensioners." This arrangement will keep the tape flat within the tensioner.
Tighten your fencing according to manufacturer's instructions. The wire, braid, or tape must not sag, as loose wire can ground out the current in the fence at best or entangle the horse at worst. With some products, the manufacturer advises pulling the fence tight by hand. Others require the use of a ratchet device to achieve the correct pressure.
Disbrow cautioned against overtightening. "A strong, aggressive person can pull on the fence. If you pull the tape too tight, it can stretch, break the wires, and lose electricity."
Connect the power to tape through a tensioner or splice buckle. Power sent directly to the tape will burn the plastic.
With most horses, the first touch communicates the fence's message. You might want to introduce the fence's "bite" by releasing an already-exercised horse in the enclosure. Watch the horse's reaction before leaving him alone within the fence.
Maintain your fence for reliable performance. Realize that weather affects your fence's integrity. Strong winds can cause the strands to flap loose. Check that they remain secure inside insulators.
Sunlight bleaches and weakens vinyl polymer. Buy fencing with UV inhibitors, and look for a 20-year guarantee.
Lightning transmission through the power line can damage the fence. Burleson advised, "Unhook the charger completely during lightning storms, if it's handy. You can install a lightning arrestor system. This may help once in a while, but not all the time."
Vegetation should not touch the fenceline. Regularly trim trees, bushes, weeds, and vines to remove any contact and prevent the fence from grounding out.
Test the fence to verify its operation. With a voltage meter, you can measure the charge. (For those of you without a voltage meter, take a long stem of green grass, hold one end, and touch the far end to the fence. Then, carefully move the grass slowly forward across the electrified portion of the fence. As you get closer to the current, you will feel the "tingle" of the electricity in your hand.) If you need to troubleshoot the fence, try to isolate the reason. Manufacturers blame an inadequate ground system for most problems.
Finally, remember to turn the fence on. You can leave the fence powered during a rainstorm, and leave it on all the time so animals respect it continuously. A persistent horse might retest the fence with a whisker. Some horses can tell if the charger's not on, and will push against the fencing. A constantly powered fence also will deter outside animals from entering the enclosure, such as deer, coyote, or dogs.
About the Author
Award-winning writer Charlene Strickland lives in Bosque Farms, N.M. She has published 8 books and over 600 magazine articles, and is a member of the International Alliance of Equestrian Journalists.