Guide to Electric Fence Selection

Guide to electric fence selection, including the fencer, how it works, set up, planning a pasture fence, wire, posts, installation, and hooking up the wire.


| May/June 1986



Cows electric fence

An electric fence consists of one or more strands of bare steel wire charged to deliver a convincing (but short-lived) electric shock when touched.


PHOTO: FOTOLIA/OLANDSFOKUS

Every country dweller occasionally has a need to keep some creatures in bounds and to keep others out. But all fences are not created equal. Wooden ones demand a lot of labor and maintenance. Barbed wire fences can injure animals (or installers). And welded wire enclosures are both expensive and unwieldy. The cheapest, easiest to put up, and most flexible animal containment there is replaces the pure force of a physical barrier with applied human intelligence and technology. I'm talking about electric fencing.

Selecting an Electric Fence

An electric fence consists of one or more strands of bare steel wire charged to deliver a convincing (but short-lived) electric shock when touched. You can rig anything from a one-strand rabbit barrier around the carrot patch to a "Down Under" multistrand, high-tension fence that carries enough voltage to keep a whole county of winter-hungry deer from your young fruit orchard. I'll tell you how to design, install, and maintain the electric fencing that's best for your place . . . or your places. That's another advantage of electric fencing: Country people do move from time to time, and electric fence is the only form of barrier that is readily transportable.

The Fencer

The heart of an electric fence is the charger, or fencer (See Figure 1 in the image gallery for the electric fence diagram)., which combines an electrical transformer with a timing mechanism to develop those short, sharp shocks. The current can come from a 6- or 12-volt DC battery, a small photovoltaic system, or from (greatly modified) 110-volt AC household current. The most persuasive chargers are the low-impedance "Energizers" used to electrify sheep fence by the hundred-mile leg in the Australian outback. These turn 110-volt AC power into pulses of 3,000 volts at 30 amps-almost a hundred thousand watts of power and enough to turn a whole herd of sheep into shish kebab were each pulse not limited to a few ten-thousandths of a second. The typical domestic line-powered charger develops only about 4,000 volts at half an amp. This two thousand watts is also a potentially dangerous charge, but each pulse (they come on 50 to 60 times a minute) lasts less than a thousandth of a second. Battery — powered fencers have less oomph behind them, so they release longer pulses — lasting about a half-second each — at a fraction of an AC unit's voltage.

The jolt from a typical fencer feels like you've been hit by a rapid-fire electric peashooter: brrrrrrrrrrrrrrrrrt. You feel it and pull back right quick, but there is no burn or lasting pain — just a strong and unpleasant memory. And since the current pulses for only a fraction of a second, there is little danger of getting "frozen" to the wire. I am told that a fencer shock can interfere with cardiac pacemakers and such; if she's so wired, forewarn Great aunt Emmie to unplug the fencer anytime she goes out to bust broncs in the back pasture.

You absolutely must use a UL- (or similarly) approved fencer to charge your fence. Such a device is effective and safe — it will blow a fuse instantly during any serious malfunction. Don't do as some neophyte homesteaders have done and wire an electric fence directly to a wall socket, welding transformer, model railroad speed controller, or any home-brewed device.

How an Electric Fence Works

You'll recall from junior-high science that electricity is the flow of free electrons from the + to the - terminal of a power source through a conductor such as metal (or a water-based living thing). The steel fence wire is good conducting material that's held away from any other conductors such as wood or metal fence posts by nonconductive ceramic or plastic insulators. The hot, +, post of the charger is connected to the fence. The other, -, post is wired to a stake driven into the soil. Normally then, each time the charger pulses with voltage, trying to send a charge of electrons through the wire, nothing much happens. There is no connection between the hot + post and the - return one, so there is no flow of current — no amperage. The circuit is open. Only when your curious saddle pony brushes the wire with his velvety muzzle does the circuit close (See Figure 2 in the image gallery for the electric fence diagram). Then a brief shot of current flows at lightning speed from the + post of the fencer . . . to the wire . . . through the pony's nose, body, and hooves . . . back through the soil . . . and to the - post of the charger. ZAP! The shock is delivered, causing the pony to pull away and reopen the circuit.

mike green
8/23/2012 5:56:19 PM

Love the in depth article. Another helpful source we found when installing our electric fence was the fence planner from Zareba. They help you map out the fence dimension as well as give helpful recommendations for what types of equipment to use based on the animals being contained. Check it out here: http://www.zarebasystems.com/resources/fence-planner






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