Electric fence, including danger

If mainline power is available and dependable, 110 or 220 volt AC (plug it in the wall socket) energizers are usually most practical for permanent fences. Will they raise your electricity bill? Well, depending on the size of the unit, they typically draw 2 to 25 watts. The operational cost of an energizer drawing 17 watts would be about $1.50/month (assuming an electrical rate of $0.12/kilowatt hour).

How dangerous are they? Energizers (chargers) are usually rated in “joules.” (pronounced the way a West Virginian pronounces jewels.) This is a physics unit for measuring energy. It is directly related to the “kick” the fence gives the animal (and human) that shorts it to the ground. My daughter worked in the cardiac care unit of Ruby Memorial Hospital at one time, so I asked her how many joules were used to revive someone whose heart had stopped. She said 450 joules. So I don’t think there is much danger of heart stoppage with a properly grounded commercial charger. But 4 or 5 joules from the fence will “really get your attention,” as they say. I know, because I have been hit many times.

At this point I need to introduce a couple of terms. A capacitor (also called a condenser) is a device for storing electricity. That’s what a battery does, too, but the capacitor is able to let its contents go almost instantly, were a battery stores a lot of electricity and takes some time to let it go.

Volts is a measure of how hard the electrons are pushed through the wire. The more volts the more electrons are pushed through a particular resistance (the animal, or you, if you are not careful).

The way a fence charger works is to take 110 volts (or 220 volts if so wired) off the high line, step it up to several thousand volts to load the capacitor (sometimes more than one) in the charger. This takes about three-quarters of a second, then it switches that line off and hooks the capacitor to the fence. When this happens the fence shares the load with the capacitor. At this point the fence should read a few thousand volts on your meter.

That sounds pretty scary if you don’t know the details. The function of the capacitor is to limit the number of electrons at this high voltage. That much voltage off the high line would “fry” you. In fact, 110 can fry you too, if you are sufficiently grounded so the current of electrons can flow through you. The high line is effectively an unlimited supply of electrons.

The charger lets the charge on the fence drain off to ground within a few thousandths of a second after it starts. The intermittent nature of the charge on a proper electric fence is an important safety feature. Most of the time there is no charge on it, just very briefly for a few thousandths of a second about every three quarters of a second. The intermittent nature of the shock increases the element of surprise too, increasing its effectiveness

If there are weeds on the fence, they drain off the electrons, and so reduce the kick. Fortunately, their resistance is rather high, so some weeds can be tolerated. You need to keep the bottom wire about 17 inches or slightly more above ground, so cattle can eat under it, which helps keep the weeds down. It pays to have the area under the fence properly limed so you have palatable grass there, too.

The resistance in the “voltmeter-fence tester” is very high, so not many electrons drain through it. It does not “short out” the fence.

A good ground for the energizer (fence charger) is important. It will interfere with a telephone cable for several tens of yards. Be careful where you place it. The standard grounding rod, half inch in diameter and six feet long works well. It needs to be down to moist ground, no matter how dry the surface is. The dryer the surface is, the more kick you need in your fence. The rods are made so long to get down to moist earth. Use a steel fence post driver of the type that is a tube with handles on each side to get the rod down as far as you can, then use a sledge hammer. The preferred method is to take it below the surface, and use a clamp to attach a large diameter copper wire, which is also kept below the ground to where it can go straight up to the charger. Use several, preferably four hooked up with the same large diameter copper wire as the first one. Steel fence wire should not be used, particularly below ground – it rusts.

Insulators are made for steel posts, but steel posts should not be considered permanent. You find this type of insulator at feed stores. They soon age. Use treated wood for permanent posts, or locust. Locust serves well if you can find good trees, with no fungus infected wood. Both locust and treated posts have considerable conductivity, so insulators are needed. Get polyethylene or polypropylene plastic insulators. Also don’t use fine wire for permanent fence, deer will break it in no time.

Use “string fence” with polypropylene cords and fine stainless steel wires woven in for temporary fence. Just tie it for connections. Use lots of wrapping in your knots so the tiny stainless wires will come in contact with the steel wires. Get good spools to wind it on, ones designed to roll up extension cords. Take care of it, and it lasts for years. Don’t use the fancy plastic fence posts for permanent fence, they age very fast, and you can’t keep the wires tight. If you plan to reuse temporary posts, get fiberglass. I have used some for ten years. I like three-eights inch round posts which you can get from some fence supply houses and add two adjustable holders for the string fence. This is called “Spider Fence.”

An electric fence is not a physical barrier, like barbed wire and woven wire. It is psychological fence. Animals avoid it, but learn to eat inches from the wire. Animals unfamiliar with it can stumble through. Under extreme conditions predators can drive them through, and baby calves do not understand it the first time they come in contact. They seldom go through twice.

We keep a road wide enough to run a four wheeler along the fence through the woods and where ever we can. Like any fence, they need to be checked often. The four wheeler makes checking fast and makes access for the few needed repairs easy. We keep a few tools with us on the four wheeler any time we go into the pasture so that repairs can be made without a return to the house for tools.

Finally, the electrons repel each other, because they have negative charge. Most of the charge when it moves is carried in the outside layer of the wire. Rust is an insulator compared to the steel or its zinc galvanizing. Wire needs to be changed when it guts rusty. An electric fence will last far longer than barbed wire, though.

Some don'ts for electrical fence: 1. Don’t hook to the high line directly, without a charger. In other words, don’t provide the legal profession with another lucrative case to litigate at your expense. 2. Don’t use barbed wire. The animal needs to get away from the fence. 3. Take the time and go to the trouble to build a good ground. 4. Don’t get cheap plastic stuff. The insulators sold by fence supply houses have additives which make the insulators last and last. 5. Don’t use metal posts for permanent electric fence.