“Amps kill. Amps hurt. So everybody wants lots of amps on their fence. That’s backwards. We want zero amps.”
– WIL REX
You don’t have to be Thomas Edison to build an electric fence, but it helps if you understand some of the basic principles of electricity.
According to Wil Rex, a dealer in New Zealand-based Gallagher fencing systems and components, many ranchers are willing to spend hours driving posts and stringing wires, yet fail to do their homework on electrical theory.
The first thing to remember is that a good electric fence, whether it goes around in a circle on a whole quarter section or runs in a straight line, uses almost no power.
With the red post on the energizer hooked onto the fence, and properly installed ground rods hooked up to the green, the electricity just sits in the wire going nowhere.
The cows don’t know it, but the fact that their feet are touching the earth means that they are already halfway to getting an invigorating zap.
“Wherever the cow wanders around, she’s alway hooked onto the green post on the energizer,” said Rex, in a presentation on electric fencing do’s and don’ts at a MAFRI organized pasture tour near Sidney last week. “The cow becomes the switch.”
When old Bossie touches the fence, she closes the circuit and gets a shock, just like your little brother would have if, say, you had tricked him into licking both terminals on the top of a 9-volt battery when you were kids.
But in the real world, nothing is perfect. Grass or stray wires may cause leakage in the circuit. To find them and get rid of them, a little gadget called a “fault finder” is handy.
Remember that voltage is a measure of electrical pressure, just like PSI in a water system, while amperage is the volume of electricity flowing through, much like gallons per minute.
“Amps kill. Amps hurt. So, everybody wants lots of amps on their fence. That’s backwards. We want zero amps.”
A perfect fence should read 7,000 volts and zero amps – high pressure, with no flow.
If the fault finder reads unusually high amperage, that means current is leaking somewhere to ground and a problem needs sorting out.
If the fault finder reading is between 5,000 and 12,000 volts, said Rex, that means there’s no problem to fix. A kilovolt, or one KV, is 1,000 volts.
“If you’ve got 5,000 volts on your fence, you’re good. If you’re running under 3,000 volts, you getting into where you’ve got poor livestock control.”
One thing the fault finder can’t tell you, is how many little faults may be adding up to big trouble. The only solution is to keep searching until they are all found.
Tall, wet grass – especially brome – can bleed a pile of electricity out a fence. The good news is that most cows, if they have been properly trained to respect wires, won’t start testing the fences until they run out of grass, he said.
To beat that problem, you can either put on a more powerful fence energizer to compensate for the losses – or build the fence properly from day one.
The best design, according to Rex, is to string three high-tensile wires on posts 45 feet apart. The bottom wire is stapled on 20 inches from the ground and the two others are strung each 10 inches higher up the post, for an overall height of 40 inches.
Doing it this way is quicker, saves a lot of money on posts and insulators and still provides a good barrier, he added.
The bottom wire, the one that is closest to the grass, is not hooked up, serves only as a physical barrier, and needs no expensive insulators. The top two wires are hot.
The next thing to remember, is to avoid cranking the wires up too tight.
“All you barbed wire guys, you tighten and tighten, then winter comes and the wire shrinks and breaks something. It either pulls the fence corners out or breaks the wires,” said Rex.
“Make your fence loose. With posts even at 30 feet apart, you should be able to step on the top wire and push them all to the ground. Relax a little, keep it loose.”
Besides making it winterproof, a loose fence means wildlife such as deer and elk will be able to blunder through it without breaking the wires, he added.
Ground rods are a critical point, and rust on them inhibits the flow of electricity. Sand or gravel which has had a good portion of its minerals leached out tends to act as an insulator because current travels via the minerals in the soil.
“Distilled water doesn’t conduct electricity,” said Rex. “You need water with minerals in it.”
Clay and loam, with lots of soil minerals, are best for electric fences. On very sandy soil or gravel, making a fence work effectively can be a challenge, he added.
Half-inch galvanized ground rods, six feet long are a waste of money, and even 5/8-inch rods 10 feet long aren’t much better. Those might last three years before the galvanized coating rusts away.
The best areW-shaped, because they offer more surface area and last from 10-15 years. Install one of for every three joules on the energizer under the fence in a straight line 10 feet apart.
“After five years, expect to put another ground rod in. And every couple of years after that, put another one in another 10 feet away. Just keep hooking them onto the existing ones, which are always going to work a little bit,” said Rex. “That’s what I recommend, rather than putting a whole bunch in the first year.” [email protected]