Fencing Management: Energizers

Table of Contents

1. Energizers
2. Grounding Electric fences
3. Testing For Sufficient Grounding
4. Wire
5. Number of Wires
6. Wire Spacing
7. Other Fencing Management Recommendations
   • Electrical Fencing
   • Posts, Insulators, and Gates
   • Regulations, Predators, and Maintenance
   • Protection From Lightning
8. Related Links

Energizers

There are many energizers (also called chargers or controllers) on the market. The type needed depends on the:

The available power source and power requirements determines whether a hydro, battery or solar unit is best. Hydro (alternating current) units are most effective and require less maintenance.

Energizers are often rated in miles of wire. A 10–mile unit will power 10 miles of single strand fence or 5 miles of double strand fence under no load conditions. Most fences run through bush and long grass. Under heavy load conditions a unit rated for 10 miles may be sufficient for 2 miles or less. Output joules more accurately estimates ability to carry current for a long distance. One joule for every 6 miles of electrified wire is a guideline.

Compare energizers based on cost per joule. The current that travels on the wire is measured in volts. Minimum voltage recommended for cattle is 2,000 volts, sheep 2,500 volts and horses 1,500 volts. All units need lightning protection against power surges on the hydro line and to be kept under cover from the weather.

Consider future needs when buying an energizer. Purchasing a unit larger than presently required may save buying another one later. Solid state circuitry and modular service boards make repairs easier. Check the guarantee.

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Grounding Electric Fences

It is extremely important to properly ground electric fences by attaching the ground terminal of the energizer to a ground rod or rods. This allows the current to make a full circle through the live wire to earth to the ground rod and back to the energizer.

Figure 5-2. An electric impulse travels from the energizer along the wire to plant or animal to ground, to ground rods and back to ground post on energizer.

One half–inch galvanized steel rods or 3 quarter–inch galvanized pipe work well. Where soil types allows, make your ground rod 6 ft or more. If more than 1 rod is needed, place them at least 10 ft apart in a triangle pattern. Connect rods with 12.5–gauge wire.

For best results place the rods into damp earth. Keep the energizer ground 75–100 ft from a hydro ground and lightning diverter ground. Use a heavy gauge wire at least 12.5 gauge from the ground rod to the energizer. Make sure all connections are clean and free of rust. Use the same type of wire metal to avoid corroding. Clamps should be tight. Most electric fence problems are a result of a poor ground.

Under dry conditions run 1 fence wire as a ground wire separated from a live wire by half an inch. This ground wire is connected to the ground post on the energizer. When an animal touches both a hot wire and a ground wire it completes the circuit. In this way the soil is not used to complete the circuit back to the energizer. This gives the maximum shock.

Testing for Sufficient Grounding

To test for sufficient grounding, operate the energizer and short out the fence by laying a number of steel rods (or T-posts) on the wires at least 300 ft away from the energizer. The voltmeter connected to a live wire should show less than 1000 volts. Take a reading between the grounding rod and the soil at least 4 ft away from the rod. The voltmeter should read less than 400 volts. If a voltmeter is not available, touch the ground rod with one hand and the soil with the other. You should not feel a current if the fence is operating properly. If there is a problem it is because more ground rods are needed, ground rods are too close or there is poor connections between wires and ground rods.  

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Wire

An energizer is only as good as the wire. Current on a fence can be compared to water in a pipe. The larger the pipe the more water it can carry. Larger wire has less resistance to the current. A 12.5–gauge wire has about 1/3^rd the resistance of a 16–gauge wire. This means it will carry the current a greater distance under similar conditions. The lead out wire from the energizer should be at least 12.5–gauge.

For permanent fences a high tensile wire lasts the longest. It withstands fallen trees or branches. Polywire, polytape, 14–gauge wire and 16–gauge wire are suitable for temporary fencing. This wire can be rolled up and moved with little effort, especially if insulated hand reels are used. Polywire and polytape are recommended for short stretches of fence. Both have high current resistance. Polytape is quite visible and recommended for horses.

A "Spinning Jenny" is very useful when stretching high tensile wire. It allows the roll of wire to feed out smoothly and avoids tangling. Wire tighteners help control wire tension. An electric fence does not require a lot of tension unless it is acting as a suspension type fence as well.

Number Of Wires

Depending on the type of livestock, use at least 2 high tensile, 12.5–gauge wires on permanent fences. One wire supports the existing rail or page wire fence, with the use of stand-off brackets. One or 2 wires are adequate for cross fencing.

Wire Spacing

One strand of wire 30 in. from the soil controls cows, yearling heifers and horses. Two strands at 18 in. and 36 in. from the soil are often used for cows with calves, young heifers and horses with foals. For sheep and goats a 3–strand fence at 9 in., 18 in. and 30 in. above the ground is effective.

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Related Links

... on forages and pastures, visit Forages and Pastures (OMAF)
... on weed control, order Publication 75 Guide to Weed Control: Forage Crops
... on agronomy for field crops, order Pub. 811 Agronomy Guide for Field Crops: Chapter 5 Forages
... on field crop protection, order Publication 812, Field Crop Protection Guide
... on livestock, visit Livestock (OMAF)

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