An electric fence is installed as an open circuit originating at the fence energiser, with current carried by the fence wire. When an animal touches the wire, the current flows through the animal down to the ground, to the earth rod and back to the energiser. For the animal to feel an effective shock, the earth system must be efficient enough to allow an unrestricted flow back to the energiser. Up to 80 percent of all electric fencing malfunctions are due to a poor earth.
Installing an earth
Work out how many earth stakes you need. Larger fence energisers exerting more power, or longer fence lines with higher leakage, require substantially more earthing. As a rule aim for one metre of earth rod for every joule of energy i.e. a five joule energiser will require five metres of earthing. Your earth stakes should be at least four metres apart. Link your earth stakes together using underground cable. Connect the last earth stake to the energiser’s earth terminal.
- Keep earth stakes away from domestic earth systems, and at least ten metres away from any other earth installations, i.e. those used by telephone or electricity supply companies
- Never use steel water pipes or steel framed buildings as an earth
- Don’t use copper wire or use copper as an earth stake
- Place your earth system in a consistently damp site. You can boost the efficiency of the stake by watering the ground in dry weather or increasing the number of earth stakes
- An earth system installed in winter, which is adequate for winter conditions, may not be suitable for dry summer. This may explain any substantial loss in power on your electric fencing over the summer months
- Use only our heavy duty or superconductive cable for energisers of more than five joules
Testing your earth
- Create a dead short on your electric fence line, at least 100 metres away from the earth stakes, by laying an iron bar across the wires to ground.
- Using a voltmeter, measure the voltage between the earth stakes and the ground. Anything above 200-300 volts indicates the earth is inadequate, and you should install extra rods at four metre spacing’s until the voltage comes back down to near zero.