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Your earth system is the most important component of your electric fence. An effective earth system will optimise the performance of your electric fence.
UNDERSTANDING EARTHING
What is an earth system? The earth system consists of a number of earth rods the provide an effective (low resistance) path for the current to return to the energizer's earth terminal. Larger energizers with large fence lines require more earthing rods.
How does earthing work? For an electric fence shock the current produced by an energizer must complete a full circuit. The current leaves the energizer and moves along the fence wires through the animal, into the soil and back to the energizer via the earth system. If the earth system is ineffective the animal will receive an inadequate shock.
What factors affect your earth system? Dry, sandy or non-conductive soil (e.g. volcanic soil) provides and ineffective earthing system. If you have this type of soil, it's a good idea to 1) use additional earth rods or 2) choose a better location for the earth system (such as damp soil) or 3) consider an alternative method of earthing such as the Fence Wire Earth Return.
Setting up your Earth System
STEP 1. CHOOSE THE RIGHT SYSTEM FOR YOU
Option 1: Ground Earth Return System. Recommended where soil is conductive. This system is suitable for most moist soils.
Current flows through the animal and the ground back to the earth rods.
Option 2: Fence Wire Return System. Recommended where soil is not conductive. If the soil is dry, sandy or volcanic it is usually not conductive.
The fence is constructed using both live and earth wires. If the animal touches the live wire the current flows through the animal and the ground back to the earth rods.
STEP 2: SELECT THE SITE FOR YOUR EARTH SYSTEM
A suitable place for an earth system is:• At least 10 m away from other earth systems e.g. house mains, underground power or phone lines
Away from stock or other traffic that could interfere with the installation
Easily accessible for maintenance
Where there is damp soil all year round (e.g. shaded or swampy areas)
STEP 3: INSERT THE EARTH RODS
The number of earth rods required depends on the type of energizer you're using to power the fence and the soil conductivity. It is recommended that you consult with your local Tru-Test Group Area Sales Manager or Speedrite retailer/distributor for the correct number of earth rods for your specific location.
Space the required number of 2 m earth rods at least 3 m apart. If using a bentonite earth system, space the rods at least 10 m apart
Ensure that the earth rods protrude out of the soil by 100 mm so they can be easily connected
Connect the earth rods in a series using joint clamps and insulated cable* in one continuous length without joins
*Note you will need to strip small sections of the insulation away from the cable to connect the joint clamp/earth rod.
STEP 4: TEST YOUR EARTH SYSTEM
Test your earth system to ensure it’s working properly. To do this:
Turn off the energizer.
Short circuit the fence to ground at least 100 m away from the energizer. This can be done by laying steel rods or pipes against the fence. In dry or sandy soils, drive the rods into the soil up to 300 mm.
Turn on the energizer.
Use a digital voltmeter to measure the fence voltage. It less than 2 kV. If not, repeat steps 1 - 3 using more steel rods or pipes against the fence.
Attach the voltmeter clip to the last earth rod of the earthing system.
Insert the voltmeter probe into the soil at the full length of the leads.
The voltmeter reading should be no more than 0.3 kV. If the reading is higher than this, the earth system is inadequate.