Setting up the electric fence unit by the book is the best approach to ensuring the fence will work to its potential. An electric fencer works by converting electricity into a high-voltage pulse. This high-voltage pulse is connected to an electric fence line which is a conductive wire. If an animal touches the wire, the pulse will run through the animal and into the ground.
All electric current wants to get back to source. Therefore, power on the fence wire needs to get back to the fencer via the earthing system. If an electric fence touches an uninsulated wire, eg sheep wire, or a lot of vegetation such as nettles, thistles or earthed material, almost all of the power pulse will be drained from the wire and the shock felt by the animal will be minimal.
Figure 1 above shows how an electric fence works. The fence unit connected to a wire on its own is useless without a properly functioning earthing system. Padraic George explains the process involved in setting up an electric fence unit properly to the Irish Farmers Journal.
1 To set up the earthing system you will need 1m-long earth bars, each driven fully into damp ground and spaced 3m apart. The number of bars required depends on the size of the fencer and the type of soil.
Stoney ground requires more earth bars. Here is a guideline for the number of bars required:
The earth system should be positioned 100m away from any other earthing system. Damp ground is preferable as it will be a better conductor of current and should result in the fence giving a better shock. The wire to connect to the earth system should be steel to match the metal type of the earth bars. Using copper wire here joined to galvanised mild steel earth bars causes corrosion at the joint.
2 Using a carpet knife, strip back enough of the insulation coating on the wire so that there is enough available for good contact with the earth bars.
Padraic says it is best to put down the last earth bar first and tie the cable to it before moving on to the next one. There should be about 3m between each earth bar. There is no need to cut the wire for the bars in the centre. Instead, Padraic strips off a section of insulated coating and loops the wire around the bar. Steel clamps are then used to hold the wire securely to the bar.
3 Now it is time to set up the fencer. The fencer should be located inside in a dry area and near a power source. The cable from the earth system should be connected to the earth terminal, which is normally green on fencer units.
Try to ensure good contact between this wire and the earth terminal and use the screw clamp provided to secure. Black, yellow and red terminals are for the fence line. They stand for low, medium and high voltage. Choose the terminal best suited to the fence line (usually farmers will choose the red terminal or high-voltage terminal for greatest output).
4 The lead out cable should be sized appropriately to the dimensions of the fencer. Double-insulated 1.6mm steel wire is used for the 50-acre and 100-acre models, while double-insulated 2.6mm steel wire is recommended for 200-acre and 300-acre models.
Use double-insulated underground cable at gateways to ensure the fence line power is continuous around your farm. Run this cable through a water pipe to further protect it in the ground.
5 Padraic has a useful tip for farmers who want to double check that their earth system is working sufficiently. All you need is a steel bar and a volt meter.
First, turn off the fence. Next, drive the bar into the ground and push it against the electric fence line. Turn on the fence again. All the current should now be draining from the fence line, through the bar, into the ground and heading straight back to the earth system. Padraic says to measure the voltage between the last earth bar and the ground, this needs to be less than 500v, indicating your earth system is good. Greater than 500v and more bars are needed.
Solar fencers
Farmers with no power source on their farms usually use a battery or solar-powered fence.
Padraic says the solar charger is a better option than just a rechargeable battery energiser because it will trickle-charge the battery. Therefore, no mains recharging will be required throughout the grazing season.
The battery will not experience deep discharges, therefore prolonging its life. This means that you do not have to be constantly recharging batteries during the grazing season.
It is essential to use a solar panel that has a power output matched to the size of the fencer. Solar panels should be south-facing to make the best use of the sunlight. The solar panel stand pictured is comprised of a solar panel and a regulator, a battery and room for a fencer.
There are two different sizes – the 10watt panel is suitable for a one-output-joule fencer (which covers 25ac) costs €190 excluding the fencer. A 20watt panel suitable for a two-output-joule fencer (which covers 40ac) costs €255, excluding the cost of the fencer. The steel frame of the unit acts as an earth system for the fencer, but Padraic advises to add an earth bar for improved earthing.
Costs of fencers
Padraic advises not to skimp on the fencer size. He says a larger fencer ensures there is power in reserve. This reserve of power may be needed if paddocks are split up with temporary wire.
Extra power is also useful for preventing green vegetation from enveloping the fence. Padraic says if there is a problem with vegetation on the fence line a larger-output fencer will not solve the problem. He says if the vegetation is removed first, the larger output fencer should burn away the regrowth, however.
In terms of cost, Padraic says fencers suitable for covering 50ac cost approximately €200 including VAT. Fencers suitable for 100 acres cost approximately €300 including VAT.
Fencers suitable for 200 acres cost approximately €520 including VAT and fencers suitable for 300 acres cost approximately €895 including VAT.
Fence maintenance
As mentioned earlier, all electric current on the fence line wants to get back to source. Therefore fence maintenance is essential to ensure the chance of leaks is minimised. Farmers should check their fence line regularly to make sure there are no signs of leakage. Here is a useful checklist to ensure a fence is working to its potential: