When an animal on the fence does not feel the expected jolt, owners of electric fencing systems usually suspect the device or the wire first. In practice, the most common culprit is grounding: an estimated more than 80% of installed grounding systems are inadequate. Below we explain why grounding matters so much and how to design it correctly.
Why grounding is part of the same circuit
An electric fence is a loop system through which electricity flows in a closed circuit. The current that flows through the wire, the animal and the grass into the ground has to return to the device via the ground rods. Soil is a relatively poor conductor of electricity, especially when it is dry, sandy or rocky. That is why it is important to size the grounding correctly, since only then can the device develop its full power along the entire length of the fence.
A typical grounding for a grazing system consists of probes (ground rods) connected to the device, which in turn is connected to the fence via a wire. If any link in this chain fails to do its job, the whole system weakens, even if the device and the fence wire are perfectly fine on their own.
Five rules for reliable grounding
- Choose the right number of ground rods for the power of your device; recommendations are usually given separately for each unit.
- With low-conductivity soil combined with a powerful device, you may need more rods than the basic recommendation.
- Make sure every connection in the grounding system is screwed tight; a poor connection acts as a bottleneck for current.
- Every part of the grounding system should be hot-dip galvanized or made of stainless steel, since rust acts as an insulator and hinders conductivity.
- Check the grounding system regularly, both right after installation and during operation, especially during dry periods when soil conductivity drops.
What determines how many rods you need
Besides soil type, the main factor determining how many ground rods you need is the power of the energizer. A more powerful device releases more energy into the fence, so the path the current takes back to the device also has to be sized accordingly, otherwise part of the power is lost before it reaches the end of the fence. Recommendations for the number of rods per specific model can be found in the technical tables for each energizer, so it makes sense to follow them per device rather than applying one single rule to every unit.
Besides grounding, wire choice also affects conductivity. Long fences require highly conductive wires: for wires with resistance up to 2.4 Ohm/m we recommend a fence length of up to 400 m, for resistance up to 0.32 Ohm/m up to 3000 m, and for resistance up to 0.13 Ohm/m up to 8000 m. The difference between well- and poorly-conducting wire is very noticeable on long fences: with 8000 V at the start of the fence, a well-conducting wire can still hold around 7500 V after 1000 meters, while a poorly-conducting wire can drop to as little as about 800 V. Grounding and wire conductivity therefore work hand in hand; even the best wire will not help if the current cannot return to the device.
A similar drop with distance can be seen with electric netting: if the voltage at the start of the fence is 8000 V, a well-designed net keeps around 7600 V at 100 meters, about 5300 V at 1 km, and still around 3100 V at 3 km, while a less conductive net drops to just 6000 V, 2000 V and only 800 V at the same distances. Something similar applies to wires: with thick 2.5 mm steel wire, in practice lengths of up to 120 km are achievable for a four-wire fence without undergrowth, while for a single-wire fence with the same wire that maximum drops to 30 km. If you use a thinner stainless steel strand (6 x 0.20 mm), the sensible maximum fence length shrinks to around 250 m, and even more if the fence is overgrown. All these figures point to the same conclusion: good grounding has to be combined with sufficiently conductive wire, or the device's power gets lost before it reaches the end of the fence.
How to recognize grounding as the cause
If a fence performs weakly despite a fully functional device and well-conducting wire, it makes sense to check the grounding first, especially during dry periods when soil is a poorer conductor. Check whether all connections are screwed tight, whether the rods are made of a suitable, rust-free material, and whether there are enough of them for the device's power. Because soil conductivity changes throughout the season, a single check at installation is not enough; it is worth inspecting the grounding system at least once a year.
As PATURA's Slovenian partner, Kancler Sistem Pro always pays particular attention to grounding when setting up grazing systems, since it is the part of the system most often overlooked, yet crucial.
Need advice?
If animals still do not feel a proper jolt even with a new energizer, take a look at the earth rods and accessories in our electric fencing range.