Electric Fencing 101
What is an electric fence?
An electric fence is a psychological barrier that keeps farm animals in and wild animals and vermin out - even over long distances.
Basics of Electric Fencing:
Electric fencing is ideal for grazing or pasture management by containing animals on a selected area of pasture or crop. It also may be used to excluded livestock and wildlife from unwanted areas.
Permanent electric fencing is economical, easy to install and easy to maintain. Temporary electric fencing is an effective temporary barrier for short-term animal control and rotational grazing.
Reasons for using Electric Fencing:
- Keep domestic animals in
- Keep wild animals and vermin out
- Separate different groups of animals
- Allow rationing of crops and pasture
- Fence off eroding areas, trees, rivers and roads
- Electric fencing has revolutionized pasture management techniques and better pasture management means better profitability for farmers. Permanent or portable electric fences are used to subdivide pasture to ensure even distribution of manure over grazing areas. In this way, pastures are kept fresh, short and palatable which ultimately leads to increased milk and meat production.
Reasons for using Electric Fencing:
- Safe: Animals remember the short, sharp but safe shock and develop respect for the fence.
- Easy to install: An electric fence takes less than half the time to build compared to traditional fence systems.
- Durable: A non-electrified fence experiences constant wear and tear under stock pressure. Because your animals learn to avoid an electrified fence, your fence will last longer and remain in good condition.
- Economical: Electric fences cost less than 50% of traditional non-electric fences.
How does an Electric Fence work?
A pulsed electric current is sent along the fence wire, about one pulse per second, from an energizer which is earthed. When the animal touches the fence it completes the circuit between the fence and the ground and receives a short, sharp but safe shock. The shock is sufficiently memorable that the animal never forgets.
An electric fence is a psychological barrier so doesn’t require great strength to be effective. However, it must be well designed and constructed to absorb some pressure from animals, snow and wind. The energizer must have enough power for the length of the fence and for the animals being controlled. More power is better then not enough
Electric current (AMPS) only flows when a circuit is completed between a positive and negative terminal.
In this diagram the current cannot flow from the positive terminal to the negative terminal because the switch is open.
In this second diagram, the switch is now closed, allowing the current to flow from the positive terminal through the light bulb (lighting the bulb) to the negative terminal.
An electric fence circuit is made on a larger scale. The energizer fence terminal (positive) is connected to the insulated fence wires, and the energizer earth terminal (negative) is connected to galvanized metal stakes driven into the ground.
The same 'circuit completion' (second diagram above) is necessary before the animal gets a shock. An animal standing on the ground and touching the electrified wires (shown right) will complete the circuit like the closed switch in the second diagram above.
For example, a bird sitting on the wire will not receive a shock (shown left). It is not touching the ground so the circuit is not completed. A person wearing insulated footwear will only receive a small shock because all the current cannot pass through the insulated soles.
Dry, sandy or pumice soil is a poor conductor of electric current, so it is a good idea to add an ground (negative) wire into the fence. The animal must touch both a hot wire and ground wire to feel an effective shock.
Choosing the Right Energizer (Fence Charger)
Once you have decided what type of electric fence you want for your property, you will need an energizer also known as a fence charger to power it. The correct energizer size for your property is determined by the type of animal to be fenced, fence distance to be powered and the number of wires in the fence.
There are several types of Energizers:
- Mains powered - these are energizer units which are plugged into a 120V mains power supply.
- Multi powered - these are energizer units which can be left out in your paddock and can be powered by a 12V deep cycle battery or plugged into 120V with the supplied adapter.
- Battery only energizer - These energizers require a battery or batteries to operate
- Solar - All in one solar energizers house the energizer, batteries, and solar panel although these are the most convenient energizer it is also the most costly per joule. Note that most any multi power or battery energizer can be paired with a solar panel and charge controller to become solar powered.
Steps to Good Grounding
Grounding is perhaps the most neglected component of many fence systems. FenceFast recommends energizer main systems to have at least three ground rods, 5-7’ deep and spaced 10’ apart are the minimum recommendation. Good rule of thumb is 3ft of ground rod for every 1 joule of energizer. Never attach copper to steel. Electrolysis can occur and result in corrosion which weakens shocking power. Use only galvanized or stainless steel ground wire and grounding rods to avoid this problem as most energizers use galvanized or stainless steel terminals – not copper. Think of your ground system as an antenna that gathers electricity in order to deliver the shock to the animal. The bigger and better the antenna the better the signal is received. Having a hose clamp holding a piece of copper wire to a rusty t-post or rebar is often the weakest link of many electric fence systems and the main issue with 80% of the electric fence systems out there.
Temporary Portable Electric Fencing
A temporary Portable electric fence provide flexibility in pasture management and are ideal for short-term animal control or rotational grazing. Easily transported, constructed and maintained, portable fences are an effective temporary fencing solution for a range of animals and situations. These fences can be quickly constructed and moved as often as needed. Temporary electric fences are terrific choices for cattle and horses. They are sufficient for sheep and goats but require more work and greater attention to detail (i.e., wire spacing, available posts, line tension, etc.). Temporary electric fences are also excellent for overnight trail rides to control horses and on camping trips to keep unwanted animals away from your campsite.
Temporary electric fence utilizes an electrified wire, tape, or rope and temporary fence posts to quickly section off portions of your pasture for rotational grazing or direct livestock to a desired area. The electric shock given to the livestock does not hurt the livestock, but trains them to avoid contact with the fence. Once trained, the electric fence acts as a psychological barrier instead of a physical barrier like a standard barbwire fence. Temporary electric fences can be constructed quickly using easy to install fence posts, electric wire/rope/tape reels, and portable battery or solar powered energizers.
There is a misconception that dry vegetation touching an electric fence can cause fires – this is extremely unlikely. In order to create a short, vegetation needs to be damp or green so therefore the vegetation will not ignite. Once vegetation dries out it becomes non-conductive meaning any short created disappears.
The only conceivable but still very unlikely scenario where an electric fence could start a fire is when a wire shorts to a grounded metal object, such as a steel post or wire where insulators have broken, in the presence of abundant dry vegetation. This scenario is very unlikely to occur in practice, and even less so on a well-maintained fence. Producers with fences on steel posts or using earthed wires are advised to ensure the live wires are well insulated and the fence is clear of vegetation. If these factors are of concern then on days of severe or above fire risk, consider switching the energizer off.