You may have heard of electric fences being used to keep animals in or out. If you’re not too familiar with the idea of an electric fence, it may seem simple to just assume that a single wire running along your boundary is enough.
If you’ve ever been at a show and seen one person poking another on the other side of the barrier; we bet you thought it was fun. But in reality, those people are getting poked because they didn’t make a complete loop!
So what should be done instead?
What Is A Circuit in Engineering terms?
In simple terms, a circuit is a closed-loop. In the electrical talk, we say that there needs to be zero voltage at any point from the source.
And for an electric fence, this means you need to have two wires running along your boundary and they have to make a complete loop back to the energizer (often called a power pack, battery or charger).
How Does An Electrical Current Work?
An electrical current is a flow of free electrons. How do they flow? Well, when you touch one end of an exposed wire, it causes the electrons to move away from that end and towards the other.
And so what happens is you get this ‘natural’ movement of electrons, which is why we refer to electricity as being natural.
But for this flow to occur, it needs two things: a source of electrons and something for the electrons to move through.
So for your electric fence, you have an energizer which gives out free electrons. As they flow towards one end, your livestock gives back their free electrons via their body chemistry as they touch the other. And this makes for a closed circuit, with zero voltage at any point along the boundary wire.
Conduction Of The Current
When the electrons travel along the wire, they bump into things. And so over time, every time a molecule is bumped by an electron it creates a little bit of heat energy. This is why you often hear ‘heat builds up in cables’.
But that’s not a problem for electric fencing because we want them to get hot!
What we don’t want is for the wire to get so cold that it stops conducting the current.
Grounding The Fence
If it’s an alternating current, then the voltage is constantly changing direction. But when you touch your fence wire, you’re in reality just completing the circuit for that particular moment in time. And so if you were to touch both ends at once, it would be like running a jumper cable from your car battery backward and touching both ends at the same time.
What Are The Components Of An Electrical Circuit For A Fence?
The way it works is that when you activate the energizer, a current will flow through the wire. But just like how your radio has to have a power source and speakers, an electric fence needs these three things:
– A power source in the form of an energizer
– Conductive wire which will carry the current
– A grounding system to stop the voltage from reaching humans or animals as they touch the fence.
Does an Electric Fence Have to Make a Complete Loop?
Yes, it does!
And as we mentioned earlier, the two wires need to make a complete closed-loop so that you have zero voltage at any point along your boundary. The energizer gives out free electrons and then they flow through your livestock via their body chemistry (their skin is acting as a battery!).
If you just had one wire, then the voltage would only exist along that one wire. And this is why we always recommend two wires – just in case somebody or something breaks through your outer boundary wire; you have a second power line to keep any stray animals or humans from accidentally touching the fence and getting shocked.
Does More Wire Equal A Stronger Fence?
No, although the more wire you have the longer your fence will be. The strength comes from how thick that wire is. So if you are looking to make a strong electric fence then it needs to be made with thicker gauge (thicker) wire than something like a garden fence which only needs thin wire.
What Happens When An Animal Or A Human Touches The Fence?
The fence will deliver an electric shock to the animal or human which can range from a powerful enough jolt that they feel pain and jump back, to one where they get knocked off their feet so you hear them yell. The more wire, the greater the distance over which it can deliver this shock. But if we go back to how voltage is voltage and current is current…
Will Your Electric Fence Hurt Birds Or Squirrels?
The more wire, the more power it will deliver to an animal or human that touches it. And so you need to think about what wildlife is in your area and how much of a shock they would feel from touching the fence.
If you have a lot of squirrels in your area, then just getting them off your fruit trees may also keep them off your electric fence. If you have chickens in a small area, then just a mild shock will be enough to stop them from getting near the wire rather than zapping them!
Electric Fence Regulations
Every nation around the world seems to have different regulations. In most countries, including America, you need a minimum of two wires on your electric fence and it must be at least 50cm from the ground. But in Australia, their regulations are not quite as strict where single-wire fences can meet their standards!
But this is probably because there are a lot of large and very venomous snakes in Australia. So if they think your fence is strong enough to keep people away from their electric fence (as well as these deadly animals) then it will pass the regulations!
What Is The Ideal Voltage For An Electric Fence?
The minimum voltage for an effective electric fence is usually considered 3000 volts. But this value can be difficult to understand because you don’t want all your electricity just going into the wire. This is why it is a good idea to look for chargers with a higher voltage rating so that they deliver more current through and along the fence line.
You need to make sure that the distance between each wire is no more than 18 inches (45cm). This is because if you have a gap between wires, then it reduces the voltage gradient and thus the strength of your electric fence.
The last thing you want is for an animal to be able to get its leg through two or three rows of wires and end up touching two or three at the same time!
Electric Fences In Populated Areas
If you live in an area that is heavily populated with people and livestock then you need to make sure that your fence is a minimum of 10,000 volts. If there are any gaps between wires or if the charge dissipates quickly, then this can cause your animals to escape – even if they’ve only gone through it once before!
Another thing you need to think about is that in populated areas, there will be a lot of wires around already. These might be underground and thus not easy to spot but they can interfere with your electric fence. To avoid this, you need either:
1) A lot more wire
2) To make sure neither of the fences is close together (at least 3 meters apart)
The reason for this is that power needs to be transferred along the wire rather than just being created when an animal touches both wires at once.
Mistakes To Avoid With Electric Fencing
There are a few things you should avoid when using an electric fence.
One of the most common mistakes people make is to put up their fence and leave it for a few days, only to come back and find an animal has been injured by touching two wires at once!
The solution is simple: always test your new fence on yourself first!
You should also not touch the fence yourself or you will get a big shock. It’s always a good idea to have someone else do it for you so they can shout out if anything goes wrong.
This is just common sense but there are other mistakes to avoid when using an electric fence too:
1) Charging your system for too long
It is best to let your charger run for between 8 and 12 hours at a time.
2) Having too many chargers for the amount of wire you have
This means that none of your wires are getting a strong enough charge to keep the animals off.
3) Using too small a wire size for high powered chargers
4) Using fuses or circuit breakers that are too small for the amount of electricity your fence puts out.
5) Charging your fence at night
Nighttime is when animals are most active so it’s a good idea to charge your fence during the day (unless you know that there aren’t any large predators around, of course).
6) Charging the whole length of your fence at once
It’s a good idea to do individual sections for 5 or 10 minutes at a time. This means that any animals in the area won’t be tempted to stay near an electrified fence for too long.
Will an electric fence kill you?
Almost certainly not. There are stories of people who have been dragged by cattle over an electric fence but even this isn’t certain. Also, there is a much higher chance of you being killed by lightning than from an electric shock through a wire.
Does a complete loop make your fence stronger?
No, it’s best to just have a single strand of wire going right around your boundary. If you have two wires, one on the inside and one on the outside then this is called a split fence. Animals can learn from touching both wires that an electric current comes through them – so they stay away!
How far apart should electric fence wires be?
This depends on the voltage of your electricity and how much you want to spend on the wire. Generally, you should make sure that your wires are about 8 inches apart.
What happens if you don’t ground an electric fence?
If you don’t ground an electric fence, then there will be a lot of resistance in the system. This means that your charger or battery will go flat very quickly and it might even damage them over time.