Shocking facts about electrical fences

I ran across a basic misconception about how electric fences work on some other blog, and I think it's worth talking about the electric fences I use here, and how they're set up.  

The misconception was that "more wires means higher resistance", and the discussion was how a fence with many conductors (8 or 10) was somehow producing a higher resistance than a fence with 3 conductors.  

Voltage decreases with the length of the wire, and with the diameter of the wire.  You get the least amount of voltage drop with a larger wire, or a shorter length, or both.  

Voltage is what keeps your animals off the fence:  The higher the voltage, the more effective the shock, and (unsurprisingly) the more careful the animal is to avoid the fence.  if any of you have been shocked by a properly working 50 mile charger, you know what I mean.  I take special pains to never, ever repeat that experience!

So if you have a very long run for your fence charger, you'll be better off using the thickest wire that you can find.  Now I'm not talking about the ROPE or TAPE diameter.  Most electrical fences that aren't metal use some sort of non-conductive or marginally conductive plastic rope or tape, with stainless steel threads woven through it.  The voltage is conducted through the metal part of the fence, the stainless threads.  The size of the rope, or tape, is not important.  

That's an important distinction.  When you are looking at one kind of electric fence vs another, you want to pick the one that has the most METAL, not the biggest rope.  So  count the threads and pick the highest count.  If you are running very long distances, consider using a bare wire of the largest diameter (gauge) that you can find.  That's usually something like 12.5 gauge, but if you can find thicker, buy that for longer runs.  

The "size" of the "wire" (or I'll use "pipe" ) is the total diameter of all of the threads.  The more threads, the wider the pipe,the less resistance to voltage.   You can get this same effect, and I do, by stringing multiple conductors.  each conductor "widens" the pipe, lowers the resistance, and gives you better voltage at distance.    

How do you tell if the wire is thick enough?  Test the voltage at a distance.  You want to see at least 4,000 volts everywhere as a minimum.  With my fencing I see 18k volts at the fence charger and between 9 and 11,000 volts at various points in the field.    If my voltage drops, that's my sign that I need to go clear the fenceline.  If it never gets that high it means I should probably string another conductor or two to increase the size of the pipe delivering the voltage.  

Your voltage will decrease every time that your wire touches something; in the case of the blog I was reading, the problem that the author had wasn't that there was too many wires, it was that with the larger number of wires more of them were touching the ground and weeds.  More touching, less voltage.  When she reduced the number of wires to 3, her voltage went up because her fence grounded out less, not because fewer wires were less resistance.  

People use round rope electric fences -- I do -- or they'll use a tape, and the primary reason that they use the tape is that it's more visible to animals that might otherwise ignore it.  I use the rope because the pigs I am mostly containing hate electric fences, and will look carefully for them when they're out walking, and the rope is easier for me to coil and store.  I'm used to handling big shots of rope.