Don't turn a horse out into a large area until he knows about the electric fence. Even then, if it's a large paddock or pasture he's not familiar with, lead or ride him around the fence boundary before turning him loose.
A Note on Safety
A wire that doesn't break can cause serious injury. Most webbing or tape will break if a horse hits it hard enough. You want the tape and wire within it to be the same strength. A wire that's stronger than the tape around it can injure the horse if the tape breaks and the wire doesn't.
Sunlight weakens plastic and vinyl polymer tapes or ropes, and they may disintegrate after a year or two. Use the ones with UV inhibitors and try to purchase only the ones that have a 20-year guarantee.
Sunlight also damages plastic insulators. Some experienced ranchers report that the black ones seem to stand up to the elements better than the light-colored ones.
Traditional electric wire has low visibility unless flagged with bright pieces of cloth, surveyor tape, or some other material. The newer fence tapes, ropes or web strips are more easily seen. Lightweight white or orange nylon tapes (with wire filaments woven into them to carry electric current) flutter in the breeze and are highly visible. The white ones are most visible from a distance unless the ground is covered with snow. The 1.5-inch stiff electric tapes (such as HorseGuard) combine good visibility with greater longevity.
Check the fence often to make sure it's working. Wet vegetation can cause a short. Wild animals may push the wire or tape into the solid fence next to it, or stretch and break the hot wires. If the wire/tape gets caught on nails, metal fence, or any other metal object, it will likely cause a short.
Periodically trim grass and branches away from the fence in summer when plants are growing rapidly. If your bottom wire is hooked up separately from the others, you can unhook it when grass is tall. That way the grass won't short out the whole fence.
Most fence chargers have a blinking light to indicate the fence is working. The light will go off if it's not plugged in or if there's a short. You can also use a fence tester to check for any charge in the wires. The tester uses a small grounding rod and a wire to touch the fence. If the fence has a current, the light in the tester will go on. The best kind of tester has several small lights and tells you how strong the current is. A weak current will light only one bulb, whereas a strong charge will light them all.
If you don't have a tester, use a long blade of green grass. If you don't feel any shock, slide the grass over the wire so your hand comes closer to it, until you feel a pulse through the grass, to know the fence is working weakly. If you feel nothing, the fence isn't working at all.
