Electric Fencing

 Knowledge Nuggets | Fact Sheets

Knowledge Nuggets

  • The effectiveness of any electric fence depends on the ability of the fence to deliver an unpleasant shock to animals that touch it. The ability of a fence to deliver that shock depends on the energizer, it’s grounding and the fence design.
  • An energizer (also called a charger or controller) regulates the flow of electricity in an electric fence. It stores electrons in a "capacitor" and then releases them in a "pulse." After each pulse the capacitor stores up electrons for the next pulse.
  • We can measure the voltage in an electric fence with a special peak reading voltmeter. The voltage rating of an energizer tells you whether an animal will get a shock or not. The higher the voltage the further a shock will jump. Long-haired animals need higher voltage to get a shock than short haired animals.
  • The "joule" rating measures the total amount of energy released per pulse and describes how big the shock is. Joules = volts x Amps x pulse time. A small energizer powered by “D cell” batteries can deliver approx. 0.1 joules with 7500 volts. Energizers that run on 120 Volt power, may be rated at 1.3 up to 40 joules with 6000- 8000 volts.
  • Energizers differ in the size and duration of the pulses of electrons they send into the fence line. A good energizer has an intense pulse lasting for 0.0003 seconds. These short pulses eliminate the risk of fire (the pulse is so short that no heat builds up in the wire). Poorer quality energizers have pulse lengths of 0.003 to 0.3 seconds. This longer "on" time may allow sparks to arc and heat to build up. This will also shorten the life of polywire.
  • Generally speaking, high voltage energizers with long pulses are high impedance energizers. Low impedance energizers resist electrical leakage to the ground through weeds, grass or poor insulators. Low impedance enables the energizer to make the utmost use of its available energy into a heavy load.
  • Buy an energizer with the capacity to do the job. Secondly, compare the value of energizers by calculating the cost per joule. Generally speaking, the lower the cost per joule the better the value.
  • Poor grounding is the leading cause of electric fence problems. For an animal to receive a shock it must complete a circuit. The circuit can be either from the energizer through a "live" wire through the animal, through the soil, and through ground rods back to the energizer, or from the energizer, through a live wire, through the animal, through a ground wire back to the energizer.
  • A minimum of three ground rods should be used for each energizer. Half inch diameter galvanized steel rods or 3/4" galvanized pipe make the best ground rods. They should be at least 6 feet long, driven 5-1/2 feet into the soil and be spaced at least ten feet apart. More ground rods may be needed in dry areas. If your fence includes ground wires, it is advisable to install additional ground rods connected to the ground wire at 1500-3000 foot intervals along the fence line depending on general soil moisture levels.
  • Troubleshooting is easier with a good voltmeter. A voltmeter enables you to isolate problems by determining if your energizer is charging the fence, if the grounding is adequate and if power is reaching the end of the fence. Digital and dial type voltmeters that can register up to at least 5000 volts and are accurate to +/- 100 volts are ideal.
  • Some testers are available that show only if a fence is "hot" or "dead." However, it is also important to know how much power is available in the fence. If power drops below about 4000 volts, the fence will not be very effective against wildlife. Sheep require a minimum of 3500 volts and cattle and horses require a minimum of 3000 volts.
  • Fixing electric fences is a process of elimination. Begin the inspection with the energizer and grounding system. Then check the wires connecting the energizer to the hot wires on the fence. Then follow the hot wires to the end of the fence. With the use of switches in your fencing system, you can locate leaks by separating parts of the system and measuring for drops in voltage. By isolation it is possible to locate leaks.
  • Walking the fence line with a battery powered transistor radio can help locate cracking or arcing insulators. Turn the radio between stations. If the insulators are insulating, there won't be any sound. When the radio gets near a broken or leaking insulator, you'll hear clicking on the radio. As you get closer to the faulty insulator, the clicking will get louder.
Fact Sheets

Dry Periods Mean Extra Attention to Electric Fencing

Electric Fence Controllers

Electric Fence Energizers - available in PDF format only

Energizers and Energy - available in PDF format only

Farm Fencing Systems

Fence Systems for Grazing Management: 1. Electric Fence Energizers - available in PDF format only

Fences That Work: Temporary Electric Fence Materials Evaluation - available in PDF format only

Grounding Electric Fences - available in PDF format only

Grounding Systems for Electric Fences - only available in PDF format

Temporary Fencing For Rotational Grazing - only available in PDF format

Trouble Shooting Problems with Electric Fences - available in PDF format only

9 Winter Electric Fencing Tips
  For more information about the content of this document, contact Grant Lastiwka.
This information published to the web on September 3, 2003.
Last Reviewed/Revised on March 2, 2017.

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