Many customers are very confused when they see a particular energiser given a rating quoting so many miles of fencing that may be energised by that model – often in excess of what may be required. Essentially it is meaningless, only a rough guide at best. 

  • This “Maximum Length” is a theoretical figure calculated in a laboratory situation so that if your fence was in perfect order and the best conductors have been used (0.05 Ohms/m) this sort of output may be achieved. It makes no allowance for the type of conductor, temperature, locality, time of day or possible weed challenge.  Regrettably many manufacturers do substantially over-state the capacity of their energisers.
  • Conductivity of the wire has a large effect on the capacity of an energiser. For example:- An energizer capable of energizing 9 km with a 0.05 Ohms/m. conductor will be reduced to just 1.3 km if you use a conductor of over 10 Ohms/m. Conversely, the above energizer will use far less energy in a fence of 1.3 km when a conductor of 0.05 Ohms/m is used than the same fence using a conductor of 10 Ohms/m. With conductors, the lower the quoted figure - the better it is.
  • As the temperature in the wire goes up 1°C so the resistance increases by 0.04%. This temperature is affected by the time of day, your locality and the season of the year. Not a lot but should be considered.
  • Weed challenge is a significant consideration. Energy from a fence may be drawn off the fence by living tissue. One leaf is not going to make any difference but the greater the challenge then more of the current is drawn off the fence until it may be rendered useless. It is difficult to quantify how much energy is drawn off by a particular vegetation so it is important to consider what sort of challenge you will allow before removing that challenge. The image below will indicate what will probably happen when too much grass is allowed to grow up into an electric netting situation.
  • How many lines will you including on the fence? All recommendations refer to a fence with just a single wire. If you add 2 lines then the length must be halved, 3 wires by a third, 4 lines by 4 and so on. An energiser that will do 10000 meters will only do 1000 meters of a 10 line fence.

What do we Suggest.

It is advisable you use a figure about 60% of that stated by the manufacturer. It is always advisable to buy the strongest affordable energiser as it will assist maintenance and fence security. A wimp energiser will result in a wimpy fence. Fortunately the price of an energiser does not increase relative to the energy available - Twice the energy is NOT twice the price. 

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1 comment

  • Could you provide the formula for calculating the effect of ohms on claimed distance please? I need to run around 4-5km of tape so I assume ohm/m will be an important factor to consider! Many thanks!

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