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Electric fence

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Just getting around to acquire an energiser and a bit puzzled by the spec. Typically it says a it's good for a single wire of 8km or multi-strand (that is, two) of 3km. I would have thought that a typical fence with two runs would have them in parallel rather than series, so the length would be 8km for one or two runs.

What am I missing? Is it normal to have the strands in series? Seems a bit daft to me! Or is there something else in play?

Here is the actual spec, which doesn't match what you wrote:

--- Quote ---Fence Length two-wire 7 km
Fence Length two-wire - Light vegetation 3 km
Fence length multi-wire - Recommended max 0.5 km
--- End quote ---

From what I see
- Two wire means a ground and hot wire
- Multi-wire could be 3 or more hot/ground pairs, supplied in parallel. So I don't know how the 0.5km number is calculated.

Yeah, depends how you read it. The features bit says 7km (must've been thinking of output when I wrote 8) which I assumed would be single wire. Lower down it says two wire, but then a bit lower it is 'multi-wire' at 0.5km.

I just happened to pick this one as the one I was looking at, but they all seem to have a similar reduction in length for multi-strands. A more upmarket one, the Gallaher M550 says 110 (presumed km) for single wire, 35 for two wire and 9 for multi-wire.

The M550 maybe makes a bit more sense, 25km rating with one pair, divide that by 3 pairs gives 8.3km which is close to the 9km multi-pair rating. Assuming its 3 pairs because they write (3) for multipair.

There are probably so many factors they just give these ballpark numbers. If you care you can probably go and measure the voltage upon install.

--- Quote ---In the past most manufacturers included some form of rating in kilometers or miles of fence. Many still do. In the past they tended to use a simple formulae rather than any form of testing on actual fences. Also, some did not say how low the fence voltage would be at the end of this amount of fence. So these figures were at best theoretical. More recently these numbers are being qualified and in some cases related to the load on the fence or the animals to be fenced. In practice it is also factors like the fence layout, materials and even soil type that determine the number of kilometers that can be energised. A kilometer rating is useful however, because it can most easily be related back to the buyer's property. It should be understood, however, that the figure relates to a "best case" fence, unless it is qualified as to the type of fence and worst point kilovolts used to get the figure.
--- End quote ---

There seems to be a dependence on vegetation, but as in many devices they aren't consistent on conditions and definition.


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