September 1999

Equipotential planes are now required by the 1999 National Electric Code (Section 547-9) to be imbedded in the concrete floors of all livestock confinement areas that have electrical service. They have been recommended for many years as a method of preventing stray voltage from affecting livestock. A metal grid is installed in the concrete floor and is connected to the metal stalls and the equipment the livestock can touch. The grid is bonded back to the building grounding system. If the stalls and floor are connected together, a voltage cannot develop between them.

An equipotential plane is easy to install when constructing a building. Before pouring the concrete floor, reinforcement steel mesh can be welded to stall dividers and to metal equipment. It may be easiest to braze a copper wire to the steel mesh. The wire must be size AWG No. 8 or larger where the wire comes out of the concrete; sleeve it with a short piece of plastic conduit to keep it from breaking off.

In the unlikely event that stray voltage gets to a level the cows can feel, a voltage gradient ramp will be needed at places where livestock enter orleave the equipotential plane on a daily basis. A common method to build a ramp is to drive ground rods into the earth at a 45 angle at each entrance (four rods are usually enough). A copper wire can be used to connect the ground rods to the equipotential plane. More installation information can be found in ASAE Engineering Practice EP473, Equipotential Planes in Animal Confinement Areas.

Robert Fick

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