So I got a customer that has an electric fence for his horses, the instructions call for three ground rods on the negative side of the transformer 10 feet apart. The transformer is mounted on the outside of the barn, the barn is 500 feet away from the home. The barn has a 100a sub panel with two ground rods, is it possible to bond to the existing rods for the barn?? If not "other than the manufacturing specs" why not? Will driving three more ground rods create an impedance between the existing rods?