In addition to conductors, earth rods and plates or any combination thereof can be used to achieve an effective earth depending on the site conditions.
Earth rods take advantage of lower resistivity soils at greater depths than normal excavation will allow, whilst earth plates are used to attain an effective earth in shallow soils with underlying rocks. Earth plates can also be used in locations with large amounts of buried services, as well as provide protection in potentially dangerous places e.g. HV switching positions.
Quality earth rods are commonly made from either copperbonded steel, solid copper or stainless steel. Solid copper and stainless steel rods offer a very high level of corrosion resistance at the expense of lower strength and higher cost.
Three types of Furse earth rod are available, but the copperbonded steel cored rod is by far the most popular, due to its combination of strength, corrosion resistance and comparatively low cost.
One common misconception is that the diameter of the rod has a drastic effect on lowering earth
resistance. This is not true! You only lower the resistance value by 9.5% by doubling the diameter of the rod (which means increasing the weight and the cost of the rod by approximately 400%).
That's why we advise you use the most economical rod that soil conditions will allow you to drive. This is one of the ways to ensure that you achieve successful earthing, but also don’t waste money on over-dimensioned rods.