Three types of Furse earth rods are available. The RB205-FU copperbonded steel cored rod is the most popular due to its strength, corrosion resistance and comparatively low cost.
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 corrosion resistance at the expense of lower strength and higher cost.
Copperbond rod
Furse copperbond earth rods probably offer the installer the best and most economical.
Furse rods are made by molecularly bonding 99.9% pure electrolytic copper to a low-carbon steel core. They are not of the sheathed type. They are highly resistant to corrosion, and because the steel used has a very high tensile strength, they can be driven by power hammers to great depths.
The counter-bored couplings are made from high copper content alloy; commercial brass is not used.
Solid copper rod
Furse solid copper earth rods offer greater resistance to corrosion. They are ideally used in applications with very aggressive soil conditions, such as soils with high salt content.
Stainless steel rod
Stainless steel rods are used to overcome many problems caused by galvanic corrosion, which can occur between dissimilar metals buried nearby. Furse stainless steel earth rods are highly resistant to corrosion.
Thread and shank diameters
Confusion often arises between thread and shank diameters for threaded rods.
The thread rolling process, used by quality rod manufacturers, raises the surface of the rod so that thread diameter (B) is greater than shank diameter (A) (see drawing). All threads are Unified National Coarse (UNC-2A).
Diameter of rod
One common misconception is that the diameter of the rod has a drastic effect on lowering earth resistance. This is not true! Doubling the diameter of the rod only reduces the resistance value by 9.5% (which means increasing the weight and cost of the rod by approximately 400%).
Thus, the rationale is: Use the most economical rod that soil conditions will allow you to drive. This is one way to ensure you don’t waste money on over-dimensioned rods.
Part no. | ABB order code | Nominal diameter (”) | Length (mm) | Shank ‘A’ (mm) | Thread ‘B’ UNC (”) | Weight each (kg) |
RB105 | 7TCA083120R0014 | ؽ | 1,200 | 12.7 | 9⁄16 | 1.18 |
RB110 | 7TCA083120R0016 | ؽ | 1,500 | 12.7 | 9⁄16 | 1.55 |
RB115 | 7TCA083120R0017 | ؽ | 1,800 | 12.7 | 9⁄16 | 1.76 |
RB125 | 7TCA083120R0019 | ؽ | 2,400 | 12.7 | 9⁄16 | 2.36 |
RB205-FU | 7TCA083120R0024 | Ø⅝ | 1,200 | 14.2 | ⅝ | 1.53 |
RB210 | 7TCA083120R0028 | Ø⅝ | 1,500 | 14.2 | ⅝ | 1.88 |
RB215 | 7TCA083120R0034 | Ø⅝ | 1,800 | 14.2 | ⅝ | 2.29 |
RB220-FU | 7TCA083120R0040 | Ø⅝ | 2,100 | 14.2 | ⅝ | 2.51 |
RB225 | 7TCA083120R0043 | Ø⅝ | 2,400 | 14.2 | ⅝ | 3.00 |
RB235 | 7TCA083120R0047 | Ø⅝ | 3,000 | 14.2 | ⅝ | 3.79 |
RB305 | 7TCA083120R0049 | ؾ | 1,200 | 17.2 | ¾ | 2.19 |
RB310 | 7TCA083120R0054 | ؾ | 1,500 | 17.2 | ¾ | 2.73 |
RB315 | 7TCA083120R0058 | ؾ | 1,800 | 17.2 | ¾ | 3.27 |
RB320-FU | 7TCA083120R0063 | ؾ | 2,100 | 17.2 | ¾ | 3.83 |
RB325 | 7TCA083120R0066 | ؾ | 2,400 | 17.2 | ¾ | 4.35 |
RB335 | 7TCA083120R0069 | ؾ | 3,000 | 17.2 | ¾ | 5.44 |
UL Listed copperbond earth rod | ||||||
RB225-UL | 7TCA083120R0087 | Ø⅝ | 2,440 | 14.2 | ⅝ | 3.00 |
RB235-UL | 7TCA083120R0092 | Ø⅝ | 3,048 | 14.2 | ⅝ | 3.79 |
RB325-UL | 7TCA083120R0088 | ؾ | 2,440 | 17.2 | ¾ | 4.35 |
RB335-UL | 7TCA083120R0089 | ؾ | 3,048 | 17.2 | ¾ | 5.44 |