| 1-1. Systems. Grounding systems are installed using grounding rods, conductors, or plates. Grounding rods must be copper, steel, or iron/steel (galvanized) pipe that is at least 8 feet long. Ground resistance must be less than 25 ohms to ground (earth). In order to get resistance below 25 ohms to ground, you may need to drive a ground rod deeper than 8 feet, install additional rods, or add chemicals to the soil. Metal water pipes can be used to supplement a grounding system. One of the most important parts of electrical installation is the grounding rod (Figure 1-1). 
Figure 1-1. Grounding rod a. The best grounding rod (electrode) is made of copper (nonferrous metal) and is at least 1/2 inch in diameter (Figure 1-2). 
Figure 1-2. Copper grounding Wire b. A copper-coated, steel grounding rod is at least 1/2 inch in diameter (Figure 1-3). 
Figure 1-3. Copper-coated, steel grounding rod c. A solid-steel (ferrous metal) grounding rod is at least 5/8 inch in diameter (Figure 1-4). 
Figure 1-4. Solid-steel grounding rod d. An iron/steel (galvanized) grounding rod is at least 3/4 inch in diameter (Figure 1-5). 
Figure 1-5. Iron/steel (galvanized) grounding rod e. For ease of storing, some grounding rods are constructed in 3-foot sections (Figure 1-6). 
Figure 1-6. Grounding-rod sections
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