Quick Answer
People often make mistakes with grounding solar systems by not using sufficient grounding rods, ignoring bonding requirements, and not properly sizing the grounding system for the solar array.
Inadequate Grounding Rods
Using a single grounding rod is not sufficient for a solar system. It is recommended to use at least two 8-foot long copper-clad grounding rods spaced at least 6 feet apart, and driven to a depth of 8 feet in the earth. A more common and recommended installation uses 2-3 rods at 8-foot intervals. This ensures a lower resistance path to ground and provides a safe path for fault currents to flow.
Bonding Requirements
Bonding is a critical component of a solar grounding system. All metal components, including the array frame, inverters, and grounding rods, must be bonded together to prevent voltage differences between them. This is typically achieved by using 6 AWG or larger copper bonding cables. A good practice is to bond the array frame to the grounding rods with a 2-foot length of 6 AWG copper cable.
Sizing the Grounding System
Sizing the grounding system correctly is essential to ensure it can handle fault currents. The size of the grounding system is typically determined by the current-carrying capacity of the array and the inverter. A common rule of thumb is to size the grounding system to carry at least 1.5 to 2 times the maximum expected fault current. For example, if the inverter is rated for 100A, the grounding system should be sized to carry at least 150 to 200A.
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