For PV systems that are standalone units, the DC system grounding electrode conductor must be as large as the largest output conductor supplied by the PV system, or at least which size, whichever is larger?

• A. 8 AWG
• B. 6 AWG
• C. 4 AWG
• D. 10 AWG

Answer: (A)

In a standalone PV system, the DC grounding electrode conductor (GEC) must provide a low-impedance path back to the grounding electrode in case of a fault. The code sets a practical minimum size for this conductor: it cannot be smaller than 8 AWG copper. At the same time, the GEC must be sized to be at least as large as the largest DC output conductor in the PV system. So you use the larger of those two: the largest DC output conductor or 8 AWG, whichever is bigger. That’s why 8 AWG is the minimum you’d ever use, and if the system uses larger DC conductors (for example, 6 AWG), you would size the GEC to that larger size.