Q: Can you explain where lightning arrestors are needed?

A: There are a few sources of electric surges in electric wiring, the most damaging to most inverters being from the AC side. The most common source is from the utility. This can be from the long distribution lines that can pickup surges from lightning or from loads elsewhere that send a surge onto the lines. Other sources are from a poorly controlled engine generator, or long lines to AC loads particularly well pumps. Surges from PV arrays can be from nearby lightning strikes that induce a surge in the wiring in or from the array. Longer wiring runs are more susceptible than short wire runs. Generally this surge will damage the inverter or charge control and the lightning arrestor will be more effective at the end of the circuit near the equipment to be protected. A second lightning arrestor at the array will give additional protection.