PV system dc circuits utilizing metal-clad cables installed in metal raceways can be exempt from AFCI protection when installed in what conditions?

In the context of the National Electrical Code (NEC) Article 690, photovoltaic (PV) systems that employ direct current (DC) circuits using metal-clad cables within metal raceways can indeed be exempt from arc-fault circuit interrupter (AFCI) protection under specific conditions. The correct condition is when these installations are not located in or on buildings.

The reasoning behind this exemption lies in the nature of the environments where the equipment is installed. When metal-clad cables are installed in metal raceways outside of buildings, the risk of arc faults can be significantly reduced compared to indoor installations. This is primarily due to factors such as environmental exposure and the possibility of physical damage, which is typically less likely outside when proper installation methods are used.

Other choices such as installations exclusively on rooftops, inside buildings, or underground don’t address the specific condition that would allow an exemption from AFCI protection. Hence, the requirement is oriented toward the environment where the PV systems are installed rather than the specific location within certain structural confines. This ensures a balanced approach to safety while allowing advancements in solar technology installations without undue burdensome regulations.