In what scenario can PV system DC circuits share an equipment wiring enclosure with other non-PV systems?

The correct choice is that PV system DC circuits can share an equipment wiring enclosure with other non-PV systems if they are separated by a barrier or partition. This is significant in the context of safety and code compliance within electrical installations.

A barrier or partition ensures that there is a physical separation between the different types of circuits, which is crucial for preventing electrical interference and ensuring safety. This physical division helps to mitigate risks associated with potential faults, exposes each system to its own grounding and bonding requirements, and helps to comply with installation standards outlined in the National Electrical Code.

In contrast, while having circuits not connected (the first option) might seem safe, it does not address potential issues that may arise in shared enclosures, such as electromagnetic interference. The option about being contained within a raceway focuses on containment but does not necessarily provide the same level of protection as a barrier. The last option regarding compatibility raises concerns about the specific suitability of equipment, which does not inherently ensure safety or compliance with NEC rules about sharing enclosures. Therefore, the requirement for a barrier or partition is a critical factor in ensuring both safety and compliance within the framework of NEC standards.