NEC Article 690 governs photovoltaic systems, and it’s updated with every code cycle. Before you start any solar install, read the article relevant to your jurisdiction’s adopted code cycle.
Rapid Shutdown (690.12): all rooftop residential solar installations must have a rapid shutdown system that brings the conductors on the roof to under 30V within 30 seconds of initiating shutdown. SunSpec-compliant module-level power electronics (microinverters like Enphase, or DC optimizers like SolarEdge) satisfy this requirement. String inverters need a separate rapid shutdown switch and transmitter.
DC wiring considerations: PV source circuits can be in conduit or not depending on the cable type (USE-2 or PV Wire can run exposed on the roof rack, THWN requires conduit). In a string system, all panels in series must be wired with consistent polarity. A reversed panel cuts the string output significantly. Label everything - DC wiring must be labeled with red for positive, white with red stripe for negative. Labeling requirements are extensive and inspectors will fail you for missing labels even when the wiring is perfect.