When it comes to installing PV modules, compliance with electrical codes isn’t just a recommendation—it’s mandatory for safety, performance, and legal approval. Let’s break down the key requirements you’ll encounter, from the National Electrical Code (NEC) to local amendments that might impact your project.
First, NEC Article 690 serves as the backbone for solar installations. This section specifically addresses photovoltaic systems, covering everything from circuit sizing to grounding. For example, NEC 690.31(F) dictates that PV source and output circuits must use wiring methods rated for sunlight resistance if exposed outdoors. That means cables like PV Wire or USE-2 are non-negotiable in most exterior applications. Don’t even think about using standard NM-B cable here—UV degradation will wreck it within years.
Spacing requirements often trip people up. NEC 690.34 mandates maintaining a 1-inch airspace between roof surfaces and PV modules unless the module is listed for direct contact. This isn’t just about heat dissipation; it’s critical for preventing moisture entrapment that can rot roofing materials. For tilt-mounted systems, you’ll need to maintain at least 3 feet of clear access along one edge of the array for firefighter access, per International Fire Code (IFC) 605.11.3. These dimensions aren’t arbitrary—they’re calculated based on ladder truck operations and emergency egress.
Grounding gets technical fast. NEC 690.47 requires both equipment grounding conductors (EGC) and a separate grounding electrode system for arrays over 100kW. But here’s where installers often miss the mark: bonding all metallic components within the array zone. Each PV module frame must be bonded to the grounding system using listed clamps or connectors—no wrapping bare copper around frame edges. The Aluminum Association’s standards specifically prohibit direct contact between aluminum frames and copper grounding conductors without anti-corrosion measures like zinc-plated hardware.
Overcurrent protection follows strict rules under NEC 690.9. Every PV source circuit needs overcurrent devices rated for 1.56 times the module’s short-circuit current (Isc). Why the multiplier? It accounts for continuous operation under ideal irradiance conditions. For a typical 10A Isc module, you’d need a 16A fuse or breaker. But wait—module-integrated rapid shutdown adds another layer. NEC 690.12 demands controlled conductors within 1 foot of rooftop arrays de-energize to 80V or less within 30 seconds. This requires listed rapid shutdown devices compatible with your PV module’s voltage and current specs.
DC vs AC wiring rules vary significantly. While AC circuits follow standard NEC Article 310 guidelines, DC circuits require special considerations. NEC 690.8(B) specifies that PV system DC circuits must be sized at 125% of the maximum current, which includes both continuous output and any reverse current from parallel strings. For combiner boxes, each input circuit needs individual fusing if the combined parallel source circuits exceed the ampacity of the output conductor.
Roof penetration details matter more than most realize. The International Building Code (IBC) 1507.17 requires flashing kits rated for the specific roofing material—asphalt shingles need different seals than standing seam metal. Each mounting foot must maintain at least 2 inches of clearance from roof seams or edges. For tile roofs, specialized hooks that interlock with the tile profile are mandatory—drilling through actual tiles compromises waterproofing.
Labeling requirements get surprisingly specific. NEC 690.56(A) dictates that every service disconnect must be marked with: “PHOTOVOLTAIC SYSTEM AC DISCONNECT” in black letters at least 0.5 inches tall on a red background. DC combiners need “PHOTOVOLTAIC POWER SOURCE” labels visible from the front. Even conduit runs aren’t exempt—every 10 feet of exposed DC PV circuit conduit requires “PHOTOVOLTAIC POWER SOURCE” markings.
Commissioning tests aren’t optional. Before energizing, you’ll need to document: insulation resistance tests (minimum 1 megohm per NFPA 70B), ground-fault protection verification (for systems over 50kW), and I-V curve tracing to confirm string performance matches module specs. Thermal imaging of connections under load helps spot loose terminals that voltage tests might miss.
Local amendments can override NEC basics. For example, California’s 2022 Solar Rights Act requires all residential systems to include a 200A busbar rating unless the utility approves a load calculation showing adequacy. Florida’s High-Velocity Hurricane Zone (HVHZ) codes demand modules withstand 175 mph winds—that’s 40% stronger than standard UL 1703 testing. Always check municipal amendments before finalizing designs.
Maintenance requirements embedded in codes often get overlooked. NEC 110.12 requires annual torque checks on all field-terminated connections—vibration and thermal cycling can loosen even properly installed lugs. NFPA 70E mandates arc flash labeling on all DC combiner boxes, with incident energy calculations based on maximum fault current from parallel strings.
The takeaway? PV installation codes layer multiple requirements that interact in non-obvious ways. A module that’s UL 6703-certified for grounding might still need supplemental bonding in certain jurisdictions. A racking system that meets ASCE 7-16 wind loads could fail if local snow load amendments require closer purlin spacing. Staying compliant means cross-referencing at least six different code documents on every project—but getting it right prevents costly rework and keeps systems safe for decades.