A solar mounting system comprises hundreds or thousands of bolted connections, and a single improperly installed bolt can lead to bracket loosening, module drop, or even array collapse. Standardized installation procedures and precise torque control are fundamental to ensuring 25-year structural safety. This article systematically reviews solar fastener installation requirements based on GB 50794-2012, IEC 62939, and AS/NZS 5033 standards.
Solar mounting installation should follow the principle of "primary before secondary, bottom before top": first install bolts connecting posts to foundation embedments, then bolts connecting main beams (purlins) to posts, and finally module clamps to rails. Before installation, verify bolt specifications (commonly M8×25, M10×30, M12×40 Grade 8.8 hot-dip galvanized hex bolts) and inspect threads for damage and zinc coating for chipping. Bolts should be inserted in a consistent direction (typically inside-out, bottom-up), with flat washers and spring washers on the nut side (or flange bolts as an alternative). In regions with seismic design intensity 7 or above, post-to-foundation connections must use double nuts for locking.
Per GB 50794 and mounting design documents, recommended torque values for common Grade 8.8 bolt sizes are: M8 at 20–25 N·m, M10 at 33–40 N·m, M12 at 55–65 N·m, and M16 at 125–145 N·m. Stainless steel bolts (A2-70/A4-70) require approximately 70–80% of the torque of equivalent Grade 8.8 carbon steel bolts—for example, M10 stainless steel bolts at 25–32 N·m. Torque must be applied with calibrated torque wrenches (accuracy within ±3%); ordinary wrenches used by feel are strictly prohibited. A two-step "snug-tight + final-tight" method is recommended: snug torque at 50% of final value to seat the connection, then final torque to design value, followed by marking (a straight line across bolt-nut-connector with a marker pen for later loosening inspection).
Solar mounts endure sustained wind loads (design basic wind pressure typically 0.45–0.75 kN/m²) and thermal stress, making bolt locking critical. Common locking solutions include: spring washers (most economical, suitable for static loads), flange bolts (increased friction), nylon insert lock nuts (nylon ring engages threads, effective for vibration, but service temperature ≤120°C), and Spiralock threads (30-degree wedge thread, optimal seismic locking performance at higher cost). Module clamp bolts are recommended with flange bolts + nylon insert lock nuts. Acceptance criteria follow GB 50205: final torque deviation must be within ±10%, with sampling inspection of no less than 10% and no fewer than 10 sets per batch; connection contact surfaces must be tight, with 0.3mm feeler gauge insertion depth not exceeding 20mm; all bolts must expose no fewer than 2 thread pitches. Completion acceptance requires submission of bolt material certificates, torque inspection records, and concealed work acceptance forms.