Mounting Structures and Mechanical Installation: Roof and Ground Mounts, Clamps, Wind Load and Handling
This section covers mounting structures and mechanical installation: roof and ground mounting, rails and clamps, structural safety, wind-load basics and correct module handling. The exam tests whether the array stays attached and waterproof for 25 years.
Structure types and loads
Roof systems use rails fixed to rafters or purlins, with flashed penetrations sealed against rain. Flat roofs often use ballasted or elevated structures; ground mounts use concrete pads, rammed piles or ground screws. Design for dead load, live load and wind uplift. In India, wind load follows IS 875 (Part 3); basic wind speed depends on location and terrain.
Clamps, rails and corrosion
Rails run perpendicular to supports and within the manufacturer's mounting zones. Clamps must sit in permitted zones, usually not at the extreme frame edge, and be torqued to the datasheet value. Use stainless or hot-dip galvanised fasteners; isolate aluminium from bare steel or concrete to limit galvanic corrosion. Allow thermal expansion.
Wind and handling
Uplift pressure acts on the module area; calculate force as pressure × area and check anchors with a safety factor. Keep edge clearance low where specified. Carry modules vertically with two people, never lift by cables or junction box, do not walk on glass, store on edge on soft pads, and stop installation in high wind.
Worked example
A 2.0 m² module sees a design wind pressure of 1.2 kN/m². Uplift = 1.2 × 2.0 = 2.4 kN. With four clamps and a safety factor of 2, each anchor must resist 2.4 × 2 ÷ 4 = 1.2 kN. If the datasheet allows only 0.8 kN per clamp at that span, add rails or clamps.
Traps
Clamping outside the allowed zone; mixing stainless bolts with aluminium rails without isolation; blocking roof drainage; ignoring thermal expansion; carrying modules by the junction box; leaving roof penetrations unsealed.