Installation of solar PV modules, mounting systems and cabling
Mounting systems
On-roof systems use roof hooks fixed into rafters or battens, with flashing to keep the roof watertight, then aluminium rails and mid/end clamps. Respect the manufacturer's clamp zones - typically within a defined band 200–450 mm from the module edge - because clamping outside the zone can void the warranty and stress the frame. Torque fixings to the stated value, leave the specified ventilation gap beneath the modules, and consider wind uplift at ridges, verges and corners. Ground and flat-roof systems add ballast or penetration design considerations.
DC cabling and connectors
Use double-insulated, UV-stable DC cable of a suitable temperature rating, clipped and supported clear of the roof surface, with drip loops and no water traps. Keep cable runs as short as practicable to limit voltage drop and minimise roof penetrations; avoid leaving mated connectors lying on the roof. Only mate connectors from the same manufacturer and type - mixed MC4-style connectors are a classic failure and fire risk. Crimp with the correct tool and pull-test. Cable must be protected from animals, abrasion and foot traffic, and routed away from hot flues.
Earthing, bonding and labelling
Bond module frames and mounting rails to the main earthing terminal with a suitably sized conductor (typically 4 mm² minimum, larger where lightning protection is bonded), using star washers to bite through anodising. Label the DC cables, the array, the isolators, and place a dual-supply warning notice at the origin, the consumer unit and the inverter.
Rule of thumb
A four-module array of 22 kg modules is about 88 kg spread across roughly 6–7 m² - around 13–15 kg/m². Light for the roof, but each hook may carry a significant share, so calculate per fixing, not per square metre.
Traps
Clamping outside the permitted zone; mixing connector brands; assuming the module frame is earthed through the rail; leaving cable in contact with the roof covering.