Installation
Execution details that get inspected
Installation quality lives in three places: the roof attachment, the conductor management, and the bonding. Each has a manufacturer instruction that overrides habit.
Roof attachments must land on structure or on listed standoffs spanning to structure, flashed in the correct shingle course, with sealant as a secondary seal only. Rail spans, cantilevers, and clamp zones come from the racking engineering report; mid-clamps and end-clamps have different torque values and different allowed positions on the module frame. Respect the module's clamping zone drawing and keep clamps clear of junction boxes and frame drainage slots.
Conductor management means sunlight-resistant, wet-location-rated conductors where exposed, listed connectors of the same model mated only to each other, drip loops before entering conduit, expansion provisions, and no routing where water pools or where the conductor abrades on the roof surface. Keep connectors off the roof deck.
Bonding requires a continuous equipment grounding path: listed bonding hardware through rail splices, star washers or listed WEEB-style devices where approved, and a properly sized equipment grounding conductor run with the circuit.
Traps
- Over-torquing clamps and cracking module frames or glass.
- Placing a rail splice where the span table does not allow it, or cantilevering too far past the last attachment.
- Mixing connector brands or using field-crimped connectors with the wrong die.
- Skipping bonding jumpers across rail splices and at rapid shutdown devices.
- Using indoor-rated or non-sunlight-resistant wire in exposed rooftop runs.
- Setting an inverter too close to the roof deck or blocking required working clearance.
Worked example
A racking report lists an 8 ft attachment-to-attachment span. Common manufacturer limits allow cantilever of roughly one-quarter to one-third of the span, so 2 ft maximum past the last attachment. With a 20 ft rail you get three bays (8+8) plus 2 ft cantilevers at each end: 24 ft of coverage. Verify the actual listed cantilever before building; the exam will test that you look it up rather than assume.
Rule of thumb
Torque every structural and bonding fastener to the printed specification with a calibrated tool, and record the value in the commissioning file.