Commissioning, Maintenance, and Troubleshooting
Domain 5 tests verification, documentation, and diagnosis: proving a system is safe and performing, then finding faults fast when production drops.
Commissioning sequence
- Visual inspection: labeling, clearances, torque marks, strain relief, flashing.
- Insulation resistance (megohmmeter) on each string before inverter connection; expect at least 1 MΩ at the specified test voltage.
- Open-circuit voltage and short-circuit current per string, compared to expected temperature-corrected values.
- Polarity and rapid shutdown test - confirm array-boundary conductors reach the required voltage limit within the specified time.
- Inverter startup, anti-islanding and grid-profile verification, monitoring setup, and a signed commissioning report.
Maintenance
- Annual visual inspection and torque checks; thermal imaging finds hot spots, failing bypass diodes, and loose terminations.
- Clean with soft brushes and low-mineral water; no abrasives or high-pressure spray on frames and connectors.
- Inspect connector pairs for corrosion and full engagement. Do not mate MC4-type connectors from different manufacturers.
Troubleshooting
A string with normal voltage but low current points to soiling, shading, or a failed substring. A string low by roughly one module's Voc points to an open circuit or disconnected module. Repeated GFDI trips mean a real ground fault - never simply reset and walk away.
Worked example
At 20 °C, expected module Voc ≈ 41.2 × 1.0145 ≈ 41.8 V, so a 12-module string should read about 502 V. The meter shows 460 V. The 42 V deficit equals one module's Voc, pointing to an open connector or failed module. Isolate the string, measure each module's Voc, and check every connector for full engagement before replacing anything.
Traps
- Diagnosing from a single low-irradiance morning reading.
- Resetting a GFDI without locating the fault.
- Cleaning with hard water or abrasives that etch glass and coatings.