CSLB C-46 Solar ContractorPhotovoltaic System InstallationEasy
A homeowner reports that their newly installed grid-tied PV system is not producing power, despite clear skies. The inverter display shows a 'Grid Fault' error code. The utility grid is confirmed to be operational. Which of the following is the MOST likely cause of this error?
- AShading on a portion of the PV modules.
- BInsufficient DC voltage from the PV array.
- COver-temperature shutdown of the inverter.
- DIncorrectly wired AC disconnect switch.
Show answer & explanationAnswer & explanation
Correct answer: D. Incorrectly wired AC disconnect switch.
A 'Grid Fault' error on a grid-tied inverter, when the grid is confirmed operational, most commonly indicates an issue with the inverter's connection to the grid, such as an incorrectly wired or open AC disconnect switch, or a utility-side issue like an open breaker.
Why the other options are wrong
- A. Shading would reduce power output but generally not cause a 'Grid Fault' unless it severely drops DC voltage below the inverter's operating threshold, which would present as a DC-side error.
- B. Insufficient DC voltage would typically result in a 'Low DC Voltage' or 'MPPT Out of Range' error, not a 'Grid Fault'.
- C. Over-temperature would typically show a thermal error, not a 'Grid Fault'.
Grid Fault Error
An inverter error indicating a problem with the connection to, or conditions of, the utility grid.
- Prevents inverter from feeding power to the grid.
- Can be caused by open AC disconnects, utility outages, or incorrect grid parameters.
- Requires verifying AC connections and utility status.
Memory trick: Grid Fault means check the 'AC-side' first, from inverter to meter!