Fronius string inverters — the Primo, Symo, and older Galvo series — display faults as numbered state codes on the built-in screen or through the Fronius Solar.web monitoring portal. Here’s what the most frequently reported ones mean.
Common Fronius Error Codes
State 509 (Arc Fault Detected): A safety-related fault, not a routine performance code. See our full guide on arc fault errors for details on what triggers this and why it’s urgent.
State 305 / 306 (Insulation Fault): Indicates reduced insulation resistance in the DC circuit — commonly from moisture, damaged conduit, or degraded connectors at the panel level.
State 516 (Grid Voltage Fault): The inverter has detected grid voltage outside its acceptable operating window. Occasional occurrences are often utility-side; frequent repeats warrant a technician visit to rule out a wiring issue.
State 480s (Internal Hardware Fault): A broad category covering internal component issues — often the fan, internal sensors, or power stage. Frequently seen on Galvo and early Primo units approaching 10+ years of service.
Display Blank, No Codes: Suggests a complete loss of power to the display or control board — a hard failure requiring on-site diagnosis.
Repair or Replace?
Fronius inverters carry a standard warranty of 5-10 years depending on series and purchase date, extendable on some models. Fronius units are generally well-supported for parts availability, making targeted repair (fan, power board) a viable option even outside warranty — but full replacement becomes more cost-effective once a unit is approaching or past 12-15 years old.
Related Reading
- Inverter Errors & Failures: Complete Troubleshooting Guide
- Solar Arc Fault Errors: Causes, Risks & What to Do
- Your String Inverter Is Failing: Repair, Replace, or Upgrade?
Get Your Fronius System Diagnosed
ElectriCare services Fronius Primo, Symo, and Galvo inverters, including warranty documentation support and full replacement when repair isn’t cost-effective.
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