A Fronius inverter error code list is usually a list of State Codes, the numbered diagnostic messages used by Fronius Primo, Symo, Eco, GEN24 Plus, and related systems. The code identifies a grid condition, operating state, communication issue, or hardware fault, but the exact meaning can vary by inverter family, firmware, and national grid settings.
Key facts
Fronius calls inverter diagnostic numbers State Codes, rather than using one universal error-code system.
State 102 commonly indicates excessive AC grid voltage, while State 103 commonly indicates insufficient AC voltage.
States 306 and 307 can be normal at dawn, dusk, or during insufficient solar irradiance.
State 475 indicates an insulation or ground fault in the photovoltaic DC circuit and requires electrical safety precautions.
A Solar.web outage does not automatically mean the inverter has stopped producing electricity.
The inverter model, full code, timestamp, and firmware version are necessary for reliable diagnosis.
What Are Fronius State Codes?
Fronius State Codes are numeric diagnostic identifiers generated when an inverter detects a measured condition outside its operating limits or records an event that needs attention. The inverter evaluates AC voltage, AC frequency, DC voltage, insulation resistance, temperature, internal communications, grid synchronisation, and data connections.
Fronius documentation uses the term “state codes” for these displayed diagnostic conditions. A code is not always a component failure. Some codes describe a temporary operating state, such as insufficient sunlight, a grid interruption, or a controlled reduction in output.
The number alone is therefore incomplete evidence. A reliable diagnosis combines the code with the inverter family, whether the message is active or historical, the time of day, production data, and whether the message repeats after conditions return to normal.
Does the code number have the same meaning on every Fronius inverter?
No. The same or similar number should not be interpreted identically across all Fronius platforms without checking the relevant Fronius documentation. SnapINverter models such as Primo and Symo use a different interface and code context from GEN24 Plus systems, while Verto models may expose events through a newer web or app interface.
National grid rules also affect voltage and frequency thresholds. A 230-volt installation in Australia, for example, is assessed under local settings associated with AS/NZS 4777.2, while other countries use different regulatory profiles. That difference can change when a grid event is triggered.
How Does a Fronius Inverter Detect a Fault?
A Fronius inverter continuously samples electrical and thermal parameters, compares those values with configured safety limits, and records a State Code when a limit or sequence test fails. The inverter may stop exporting, reduce output, continue operating with a warning, or disable only a communications function.
The response depends on the affected subsystem. A grid-frequency event can cause a temporary disconnection, whereas a Solar.web communication failure may leave generation unaffected. An insulation fault is treated more seriously because DC leakage can create shock, fire, or equipment risks.
| Monitored subsystem | Example measurement | Typical response | Relevant states |
|---|---|---|---|
| AC grid voltage | 230 V nominal system, 253 V upper example | Disconnect or reduce output | 102, 103, 567 |
| AC grid frequency | 50 Hz or 60 Hz profile | Pause grid feed-in | 105, 106, 108 |
| PV DC input | Start-up voltage and string current | Remain idle or report low input | 306, 307 |
| Internal temperature | Heat-sink temperature | Derate or stop for cooling | 303, 304 |
| Insulation resistance | DC-to-earth leakage condition | Prevent start-up or stop operation | 475 |
| Internal communications | Board-to-board data exchange | Fault shutdown or restart request | 401 |
| Monitoring connection | Solar.web data path | Monitoring interruption | 999 |
Where Can You Find a Fronius Error Code?
The correct lookup method depends on the interface installed on the inverter. SnapINverter units commonly show State Codes on their front display, while GEN24 Plus and some newer units rely on LEDs, Solar.web, or the local web interface.
SnapINverter display method
For a Primo, Symo, or Eco with an integrated display:
- Stand in front of the inverter and read the status screen.
- Press the Enter button on the front panel.
- Look for the line beginning with STATE followed by the number.
- Press Enter again to cycle through additional active or queued messages.
- Photograph every code before clearing or restarting the unit.
A single inverter can record more than one condition. The first displayed code may not identify the original cause, particularly when a grid interruption produces secondary communication or startup messages.
GEN24, Verto, and LED-only method
For a GEN24 Plus or LED-only model, use Solar.web first. Open the relevant system, select the inverter, and inspect the events, service messages, or component information. Menu labels can change with firmware and account permissions, so the event timestamp and full text matter more than an assumed menu path.
A local connection may also be available through the inverter’s Wi-Fi access point. On many Fronius models, activating the front optical sensor or communication control starts an access point with a name beginning FRONIUS_. The commonly documented local address is 192.168.250.181, but installers may have changed the network arrangement.
| Platform | Primary code source | Display style | Useful supporting record |
|---|---|---|---|
| Primo with SnapINverter display | Front LCD | STATE number | Solar.web event timestamp |
| Symo with SnapINverter display | Front LCD | STATE number | Grid voltage and frequency |
| GEN24 Plus | Solar.web or local interface | LED status bar | Firmware and component details |
| Verto | Solar.web or local interface | LED or web status | Installation serial number |
| Any model with monitoring | Solar.web events | App or browser message | Production graph and outage time |
Fronius Inverter Error Code List by Category
The following list provides the common interpretation of frequently searched Fronius State Codes. It is a practical field reference, not a substitute for the model-specific Fronius service documentation.
| State Code | Common meaning | Likely system response | First action |
|---|---|---|---|
| 102 | AC grid voltage too high | Disconnects from grid | Record time and ask installer to review voltage |
| 103 | AC grid voltage too low | Disconnects from grid | Check for local outage or brownout |
| 105 | AC frequency too high | Temporarily stops feed-in | Wait for grid recovery, then check recurrence |
| 106 | AC frequency too low | Temporarily stops feed-in | Check utility supply and event frequency |
| 108 | Islanding or unreliable grid | Prevents unsafe energisation | Confirm AC isolator and utility status |
| 303 | Temperature or heat-sink operating limit | Output reduction or stop | Check airflow and ambient heat |
| 304 | Thermal protection condition | Derating or shutdown | Remove external obstruction, call service if repeated |
| 306 | PV power too low | Remains idle | Normal at night or in very low light |
| 307 | DC input voltage too low | Does not start generation | Check whether the message occurs in daylight |
| 401 | Internal communication problem | May stop production | Capture code and arrange service if persistent |
| 443 | Power-stage or fan-related fault | May stop or limit operation | Do not open the enclosure |
| 475 | Insulation or ground fault | Prevents safe operation | Stop investigating live DC circuits and call an electrician |
| 482 | Startup incomplete | Fails to complete boot | Record firmware and restart only if authorised |
| 509 | No energy fed to grid for 24 hours | Warning recorded | Check production, AC breaker, and shading |
| 567 | Grid-voltage-dependent reduction | Continues at reduced output | Review voltage logs and utility capacity |
| 731 | USB initialisation or data issue | Firmware or data task may fail | Remove unsupported USB media if safe |
| 733 | Data communication or USB error | Update or logging may fail | Use installer-approved firmware media |
| 999 | Monitoring communication interruption | Solar.web data missing | Check internet, router, and inverter connection |
| 1001 | GEN24 insulation measurement or diagnostic process | Temporary operating interruption | Check event text and allow the test to finish |
What do States 102, 103, 105, 106, and 108 mean?
States 102, 103, 105, 106, and 108 generally indicate that the inverter cannot verify acceptable AC grid conditions. State 102 is associated with high voltage, State 103 with low voltage, States 105 and 106 with frequency outside the configured range, and State 108 with a suspected islanding or stand-alone condition.
The inverter disconnects because grid-connected solar equipment must not continue energising a circuit that may be isolated from the utility. A brief event after a blackout can be normal. Repeated events during strong sunlight are different because they can reduce annual yield and may indicate a high-voltage network problem, undersized conductors, a loose connection, or excessive voltage rise between the inverter and connection point.
For a 230-volt system, 253 volts is a commonly discussed upper reference in Australian troubleshooting, but the actual trip and reconnection values depend on the configured standard and measurement conditions. Do not adjust protection settings yourself.
What do States 303, 304, 306, and 307 mean?
States 303 and 304 relate to thermal operating limits, while States 306 and 307 generally indicate insufficient photovoltaic input. States 306 and 307 are often normal when the sun is below the usable generation threshold, but the same messages at midday require investigation.
Thermal events become more likely when the inverter has restricted airflow, is exposed to direct summer sun, is installed near another inverter’s exhaust, or has an obstructed fan. Output derating is a protective response, not proof that the inverter has failed.
| Situation | Code more likely | Normal interpretation | Escalation point |
|---|---|---|---|
| 7:00 PM in winter | 306 or 307 | Insufficient irradiance | None if production graph is normal |
| Heavy snow or dense shading | 306 or 307 | PV input below start threshold | Inspect panels when safe |
| 40°C outdoor temperature | 303 or 304 | Thermal derating possible | Repeated midday events |
| Clear midday conditions | 307 | DC string or isolator issue possible | Installer inspection |
| Inverter beside hot exhaust | 303 or 304 | Installation airflow problem | Correct clearance and ventilation |
| Cool morning with no output | 303 or 304 | Less typical | Service diagnosis if persistent |
What do States 401, 443, 475, and 482 mean?
States 401, 443, 475, and 482 deserve faster attention because they can involve internal communications, power electronics, cooling, insulation, or incomplete start-up. State 475 is especially important because the fault may be located in a panel cable, connector, junction box, array frame, or moisture-affected roof circuit rather than inside the inverter.
Do not remove inverter covers, disconnect MC4 connectors, test live strings, or bypass an isolator. Photovoltaic modules can produce hazardous DC voltage whenever light reaches them, even when the AC supply is off.
State 401 may indicate a board communication timeout. State 443 is commonly associated with an energy-transfer or power-stage condition, and some model-specific documentation links similar events with fan operation. State 482 can follow an interrupted boot or firmware process. These meanings require confirmation against the exact product family.
What do States 509, 567, 731, 733, 999, and 1001 mean?
States 509, 567, 731, 733, 999, and 1001 do not all indicate the same level of danger. State 509 warns that no energy reached the grid during a 24-hour period, State 567 indicates voltage-dependent power reduction, States 731 and 733 concern USB or data processes, State 999 usually concerns monitoring communication, and State 1001 is associated with a GEN24 diagnostic or insulation measurement event.
A 509 warning can result from snow, heavy soiling, a tripped AC breaker, a prolonged outage, or a system that never reached its export threshold. A 567 event matters financially because the inverter may remain online while producing less than the array could deliver. Ask an installer to compare inverter-side voltage with the utility connection voltage and review the production graph.
Which Fronius Codes Are Normal at Night?
States 306 and 307 can be normal at night because the photovoltaic array is not receiving enough irradiance to reach the inverter’s operating or start-up voltage. A night-time 306 or 307 message should not trigger a service call when the system resumes normal generation after sunrise.
The time pattern is the diagnostic clue. A code that appears at dusk and clears after sunrise is usually an operating condition. A code that remains during clear midday weather, affects only one inverter, or coincides with zero production may indicate a disconnected string, failed isolator, damaged cable, shading, or an array configuration problem.
State 509 requires more context. It records a 24-hour lack of grid export, so a system can generate some energy yet still create the warning if export was prevented for the remainder of the day.
How Do You Safely Reset a Fronius Inverter?
A qualified person should perform an AC and DC restart using the model’s documented procedure. The typical sequence takes approximately 5-10 minutes, but a restart is appropriate only for transient states, not for smoke, burning smells, damaged equipment, exposed wiring, water ingress, or an insulation fault.
- Switch off the solar AC supply at the designated switchboard isolator or circuit breaker.
- Turn the inverter’s DC isolator to 0, if the installed model has an accessible isolator.
- Wait at least 3-5 minutes, or follow the exact Fronius manual for that model.
- Turn the DC isolator back to I.
- Restore the solar AC supply.
- Allow up to 2-3 minutes for start-up checks and grid synchronisation.
- Confirm that the code clears and that production appears in Solar.web.
You will know the restart helped when the inverter completes its normal LED or display sequence, reconnects to the grid, and begins registering power without the same active State Code. A restart that clears a code briefly but produces it again is diagnostic evidence, not a permanent repair.
When should you avoid a reset?
Avoid resetting State 475, repeated internal hardware faults, visible damage, water entry, smoke, arcing, or a strong electrical smell. Keep clear of the equipment and contact the installer or licensed electrician. A reset can erase useful timing information without correcting the failed insulation, connector, fan, board, or grid condition.
SnapINverter, GEN24, and Verto: What Changes?
SnapINverter, GEN24 Plus, and Verto systems share the Fronius State Code concept, but their user interfaces, battery functions, communications hardware, and service procedures differ. SnapINverter models commonly provide a physical LCD, while GEN24 and Verto installations rely more heavily on LEDs, Solar.web, and local web access.
| Feature | SnapINverter Primo | SnapINverter Symo | GEN24 Plus | Verto |
|---|---|---|---|---|
| Typical phase arrangement | Single-phase | Three-phase | Single or three-phase model dependent | Three-phase family |
| User interface | Front LCD and buttons | Front LCD and buttons | LED and web interface | LED and web interface |
| Battery capability | Model and add-on dependent | Model and add-on dependent | Hybrid models available | Model dependent |
| Code retrieval | Inverter display | Inverter display | Solar.web or local interface | Solar.web or local interface |
| Common service need | Grid and fan diagnosis | Grid and phase diagnosis | Firmware and battery integration | Commissioning and network diagnosis |
SnapINverter troubleshooting is often faster on site because the display exposes the active code without a network connection. GEN24 provides richer digital information for storage and energy-management systems, but a weak home network can make a healthy inverter appear unavailable in Solar.web.
Neither platform is automatically easier to repair. SnapINverter units may be older and outside warranty, while GEN24 systems involve firmware compatibility, battery settings, backup circuits, and digital commissioning.
What Should You Record Before Calling for Service?
Record the exact State Code, inverter model, serial number, firmware version if visible, date and time, LED pattern, and whether the code is active or historical. A photograph of the display or Solar.web event often saves a second visit.
Also record weather, approximate outdoor temperature, grid outage information, production at the time, and whether the code affects one inverter or several. Repeated State 102 events across multiple nearby inverters suggest a network voltage issue more strongly than a single-unit electronics failure.
| Information to capture | Example value | Why it matters |
|---|---|---|
| Inverter model | Fronius Symo 10.0-3-M | Narrows the documentation set |
| State Code | 102 | Identifies the event family |
| Timestamp | 12 January, 13:42 | Matches utility and production logs |
| AC voltage reading | 257 V at inverter | Supports voltage-rise diagnosis |
| Production status | 4.8 kW before trip | Shows operational impact |
| Firmware version | 1.34.2-1 | Identifies software-specific behavior |
| Serial number | Rating-plate value | Required for warranty and Solar.SOS |
What Do Fronius Repairs Typically Cost?
Typical out-of-pocket costs range from approximately $150-$250 for a local diagnostic or firmware visit and $250-$400 for a fan replacement, while a complete out-of-warranty inverter replacement can exceed $1,800. Prices vary by country, access, inverter size, warranty status, travel, and whether a licensed electrician is required.
The figures below are practical indicative ranges, not Fronius price guarantees. A grid-voltage problem may cost the homeowner nothing when the distribution network operator accepts responsibility, but collecting evidence and obtaining a network adjustment can take several weeks.
| Action | Typical cost in AUD | Typical timeframe | Usual responsibility |
|---|---|---|---|
| Remote firmware support | $0 | 15-30 minutes | Installer or Fronius portal |
| On-site diagnostic visit | $150-$250 | 1-2 hours | Installer or electrician |
| Internal fan replacement | $250-$400 | 1-3 business days | Service provider |
| Grid voltage investigation | $0-$300 | 2-4 weeks | Utility or DNSP, case dependent |
| Warranty board replacement | $0 for covered parts | 3-7 business days | Fronius service partner |
| New inverter installation | $1,800-$3,500 or more | 1-3 business days | Installer and electrician |
Common Mistakes When Reading State Codes
Treating every number as a hardware failure
Codes 306 and 307 often appear during normal low-light periods. Check the time and production graph before booking a repair.
Replacing an inverter for State 475
An insulation fault can be on the roof array or DC cabling. Replacing the inverter first may leave the hazardous condition untouched.
Ignoring repeated State 102 events
One brief voltage event may be temporary. Repeated midday events justify voltage logging because ongoing disconnection can reduce yield and may identify a network or installation fault.
Blaming Solar.web for no generation
State 999 usually concerns monitoring communications. Check the inverter LEDs and local production before concluding that the power-conversion equipment has stopped.
Using unofficial firmware media
States 731 and 733 can follow incompatible, corrupted, or improperly prepared USB media. Firmware installation should use Fronius-approved files and installer procedures.
Assuming a reset proves the repair worked
A temporary restart can clear a symptom while the underlying fault remains. The meaningful checkpoint is stable operation across the next generation period, not merely a blank display immediately after reboot.
Expert Rules for Faster Diagnosis
Rule one: compare code timing with sunlight. A code at 6:00 PM has a different probability distribution from the same code at noon under clear skies. Time-of-day evidence separates expected PV behavior from string or inverter faults.
Rule two: compare multiple inverters. If several units disconnect within the same minute, investigate the shared AC network, utility supply, or site protection before replacing individual inverters.
Rule three: distinguish energy loss from data loss. A missing Solar.web graph proves that cloud data is absent, not that the inverter produced zero energy. Use the local display, meter, or inverter status LEDs to separate monitoring failure from generation failure.
When Should You Call an Installer or Electrician?
Call a licensed solar electrician promptly for State 475, repeated 401 or 443, persistent 482, visible damage, overheating, water ingress, electrical odour, arcing, or any code that remains after documented recovery conditions return. Contact the utility or distribution network operator when repeated high or low grid-voltage events affect the system.
Homeowners can safely inspect the Solar.web event log, check whether the solar AC breaker has tripped, note the code, and observe external airflow without opening the inverter. They should not test live DC conductors, remove covers, alter grid settings, bypass protection, or disconnect rooftop connectors.
FAQ
How long does a Fronius inverter take to reconnect after a grid fault?
A Fronius inverter commonly waits through a safety verification and grid-synchronisation period before resuming export. The visible restart cycle often takes 2-3 minutes after power returns, but local grid standards can impose longer reconnection delays. Repeated disconnections after reconnection indicate an ongoing grid or installation condition.
Why does my Fronius inverter show 102 every sunny day?
State 102 usually means the inverter measures AC voltage above its configured limit. Daily sunny-weather recurrence can result from voltage rise in the cable run, a high local network voltage, shared export congestion, or a connection issue. Have an installer capture voltage logs at the inverter and grid connection, then involve the utility if appropriate.
Can I clear a Fronius State Code without an electrician?
You can record the message, check the monitoring connection, inspect the external AC breaker, and follow the manufacturer’s documented restart procedure when no safety hazard exists. You cannot safely diagnose live DC faults, insulation faults, internal boards, or altered grid settings without qualified electrical training and authorisation.
Is State 999 a failed inverter?
State 999 usually indicates that monitoring data has not reached Solar.web for an extended period, not that the inverter has stopped converting solar energy. Check the inverter’s local LEDs, display, household meter, router, and internet connection. If the inverter also shows a hardware or grid code, treat that separate code as the primary diagnosis.
What does Fronius State 475 mean?
State 475 generally indicates an insulation or ground fault in the photovoltaic DC system. The source may be a damaged cable, wet connector, panel junction box, array frame, or inverter-side circuit. Do not touch exposed wiring or disconnect rooftop connectors. Arrange a licensed electrical inspection before attempting a restart.
Should I replace my Fronius inverter after one error code?
No. A single temporary grid, low-light, communications, or thermal code does not justify replacement. Replacement becomes more reasonable when a qualified diagnosis confirms an uneconomic hardware fault, the unit is outside warranty, repair parts are unavailable, or repeated faults continue after the array, wiring, grid, cooling, and firmware have been checked.
The Bottom Line
The most useful Fronius inverter error code list is a model-specific State Code reference paired with timing, production, voltage, and event-log evidence. States 306 and 307 can be normal in darkness, States 102 and 567 point toward grid-voltage investigation, State 999 often affects monitoring only, and State 475 requires electrical safety action. Record the complete code and inverter model before resetting or requesting service.