Fronius inverters (Primo, Symo, Eco, GEN24, Tauro) display a status code on the display, on the web interface and on Fronius Solar.web when they detect anything out of the ordinary. Most of these are alerts that resolve themselves; others indicate a problem with the installation (grid, solar array, cabling); and a few require intervention by the technical support team. This guide organises them by series and tells you what to check in each case.
| Code | Meaning | What to do |
|---|---|---|
| 102 | Mains voltage too high | Common in rural areas or areas with a high concentration of solar panels. Check the voltage at the connection point and the cross-sectional area of the AC cable leading to the distribution board. If it regularly exceeds 253 V, notify the distribution company. |
| 103 | Mains voltage too low | Voltage drops on the line or an undersized AC cable. |
| 104 | Unstable mains voltage | It usually accompanies 102/103. |
| 105 | Mains frequency too high | Check the country/standard configured for the network (Spain: RD 244 / UNE 217002). |
| 106 | Frequency too low | Ditto. When using a generator, the frequency is often outside the tolerance range. |
| 107 | Signal outside the permitted range / no signal | The inverter is not detecting the mains supply or is out of range. Check the inverter’s AC circuit breaker and ensure that all three phases are present (Symo). |
| 108 | Detection of island operation | The inverter believes it is supplying an isolated grid. This may occur on very weak grids; if it happens repeatedly, please contact support. |
All the codes in this series are auto-reset: the inverter only reconnects once the grid has stabilised. They are only a problem if they occur on a daily basis and affect output.
| Code | Meaning | What to do |
|---|---|---|
| 301 | AC overcurrent | It resets automatically. If the problem persists, check the network. |
| 302 | DC overcurrent | Check the solar array: there are more panels connected in parallel than the MPPT can handle. |
| 303 / 304 | DC/AC module overtemperature | Insufficient ventilation or direct sunlight on the inverter. Clean the vents and ensure the distances specified in the manual are observed. |
| 305 | No power is supplied even though the relay is closed | Restart the inverter. If the problem persists, contact SAT. |
| 306 | Insufficient PV power (LOW PV OUTPUT) | Normal at dawn, dusk and when there are thick clouds. |
| 307 | Insufficient DC voltage (LOW PV VOLTAGE) | Normal at the start and end of the day. In direct sunlight, this indicates a disconnected string, a blown fuse or a Voc below the MPPT minimum. See My Fronius isn’t working. |
| 308 | Intermediate circuit voltage too high | Automatic restart. If the problem persists, contact SAT. |
| 309 / 313 | Input voltage too high at MPPT1 / MPPT2 | There are more panels in the string than the inverter can handle (maximum 1,000 V for the Primo/Symo models, 600 V for the GEN24 model, depending on the model). Correct the string before the equipment is damaged. |
| 314 / 315 | Calibration error / current sensor | SAT. |
| 325 | Overheating in the connection area | AC/DC terminals are not tightened properly or are of insufficient cross-section. Check whilst the equipment is switched off. |
| 326 / 327 | Fan failure | Clean the fan; if it does not turn, replace it (this is a common spare part for the Primo/Symo models). |
These codes indicate a fault between the power stage and the inverter control unit. The first step is always to full reset (AC and DC switched off for 5 minutes). If the error code reappears, you must raise a ticket with the SAT.
| Code | Meaning |
|---|---|
| 401 | No communication with the power stage |
| 406 / 407 | Faulty temperature sensor |
| 408 | A direct current injection has been detected in the grid |
| 412 | Fixed voltage mode instead of MPP (check the setting in the menu – this is not a fault) |
| 415 | Safety shutdown via optional card or Datamanager |
| 416 | No communication between the power stage and the control stage |
| 417 / 419 | Hardware identification conflict (common after replacing a power amplifier stage) |
| 420 | No communication with the Hybrid Manager (GEN24 with battery) |
| 425 | No communication with the power stage |
| 431 / 436 / 438 | Software incompatibility: update the firmware (see how to update) |
| 443 | Low or asymmetrical intermediate circuit voltage |
| 447 / 475 | Insulation fault in the solar array (see 502) |
| 448 | Neutral not connected (Symo three-phase): check terminal N |
| 457 | Network relay stuck or neutral-to-earth voltage too high |
| 463 | Reversed AC polarity: check L and N |
| 474 | Faulty RCMU sensor |
| 476 | Driver supply voltage too low |
| 480 / 481 | Functional incompatibility: firmware |
| 482 | Set-up interrupted: repeat the initial wizard |
| 489 | Persistent overvoltage in the intermediate circuit |
| Code | Meaning | What to do |
|---|---|---|
| 502 | Insulation fault in the panels | Moisture in MC4 connectors, stripped cable or a panel with a ground fault. This mainly occurs in the morning when there is dew and disappears once it dries out. If the problem persists, the insulation resistance of each string must be measured. |
| 509 | No injections in the last 24 hours | The inverter has not been generating power for a day: the DC disconnector is open, the fuses have blown, there is snow, or the inverter is in standby mode. |
| 515 | No communication with the filter | Restart; if the problem persists, contact SAT. |
| 516 | No communication with the storage unit | GEN24 with battery: check the communication cable connected to the battery and its power supply. |
| 517 | Temperature-dependent derating | The inverter reduces power output to protect itself. Improve ventilation. |
| 518 | Internal ruling by the DSP | SAT. |
| 520 | No communication with the power stage | SAT. |
| 522 / 523 | Low DC voltage in string 1 / string 2 | One string is producing less than the other: shadow, blown fuse, loose connector or damaged panel. Compare the curves for each MPPT on Solar.web. |
| 558 / 559 / 564 | Functional incompatibility | Update the firmware. |
| 560 | Power reduction due to over-frequency | Regulatory requirement: the inverter reduces power output when the grid frequency rises above 50.2 Hz. |
| 566 | Arc detector deactivated | For information purposes only (models with AFCI). |
| 567 | Power reduction due to mains voltage | The inverter cuts out to prevent the mains voltage from rising any further. If this happens regularly, check the AC wiring or ask your electricity supplier to adjust the transformer. |
| 568 | No communication with the smart meter | Check the Modbus RTU cable, the terminating resistor and the meter’s address. See Smart Meter and feed-in 0. |
Codes such as 601 (CAN bus full), 701–704 (start-up information), 705–716 (memory and clock) or 721–728 (data log) are for information purposes only. If they appear in isolation, no action is required. If error codes 705/706 (memory error) recur after a reset, the inverter must be checked.
FV Componentes is Fronius authorised technical service centre (Fronius System Partner). If the problem persists after carrying out these checks, please open a ticket at Technical support with the serial number and a screenshot of Solar.web, and we’ll diagnose it.
Ways to update the firmware on a Fronius inverter: via Solar.web, via the local web interface, and via USB on SnapINverter models. Why update, available versions, and how to register your inverter to extend the warranty to 5 years.
Differences between PV Point (emergency output without a battery, up to 3 kW) and Full Backup (full backup with a battery and switch box) in the Fronius Primo, Symo and GEN24 Plus inverters, and what you need for each.
What to do when Solar.web shows that the inverter is disconnected (code 1030): check the Wi-Fi/LAN connection, reconfigure the Datamanager 2.0 or GEN24 access point, DHCP, DNS and ports.
How to connect the Fronius Smart Meter (TS 65A-3, TS 100A-1, IP) via Modbus RTU, configure it on the Primo/Symo and GEN24, and set the feed-in limit to 0 W for self-consumption without surplus.
