Solar Inverter Fault Codes

Fronius Inverter Fault Codes

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Fronius Inverter Fault Codes

Fronius Inverter Error Codes and Troubleshooting Guide

Published: October 15, 2025

If your Fronius inverter is showing a fault or warning code, this guide will help you understand what it means and what action to take.

Fronius inverters are a trusted brand used in residential, commercial, and industrial solar installations. They are generally very reliable, but like any electrical equipment, they can occasionally display error codes or warning messages.

This page explains the most common Fronius inverter errors, grouped by inverter model and STATE code range, with likely causes and recommended remedies.

If you are unsure what a code means, or your inverter is not generating power, contact Mr Solar for expert help.

Need Help With a Fronius Fault?

If your inverter is showing a persistent fault code, not generating as expected, or repeatedly shutting down, contact Mr Solar for diagnosis and repair support.

Call: Mr Solar 01603 394104 or 01493 289118
Contact us online: Here

Fronius IG Inverter Error Codes

STATE Codes 1xx

STATE codes beginning with 1xx are usually temporary and are caused by the electrical grid being outside the inverter’s permitted operating range.

Code Description Possible Causes Recommended Remedy
STATE 101 Grid voltage beyond permitted limits Mains voltage error; incorrect service menu settings; internal fault Check grid voltage and circuit breakers. Review service menu settings. If the issue continues, contact Mr Solar.
STATE 104 Mains frequency beyond permitted limits Mains frequency error; incorrect service menu settings; internal fault Check mains frequency and circuit breakers. Review service menu settings. If the issue continues, contact Mr Solar.
STATE 107 Synchronisation with the public mains supply not possible Mains not connected; incorrect service menu settings; internal fault Check mains connection and circuit breakers. Review service menu settings. If the issue continues, contact Mr Solar.
STATE 108 Islanding detected Islanding event; severe grid disturbances; internal fault Usually corrected automatically. If the problem persists, contact Mr Solar.

STATE Codes 2xx

STATE codes beginning with 2xx are messages from the inverter’s integrated grid monitoring device (ENS) and relate to public mains parameters.

Code Description Possible Causes Recommended Remedy
STATE 101 Grid voltage beyond permitted limits Mains voltage error; incorrect service menu settings; internal fault Check grid voltage and circuit breakers. Review service menu settings. If the issue continues, contact Mr Solar.
STATE 104 Mains frequency beyond permitted limits Mains frequency error; incorrect service menu settings; internal fault Check mains frequency and circuit breakers. Review service menu settings. If the issue continues, contact Mr Solar.
STATE 107 Synchronisation with the public mains supply not possible Mains not connected; incorrect service menu settings; internal fault Check mains connection and circuit breakers. Review service menu settings. If the issue continues, contact Mr Solar.
STATE 108 Islanding detected Islanding event; severe grid disturbances; internal fault Usually corrected automatically. If the problem persists, contact Mr Solar.

STATE Codes 3xx

STATE codes beginning with 3xx can occur during normal feed-in operation. These do not usually indicate damaged electronics and often clear automatically.

Code Description Possible Causes Recommended Remedy
STATE 301 Safety circuit detects a current peak on the mains supply Voltage drop on public mains; internal fault Usually corrected automatically. If persistent, contact Mr Solar.
STATE 302 Safety circuit detects a current peak on the PV generator side Voltage drop on public mains; internal fault Usually corrected automatically. If persistent, contact Mr Solar.
STATE 303 Heat sink temperature on the DC-AC board too high Blocked ventilation; high ambient temperature; insufficient spacing; internal fault Clear ventilation slots, improve cooling, increase inverter spacing. If persistent, contact Mr Solar.
STATE 304 Heat sink temperature on the DC-DC board too high Overheating Check cooling and ventilation.
STATE 305 Feed-in process not possible even though public mains parameters are within limits Internal fault Contact Mr Solar.
STATE 306 POWER LOW Intermediate circuit voltage below threshold Check solar panels and system performance. If persistent, contact Mr Solar.
STATE 307 DC LOW DC input voltage too low; internal fault Check PV voltage and panel performance. If persistent, contact Mr Solar.
STATE 308 Intermediate circuit voltage above maximum limit Public mains disturbances; internal fault Reinforce mains cable if required. If persistent, contact Mr Solar.

STATE Codes 4xx

STATE codes beginning with 4xx usually require the intervention of a qualified service engineer or Fronius service partner.

Code Description Recommended Remedy
STATE 401 Communication error between IG control and the DC-DC board Contact Mr Solar
STATE 402 Write access to internal memory failed Contact Mr Solar
STATE 403 Country setting memory incomplete Contact Mr Solar
STATE 404 Fault between control unit and ENS Check public mains, then contact Mr Solar if unresolved
STATE 405 Incorrect or outdated ENS microprocessor version recognised Contact Mr Solar
STATE 406 Temperature sensor on DC-AC board faulty or disconnected Contact Mr Solar
STATE 407 Temperature sensor on DC-DC board faulty or disconnected Contact Mr Solar
STATE 408 Unsymmetry on public mains detected Usually corrected automatically; contact Mr Solar if persistent
STATE 409 Supply of DC-AC board not available Contact Mr Solar
STATE 410 Service plug on DC-AC board incorrectly set Contact Mr Solar
STATE 412 Fixed voltage value set too high Contact Mr Solar
STATE 413 Open circuit voltage too high during transformer switching Contact Mr Solar
STATE 414 Memory array for inverter type faulty Automatic correction may occur; if persistent, contact Mr Solar
STATE 415 No ENS enabling signal despite release by IG control Contact Mr Solar
STATE 416 Communication error between IG control and power stack Automatic correction may occur; if persistent, contact Mr Solar
STATE 417 Hardware ID collision Contact Mr Solar
STATE 419 Duplicate power stack unique ID Contact Mr Solar
STATE 420 Incomplete number of power stacks detected Contact Mr Solar
STATE 421 Hardware ID sequence error Contact Mr Solar
STATE 425 Data exchange timeout with one or more power stacks Automatic correction may occur; if persistent, contact Mr Solar
STATE 431 All power stacks in boot mode Contact Mr Solar
STATE 432 Power stack management error Automatic correction may occur; if persistent, contact Mr Solar
STATE 433 Allocation error of dynamic addresses Contact Mr Solar
STATE 434 Ground fault detected Contact Mr Solar
STATE 435 Wrong EE-Prom configuration Contact Mr Solar
STATE 436 Error transmission faulty Contact Mr Solar
STATE 437 Power stack workaround active Contact Mr Solar
STATE 438 Error during state code transmission Automatic correction may occur; if persistent, contact Mr Solar
STATE 441 Power rack fan faulty Contact Mr Solar
STATE 442 Master for one phase could not be assigned Usually self-correcting; if persistent, contact Mr Solar
STATE 443 DC-DC energy transfer failure Usually self-correcting; if persistent, contact Mr Solar
STATE 444 AC monitoring self-test interrupted Press ESC, then resolve fault according to displayed code

STATE Codes 5xx

STATE codes beginning with 5xx usually do not stop feed-in operation. They often remain on the display until acknowledged.

Code Description Recommended Remedy
STATE 501 Heat sink temperature too high while on low output Clear ventilation slots; if persistent, contact Mr Solar
STATE 502 Isolation fault between DC+ or DC- and earth Check solar cables and generator
STATE 504 Error occurred while scanning LocalNet addresses Check inverter and component addresses
STATE 505 Internal memory for setup values incomplete Usually self-correcting; if persistent, contact Mr Solar
STATE 506 Internal memory for total values incomplete Contact Mr Solar if persistent
STATE 507 Internal memory for day/year values incomplete Contact Mr Solar if persistent
STATE 508 Internal memory for inverter number damaged Contact Mr Solar if persistent
STATE 509 No feed-in for 24 hours Check for snow, dirt, shading, or insufficient generation
STATE 510 Errors detected by LocalNet self-diagnostic system Usually self-correcting; if persistent, contact Mr Solar
STATE 511 Errors detected by LocalNet Sensor Card self-diagnostic system Contact Mr Solar if persistent
STATE 512 Too many power stacks detected Contact Mr Solar
STATE 513 Power stacks in boot mode Contact Mr Solar
STATE 514 Incomplete number of power stacks detected Contact Mr Solar
STATE 515 Power stacks notified STATE 406 / 407 / 409 / 410 Contact Mr Solar

Fronius Galvo Common Errors

STATE Codes 1xx

These codes are usually momentary and caused by the grid being outside permitted operating limits.

Code Description Remedy
STATE 102 AC voltage too high Check grid connections. If recurring, contact Mr Solar.
STATE 103 AC voltage too low Check grid connections. If recurring, contact Mr Solar.
STATE 105 AC frequency too high Check grid conditions. If recurring, contact Mr Solar.
STATE 106 AC frequency too low Check grid conditions. If recurring, contact Mr Solar.
STATE 107 AC grid outside permissible limits Check grid conditions. If recurring, contact Mr Solar.
STATE 108 Stand-alone operation detected Contact Mr Solar if recurring.

STATE Codes 3xx

These are operational status codes that often clear automatically.

Code Description Remedy
STATE 301 Overcurrent (AC) Usually self-correcting. If persistent, contact Mr Solar.
STATE 302 Safety circuit detects current peak on PV side Usually self-correcting. If persistent, contact Mr Solar.
STATE 303 Power stage over temperature Clear ventilation openings and heat sink. If recurring, contact Mr Solar.
STATE 304 Internal temperature too high Improve cooling and airflow.
STATE 306 LOW PV OUTPUT Normal in low sunlight. If seen in strong sunlight, contact Mr Solar.
STATE 307 LOW PV VOLTAGE Normal in low sunlight. If seen in strong sunlight, contact Mr Solar.
STATE 308 Intermediate circuit overvoltage Usually self-correcting. If persistent, contact Mr Solar.
STATE 309 DC input voltage too high Contact Mr Solar if persistent.

STATE Codes 4xx

These codes usually require service intervention.

Code Description Remedy
STATE 401 No communication with power stage set If persistent, contact Mr Solar
STATE 406 Power stage temperature sensor faulty Contact Mr Solar
STATE 407 Internal temperature sensor faulty Contact Mr Solar
STATE 408 DC feeding into grid detected Contact Mr Solar
STATE 412 Fixed voltage mode selected incorrectly Contact Mr Solar if persistent
STATE 415 Safety cut-out triggered Contact Mr Solar
STATE 416 Communication problem between power stage and control system If persistent, contact Mr Solar
STATE 425 No communication with power stage set Contact Mr Solar
STATE 445 Invalid limit value settings Update firmware, then contact Mr Solar if unresolved
STATE 452 Communication error between processors If persistent, contact Mr Solar
STATE 453 Short-term grid voltage error Monitor and contact Mr Solar if recurring
STATE 454 Short-term grid frequency error Monitor and contact Mr Solar if recurring
STATE 457 Grid relay sticking Contact Mr Solar
STATE 459 Error recording insulation test signal Contact Mr Solar
STATE 460 DSP reference voltage out of tolerance Contact Mr Solar
STATE 472 Solar panel ground fuse faulty Replace fuse; if recurring, contact Mr Solar
STATE 475 Solar panel insulation fault Contact Mr Solar if recurring
STATE 482 Startup incomplete Perform AC reset and complete startup

STATE Codes 5xx

These are warning-level codes and often do not stop generation.

Code Description Remedy
STATE 502 Insulation error on solar panels If recurring, contact Mr Solar
STATE 509 No energy fed into grid in past 24 hours Check operating conditions and other codes
STATE 516 Firmware fault Update firmware; if persistent, contact Mr Solar
STATE 517 Derating caused by high temperature Clean cooling paths and improve airflow
STATE 551 Solar panel ground fuse faulty Replace fuse; if recurring, contact Mr Solar
STATE 558 Functional incompatibility between PC boards Contact Mr Solar
STATE 560 Derating caused by over-frequency Usually automatic; if recurring, contact Mr Solar
STATE 567 Grid Voltage Dependent Power Reduction active Warning only; if recurring, contact Mr Solar
STATE 568 Incorrect input signal on multifunction current interface Check connected devices; if recurring, contact Mr Solar

STATE Codes 6xx

Code Description Remedy
STATE 668 Incorrect input signal on multifunction current interface Check connected devices. If recurring, contact Mr Solar.

STATE Codes 7xx

These codes relate to control systems, configuration, USB functions, firmware updates, and data recording.

Code Description Remedy
STATE 705 Conflict when setting inverter number Correct inverter number in setup menu
STATE 721 EEPROM reinitialised or faulty Acknowledge code; if persistent, contact Mr Solar
STATE 731 USB stick not supported Replace or reformat USB stick
STATE 732 Overcurrent on USB stick Check or replace USB stick
STATE 733 No USB stick connected Insert or check USB stick
STATE 734 Update file not recognised Check filename and update file
STATE 735 Update file incorrect or too old Use correct firmware file
STATE 736 Write/read error Check or replace USB stick
STATE 738 Log file cannot be saved Free space, remove write protection, or replace USB stick
STATE 743 Error during update process Repeat update and check USB stick
STATE 745 Update file corrupt Re-download firmware
STATE 751 Time lost Reset time and date
STATE 752 RTC communication error Contact Mr Solar if persistent
STATE 757 RTC hardware error Contact Mr Solar
STATE 758 RTC emergency mode Time may be inaccurate
STATE 766 Emergency power derating activated Contact Mr Solar if persistent

Fronius Primo Inverter Error Codes

STATE Codes 1xx

Code Description Remedy
STATE 102 AC voltage too high Check grid connections; if recurring, contact Mr Solar
STATE 103 AC voltage too low Check grid connections; if recurring, contact Mr Solar
STATE 105 AC frequency too high Check grid conditions
STATE 106 AC frequency too low Check grid conditions
STATE 107 AC grid outside permissible limits Check grid conditions
STATE 108 Stand-alone operation detected Contact Mr Solar if recurring
STATE 112 RCMU error Contact Mr Solar if recurring

STATE Codes 3xx

Code Description Remedy
STATE 301 Overcurrent (AC) Usually self-correcting; if persistent, contact Mr Solar
STATE 302 Overcurrent (DC) Usually self-correcting; if persistent, contact Mr Solar
STATE 303 Power stage over temperature Improve airflow and clear cooling paths
STATE 304 Internal temperature too high Improve ventilation
STATE 306 LOW PV OUTPUT Normal in low light; if occurring in full sun, contact Mr Solar
STATE 307 LOW PV VOLTAGE Normal in low light; if occurring in full sun, contact Mr Solar
STATE 308 Intermediate circuit overvoltage Usually self-correcting; if persistent, contact Mr Solar
STATE 309 DC input voltage MPPT 1 too high Contact Mr Solar if persistent
STATE 313 DC input voltage MPPT 2 too high Contact Mr Solar if persistent

STATE Codes 4xx

These usually require technical intervention. As a first step, shut the system down following the correct procedure, leave it off for a few minutes, then restart it.

Code Description Remedy
STATE 401 No communication with power stage set If persistent, contact Mr Solar
STATE 406 Power stage temperature sensor faulty Contact Mr Solar
STATE 407 Internal temperature sensor faulty Contact Mr Solar
STATE 408 DC feeding into grid detected Contact Mr Solar
STATE 412 Fixed voltage mode set incorrectly Contact Mr Solar
STATE 415 Safety cut-out triggered Contact Mr Solar
STATE 416 No communication between power stage and control system Contact Mr Solar if persistent
STATE 417 Hardware ID problem Contact Mr Solar
STATE 419 Unique ID conflict Contact Mr Solar
STATE 421 HID range error Contact Mr Solar
STATE 425 No communication with power stage set Contact Mr Solar
STATE 426–428 Possible hardware fault Contact Mr Solar
STATE 431 Software problem Perform AC reset, update firmware, contact Mr Solar if unresolved
STATE 436 Functional incompatibility Update firmware; contact Mr Solar if unresolved
STATE 437 Power stage set problem Contact Mr Solar
STATE 438 Functional incompatibility Contact Mr Solar
STATE 443 Intermediate circuit voltage too low or asymmetric Contact Mr Solar
STATE 445 Invalid limit value settings Update firmware; contact Mr Solar if unresolved
STATE 447 Insulation fault Contact Mr Solar
STATE 448 Neutral conductor not connected Contact Mr Solar
STATE 450 Guard cannot be found Contact Mr Solar
STATE 452 Memory error detected / communication error between processors Contact Mr Solar if persistent
STATE 453 Short-term grid voltage error Monitor and contact Mr Solar if recurring
STATE 454 Short-term grid frequency error Monitor and contact Mr Solar if recurring
STATE 456 Anti-islanding function not implemented correctly Contact Mr Solar
STATE 457 Grid relay sticking Contact Mr Solar
STATE 459 Error recording insulation test signal Contact Mr Solar
STATE 460 DSP reference voltage out of tolerance Contact Mr Solar
STATE 461 DSP data memory fault Contact Mr Solar
STATE 462 DC feed monitoring routine error Contact Mr Solar
STATE 463 Reversed AC polarity / AC connector inserted incorrectly Check installation and contact Mr Solar
STATE 474 RCMU sensor faulty Contact Mr Solar
STATE 475 Solar panel insulation fault Contact Mr Solar
STATE 476 Driver supply voltage too low Contact Mr Solar
STATE 480 / 481 Functional incompatibility Update firmware, then contact Mr Solar
STATE 482 Startup incomplete Perform AC reset and complete startup
STATE 483 Voltage UDC fixed on MPP2 out of limits Check MPP settings
STATE 485 CAN transmit buffer full Perform AC reset; if persistent, contact Mr Solar

STATE Codes 5xx

Code Description Remedy
STATE 502 Insulation error on solar panels Contact Mr Solar if recurring
STATE 509 No energy fed into grid in past 24 hours Check operating conditions and related codes
STATE 515 No communication with filter Contact Mr Solar if persistent
STATE 516 No communication with storage unit Check storage unit
STATE 517 Derating caused by high temperature Improve cooling and airflow
STATE 522 DC1 input voltage too low Check voltage and polarity on input 1
STATE 523 DC2 input voltage too low Check voltage, polarity, and MPP settings on input 2
STATE 558 Functional incompatibility Contact Mr Solar
STATE 560 Derating caused by over-frequency Usually automatic; if recurring, contact Mr Solar
STATE 566 Arc detector switched off No fault; confirm by pressing Enter
STATE 567 Grid Voltage Dependent Power Reduction active Warning only; if recurring, contact Mr Solar

STATE Codes 7xx

Code Description Remedy
STATE 705 Conflict when setting inverter number Correct inverter number in setup menu
STATE 721 EEPROM reinitialised or faulty Acknowledge; if persistent, contact Mr Solar
STATE 731–745 USB / firmware / update file related errors Check USB stick, update file, and firmware
STATE 751 Time lost Reset time and date
STATE 752 RTC communication error Contact Mr Solar if persistent
STATE 757 RTC hardware error Contact Mr Solar
STATE 758 RTC emergency mode Time may be inaccurate
STATE 766 Emergency power derating activated Contact Mr Solar if persistent

Fronius Symo Error Codes

STATE Codes 1xx

Code Description Remedy
STATE 102 AC voltage too high Check grid connections; if recurring, contact Mr Solar
STATE 103 AC voltage too low Check grid connections; if recurring, contact Mr Solar
STATE 105 AC frequency too high Check grid conditions
STATE 106 AC frequency too low Check grid conditions
STATE 107 AC grid outside permissible limits Check grid conditions
STATE 108 Stand-alone operation detected Contact Mr Solar if recurring
STATE 112 RCMU error Contact Mr Solar if recurring

STATE Codes 3xx

Code Description Remedy
STATE 301 Overcurrent (AC) Usually self-correcting; if persistent, contact Mr Solar
STATE 302 Overcurrent (DC) Usually self-correcting; if persistent, contact Mr Solar
STATE 303 DC module over temperature Improve airflow and clean cooling paths
STATE 304 AC module over temperature Improve airflow and clean cooling paths
STATE 305 No power being fed in despite closed relay Usually temporary; if recurring, contact Mr Solar
STATE 306 PV output too low Normal in low sunlight; if seen in strong sun, contact Mr Solar
STATE 307 LOW PV VOLTAGE Normal in low sunlight; if seen in strong sun, contact Mr Solar
STATE 308 Intermediate circuit voltage too high Usually self-correcting; if persistent, contact Mr Solar
STATE 309 DC input voltage MPPT 1 too high Contact Mr Solar
STATE 311 Polarity of DC strings reversed Check DC string polarity immediately
STATE 313 DC input voltage MPPT 2 too high Contact Mr Solar
STATE 314 Current sensor calibration timeout Usually self-correcting; if persistent, contact Mr Solar
STATE 315 AC current sensor error Contact Mr Solar
STATE 316 Interrupt Check fail Contact Mr Solar
STATE 325 Overtemperature in connection area Improve ventilation
STATE 326 Fan 1 error Contact Mr Solar
STATE 327 Fan 2 error Contact Mr Solar

STATE Codes 4xx

These codes usually require technical support.

Code Description Remedy
STATE 401 No communication with power stage set Contact Mr Solar if persistent
STATE 406 AC module temperature sensor faulty (L1) Contact Mr Solar
STATE 407 AC module temperature sensor faulty (L2) Contact Mr Solar
STATE 408 DC component measured in grid too high Contact Mr Solar
STATE 412 Fixed voltage mode set incorrectly Contact Mr Solar
STATE 415 Safety cut-out triggered Contact Mr Solar
STATE 416 No communication between power stage and control system Contact Mr Solar if persistent
STATE 417 Hardware ID problem Update firmware; if persistent, contact Mr Solar
STATE 419 Unique ID conflict Contact Mr Solar
STATE 420 No communication with Hybrid Manager Contact Mr Solar
STATE 421 HID range error Contact Mr Solar
STATE 425 No communication with power stage set Contact Mr Solar
STATE 426–428 Possible hardware fault Contact Mr Solar
STATE 431 Software problem Perform AC reset, update firmware, contact Mr Solar if unresolved
STATE 436 Functional incompatibility Update firmware; contact Mr Solar if unresolved
STATE 437 Power stage set problem Contact Mr Solar
STATE 438 Functional incompatibility Contact Mr Solar
STATE 443 Intermediate circuit voltage too low or asymmetric Contact Mr Solar
STATE 445 Compatibility or configuration error Update firmware; if persistent, contact Mr Solar
STATE 447 Insulation fault Contact Mr Solar
STATE 448 Neutral conductor not connected Contact Mr Solar
STATE 450 Guard cannot be found Contact Mr Solar
STATE 451 Memory error detected Contact Mr Solar if persistent
STATE 452 Communication error between processors Contact Mr Solar if persistent
STATE 453 Grid voltage and power stage set incompatible Contact Mr Solar
STATE 454 Grid frequency and power stage set incompatible Contact Mr Solar
STATE 456 Anti-islanding function no longer implemented correctly Contact Mr Solar
STATE 457 Grid relay sticking or neutral-ground voltage too high Check grounding; if persistent, contact Mr Solar
STATE 458 Error recording measuring signal Contact Mr Solar
STATE 459 Error recording signal for insulation test Contact Mr Solar
STATE 460 DSP reference voltage out of tolerance Contact Mr Solar
STATE 461 DSP data memory fault Contact Mr Solar
STATE 462 Error with DC feed monitoring Contact Mr Solar
STATE 463 Reversed AC polarity Check installation
STATE 474 RCMU sensor faulty Contact Mr Solar
STATE 475 Solar panel ground fault / insulation fault Contact Mr Solar
STATE 476 Driver supply voltage too low Contact Mr Solar
STATE 480 / 481 Functional incompatibility Update firmware; if persistent, contact Mr Solar
STATE 482 Setup interrupted after initial startup Perform AC reset and complete setup
STATE 483 Voltage UDC fixed on MPP2 out of limits Check MPP settings
STATE 485 CAN transmit buffer full Perform AC reset; if persistent, contact Mr Solar

STATE Codes 5xx

Code Description Remedy
STATE 502 Insulation error on solar panels Contact Mr Solar if recurring
STATE 509 No energy fed into grid in past 24 hours Check operating conditions and other active codes
STATE 515 No communication with filter Contact Mr Solar if persistent
STATE 516 No communication with storage unit Check storage system
STATE 517 Power derating caused by high temperature Improve cooling and airflow
STATE 518 Internal DSP malfunction Contact Mr Solar if recurring
STATE 519 No communication with storage unit Check storage system
STATE 520 No energy fed into grid by MPPT1 in past 24 hours Check MPPT1 performance
STATE 522 DC low string 1 Check PV voltage on string 1
STATE 523 DC low string 2 Check PV voltage on string 2
STATE 558 / 559 Functional incompatibility Update firmware; if persistent, contact Mr Solar
STATE 560 Derating caused by over-frequency Usually automatic; if recurring, contact Mr Solar
STATE 564 Functional incompatibility Update firmware; if persistent, contact Mr Solar
STATE 566 Arc detector switched off No fault; confirm by pressing Enter
STATE 567 Grid Voltage Dependent Power Reduction active Warning only; if recurring, contact Mr Solar

STATE Codes 6xx

Code Description Remedy
STATE 601 CAN bus full Update firmware; if persistent, contact Mr Solar
STATE 603 AC module temperature sensor faulty (L3) Contact Mr Solar
STATE 604 DC module temperature sensor faulty Contact Mr Solar
STATE 607 RCMU error Press Enter to reset. If recurring, inspect the full solar system
STATE 608 Functional incompatibility Update firmware; if persistent, contact Mr Solar

STATE Codes 7xx

These codes relate to processor status, USB functions, firmware updates, timekeeping, and storage communication.

Code Description Remedy
STATE 701–716 Internal processor status information If persistent, contact Mr Solar
STATE 721 EEPROM reinitialised Acknowledge; if persistent, contact Mr Solar
STATE 722–730 Processor status information If persistent, contact Mr Solar
STATE 731 USB flash drive not supported Replace or reformat USB flash drive
STATE 732 Overcurrent on USB stick Check USB device
STATE 733 No USB flash drive connected Insert or check USB flash drive
STATE 734 Update file not recognised Check update file name and format
STATE 735 Update file incorrect or too old Check correct firmware version
STATE 736 Write or read error Check or replace USB flash drive
STATE 737 File could not be opened Reinsert or replace USB flash drive
STATE 738 Log file cannot be saved Free space or remove write protection
STATE 740 File system error on USB flash drive Reformat to FAT12, FAT16, or FAT32
STATE 741 Error during logging Reinsert or replace USB flash drive
STATE 743 Error during update process Repeat update process
STATE 745 Update file corrupt Re-download update file
STATE 746 Error during update process Wait 2 minutes, then restart update
STATE 751 Time lost Reset inverter time and date
STATE 752 RTC communication error Contact Mr Solar if persistent
STATE 753 RTC emergency mode Time may be inaccurate
STATE 754–755 Processor status information If persistent, contact Mr Solar
STATE 757 RTC hardware error Contact Mr Solar
STATE 758 RTC emergency mode Reset time and date
STATE 760 Internal hardware error Contact Mr Solar
STATE 761–765 Internal processor status information Contact Mr Solar if persistent
STATE 766 Emergency power derating activated Contact Mr Solar if persistent
STATE 767 Internal processor status information Contact Mr Solar if persistent
STATE 768 Different power limitation in hardware modules Contact Mr Solar
STATE 772 Storage unit not available Check storage system
STATE 773 Invalid country setup Check configuration
STATE 775 PMC power stage set not available Press Enter to acknowledge; if persistent, contact Mr Solar
STATE 776 Invalid device type Contact Mr Solar
STATE 781–794 Internal processor status information Contact Mr Solar if persistent

Common Fronius Faults That Often Do Not Indicate a Serious Problem

Some Fronius codes are common and may be temporary:

  • STATE 102 / 103 / 105 / 106 / 107 – Grid voltage or frequency outside limits

  • STATE 306 / 307 – Low PV output or low PV voltage, often early morning or late evening

  • STATE 517 – Temperature-related power derating

  • STATE 567 – Grid Voltage Dependent Power Reduction active

These often clear automatically once grid conditions, sunlight levels, or inverter temperature return to normal.

When to Contact Mr Solar

You should contact Mr Solar if:

  • the same fault code keeps returning

  • your inverter is no longer generating electricity

  • you see an insulation fault, grid relay fault, or RCMU error

  • your inverter repeatedly shuts down

  • you have a 4xx, 6xx, or persistent 7xx STATE code

  • you are unsure how to safely reset or inspect the system

Fronius Inverter Repairs and Support

Mr Solar can help with:

  • Fronius inverter fault diagnosis
  • solar inverter repairs
  • inverter replacements and upgrades
  • solar PV maintenance
  • system performance checks
  • solar safety inspections

Call Mr Solar today: 0151 665 0560
Or contact us online: [Insert Contact Page Link]

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Fronius Inverter Error Codes and Troubleshooting Guide

If your Fronius inverter is showing a warning or fault code, this guide will help you understand what it means and what action to take.

Fronius inverters are widely used across domestic and commercial solar PV systems because they are efficient, dependable, and easy to monitor. Even so, like any solar inverter, they can occasionally display STATE codes that indicate a temporary warning, a grid-related issue, or a fault requiring technical attention.

At Mr Solar, we help homeowners and businesses diagnose and resolve Fronius inverter issues quickly and safely. Below, you’ll find the most common Fronius inverter error codes for the IG, Galvo, Primo and Symo ranges, along with likely causes and recommended next steps.

Need Help With a Fronius Fault?

If your inverter is repeatedly showing an error code, not generating properly, or has stopped producing power altogether, contact Mr Solar for expert support.

Call: 0151 665 0560
Contact us online: [Insert Contact Page URL]

On This Page

  • Fronius inverter error codes overview

  • Fronius IG error codes

  • Fronius Galvo common errors

  • Fronius Primo error codes

  • Fronius Symo error codes

  • Common Fronius faults that are often harmless

  • When to contact Mr Solar

  • Frequently asked questions

Understanding Fronius Inverter Error Codes

Fronius inverters use STATE codes to indicate different operating conditions. Some are temporary and clear on their own, while others point to a hardware issue, grid problem, insulation fault, or communication error.

In general:

  • 1xx codes usually relate to grid voltage or frequency problems

  • 3xx codes are often temporary operating conditions

  • 4xx codes usually indicate a fault that may require service support

  • 5xx codes are typically warnings that do not always stop generation

  • 6xx and 7xx codes can relate to communication, control systems, firmware, or hardware compatibility issues

Fronius IG Inverter Error Codes

Fronius IG STATE Codes 1xx

These codes are usually temporary and are caused by the electrical grid being outside the inverter’s permitted operating range.

Code Description Common Cause Recommended Action
STATE 101 Grid voltage beyond permitted limits Mains voltage error, incorrect settings, internal fault Check grid voltage and circuit breakers. If the issue continues, contact Mr Solar.
STATE 104 Mains frequency beyond permitted limits Frequency error, incorrect settings, internal fault Check mains frequency and breakers. If persistent, contact Mr Solar.
STATE 107 Synchronisation with public mains supply not possible Mains not connected, incorrect settings, internal fault Check mains connection and circuit breakers.
STATE 108 Islanding detected Grid disturbance or islanding event Usually clears automatically. If repeated, contact Mr Solar.

Fronius IG STATE Codes 2xx

These codes are messages from the integrated grid monitoring device and relate to public mains parameters.

Code Description Recommended Action
STATE 101 Grid voltage beyond permitted limits Check grid voltage and circuit breakers
STATE 104 Mains frequency beyond permitted limits Check mains frequency and circuit breakers
STATE 107 Synchronisation with public mains supply not possible Check mains power supply
STATE 108 Islanding detected Monitor system and contact Mr Solar if persistent

Fronius IG STATE Codes 3xx

These can occur during grid feed-in operation and do not normally indicate permanent damage.

Code Description Recommended Action
STATE 301 Current peak detected on mains supply Usually self-correcting
STATE 302 Current peak detected on PV generator side Usually self-correcting
STATE 303 Heat sink temperature on DC-AC board too high Clear ventilation slots and improve airflow
STATE 304 Heat sink temperature on DC-DC board too high Check cooling and airflow
STATE 305 Feed-in process not possible despite acceptable mains parameters Contact Mr Solar
STATE 306 POWER LOW Check panels and output levels
STATE 307 DC LOW Check DC input voltage and panel performance
STATE 308 Intermediate circuit voltage too high Check for mains disturbances

Fronius IG STATE Codes 4xx

These codes usually require technical support.

Common examples include:

  • STATE 401 – Communication error between control and DC-DC board

  • STATE 404 – Fault between control unit and ENS

  • STATE 406 / 407 – Temperature sensor fault

  • STATE 409 / 410 – DC-AC board supply or setup issue

  • STATE 434 – Ground fault detected

  • STATE 441 – Power rack fan faulty

  • STATE 443 – DC-DC energy transfer failure

If your Fronius IG inverter is displaying a 4xx code continuously, contact Mr Solar.

Fronius IG STATE Codes 5xx

These are generally warning messages and may not stop generation.

Common examples include:

  • STATE 501 – Heat sink temperature too high

  • STATE 502 – Isolation fault between DC and earth

  • STATE 504 – LocalNet address scanning error

  • STATE 509 – No feed-in operation for 24 hours

  • STATE 510–515 – LocalNet, sensor card, or power stack related warnings

Fronius Galvo Error Codes

Fronius Galvo STATE Codes 1xx

These codes usually appear momentarily and are linked to grid conditions.

Code Description Recommended Action
STATE 102 AC voltage too high Check grid connections
STATE 103 AC voltage too low Check grid connections
STATE 105 AC frequency too high Monitor mains supply
STATE 106 AC frequency too low Monitor mains supply
STATE 107 AC grid outside permissible limits Check supply conditions
STATE 108 Stand-alone operation detected Contact Mr Solar if repeated

Fronius Galvo STATE Codes 3xx

These are typically temporary operational warnings.

Code Description Recommended Action
STATE 301 Overcurrent (AC) Usually self-correcting
STATE 302 Current peak on PV generator side Usually self-correcting
STATE 303 Power stage over temperature Clear cooling air paths
STATE 304 Internal temperature too high Improve ventilation
STATE 306 LOW PV OUTPUT Normal in low light, investigate if in full sun
STATE 307 LOW PV VOLTAGE Normal in low light, investigate if in full sun
STATE 308 Intermediate circuit overvoltage Usually self-correcting
STATE 309 DC input voltage too high Contact Mr Solar if persistent

Fronius Galvo STATE Codes 4xx to 7xx

These can indicate communication problems, firmware issues, sensor faults, insulation faults, USB update errors, or internal hardware problems.

Important examples include:

  • STATE 401 – No communication with power stage

  • STATE 445 – Invalid limit value settings

  • STATE 457 – Grid relay sticking

  • STATE 472 / 475 – Solar panel ground or insulation fault

  • STATE 482 – Startup incomplete

  • STATE 516 – Firmware fault

  • STATE 567 – Grid Voltage Dependent Power Reduction active

  • STATE 705 / 721 / 731–745 / 751–758 – Setup, USB, firmware, or clock-related errors

Fronius Primo Error Codes

Fronius Primo STATE Codes 1xx

These usually relate to grid conditions.

Code Description Recommended Action
STATE 102 AC voltage too high Check grid connections
STATE 103 AC voltage too low Check grid connections
STATE 105 AC frequency too high Monitor supply
STATE 106 AC frequency too low Monitor supply
STATE 107 AC grid outside permissible limits Check mains conditions
STATE 108 Stand-alone operation detected Contact Mr Solar if repeated
STATE 112 RCMU error Contact Mr Solar if persistent

Fronius Primo STATE Codes 3xx

These are often temporary and do not always indicate a serious fault.

Code Description Recommended Action
STATE 301 Overcurrent (AC) Usually clears automatically
STATE 302 Overcurrent (DC) Usually clears automatically
STATE 303 Power stage over temperature Improve airflow and ventilation
STATE 304 Internal temperature too high Improve cooling
STATE 306 LOW PV OUTPUT Often normal in early morning or evening
STATE 307 LOW PV VOLTAGE Often normal in low sunlight
STATE 308 Intermediate circuit overvoltage Usually temporary
STATE 309 DC input voltage MPPT 1 too high Investigate string voltage
STATE 313 DC input voltage MPPT 2 too high Investigate string voltage

Fronius Primo STATE Codes 4xx to 7xx

These codes can indicate hardware, communication, firmware, insulation, polarity, or startup issues.

Important examples include:

  • STATE 401 – No communication with power stage

  • STATE 417 / 419 / 421 – Hardware ID or unique ID issue

  • STATE 431 – Software problem

  • STATE 443 – Intermediate circuit voltage too low or asymmetric

  • STATE 447 / 475 – Insulation fault

  • STATE 463 – Reversed AC polarity

  • STATE 482 – Startup incomplete

  • STATE 517 – Derating caused by high temperature

  • STATE 522 / 523 – DC input voltage too low

  • STATE 566 – Arc detector switched off

  • STATE 567 – Grid Voltage Dependent Power Reduction active

Fronius Symo Error Codes

Fronius Symo STATE Codes 1xx

These codes are commonly caused by temporary grid conditions.

Code Description Recommended Action
STATE 102 AC voltage too high Check grid connections
STATE 103 AC voltage too low Check grid connections
STATE 105 AC frequency too high Monitor supply
STATE 106 AC frequency too low Monitor supply
STATE 107 AC grid outside permissible limits Check mains conditions
STATE 108 Stand-alone operation detected Contact Mr Solar if repeated
STATE 112 RCMU error Contact Mr Solar if persistent

Fronius Symo STATE Codes 3xx

These are often temporary operating messages.

Code Description Recommended Action
STATE 301 Overcurrent (AC) Usually clears automatically
STATE 302 Overcurrent (DC) Usually clears automatically
STATE 303 DC module over temperature Improve ventilation
STATE 304 AC module over temperature Improve ventilation
STATE 305 No power being fed in despite closed relay Monitor and investigate if repeated
STATE 306 PV output too low Often normal in low sunlight
STATE 307 LOW PV VOLTAGE Often normal in low sunlight
STATE 308 Intermediate circuit voltage too high Usually temporary
STATE 309 DC input voltage MPPT 1 too high Investigate string voltage
STATE 311 Polarity of DC strings reversed Check DC wiring urgently
STATE 313 DC input voltage MPPT 2 too high Investigate string voltage
STATE 325 Overtemperature in connection area Improve cooling
STATE 326 Fan 1 error Contact Mr Solar
STATE 327 Fan 2 error Contact Mr Solar

Fronius Symo STATE Codes 4xx to 7xx

These can relate to sensor faults, communication problems, incompatibility, firmware issues, grounding issues, and control system errors.

Important examples include:

  • STATE 401 – No communication with power stage

  • STATE 420 – No communication with Hybrid Manager

  • STATE 431 – Software problem

  • STATE 445 – Compatibility or configuration error

  • STATE 457 – Grid relay sticking or neutral-ground voltage too high

  • STATE 475 – Solar panel ground or insulation fault

  • STATE 601 / 603 / 604 / 607 / 608 – Service-level error codes

  • STATE 731–746 – USB or firmware update errors

  • STATE 751–760 – Real-time clock or internal hardware errors

  • STATE 772 / 773 / 775 / 776 – Storage, country setup, or device type issues

Common Fronius Inverter Faults That Are Often Not Serious

Some Fronius inverter messages are common and may clear automatically without repair.

These include:

  • STATE 102 / 103 / 105 / 106 / 107 – Grid voltage or frequency outside limits

  • STATE 306 / 307 – Low PV output or voltage in low sunlight

  • STATE 517 – Temperature-related derating

  • STATE 560 – Over-frequency derating

  • STATE 567 – Grid Voltage Dependent Power Reduction active

These are often linked to weather conditions, time of day, grid supply fluctuations, or temporary temperature rise.

When to Contact Mr Solar

You should get in touch with Mr Solar if:

  • the same Fronius error code keeps returning

  • your inverter has stopped generating electricity

  • your inverter is showing a 4xx, 6xx, or persistent 7xx code

  • you see an insulation fault, relay fault, grounding fault, or RCMU warning

  • your inverter repeatedly shuts down or restarts

  • you are unsure how to safely reset the system

Fronius Inverter Repairs, Diagnostics and Support

At Mr Solar, we provide expert support for Fronius inverter faults and solar PV performance issues.

Our services include:

  • Fronius inverter fault diagnosis

  • solar inverter repairs

  • inverter replacement and upgrade advice

  • solar PV maintenance

  • performance testing

  • electrical safety checks

  • system inspections for homeowners and businesses

Call Mr Solar: 0151 665 0560
Contact us online: [Insert Contact Page URL]

Frequently Asked Questions

What does a Fronius STATE code mean?

A Fronius STATE code is a diagnostic message shown by the inverter to identify a warning, operating condition, or fault. Some codes are temporary, while others require inspection or repair.

Which Fronius error codes are most common?

Common Fronius codes include 102, 103, 107, 306, 307, 517, and 567. These are often linked to grid conditions, low sunlight, or inverter temperature.

Is Fronius STATE 306 a fault?

Not always. STATE 306 usually means low PV output and is common during early morning, late evening, or very poor weather. If it appears during strong sunlight, it may need investigation.

Is Fronius STATE 567 serious?

STATE 567 usually means the inverter is reducing output because grid voltage is high. It is often a warning rather than a fault, but if it happens regularly, your system may need checking.

What should I do if my Fronius inverter stops generating?

Check whether the inverter is showing a STATE code, inspect for obvious issues such as tripped breakers, and review whether the problem may be due to low sunlight or grid conditions. If generation does not return, contact Mr Solar.

Can I reset a Fronius inverter myself?

In some cases, an AC reset may help clear a temporary fault. However, if the inverter continues showing errors, or if you suspect a wiring, insulation, or hardware issue, you should contact a qualified solar engineer.

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