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Fault code index · Fronius inverter all models

Fronius Fault Code Index

Every Fronius fault code and state code — what it means, the most likely cause, and what to do. Find your code in the index below or use the category sections to browse by system area.

Fronius Primo, Symo, Gen24 and GEN24 Plus Sourced from Fronius technical documentation State codes and error codes explained

Fronius Fault Code Index

Every Fronius fault code and state code — what it means, the most likely cause, and what to do. Find your code in the index below or use the category sections to browse by system area.
  • Fronius Primo, Symo, Gen24 and GEN24 Plus
  • Sourced from Fronius technical documentation
  • State codes and error codes explained
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5.0
13 Trustpilot reviews
Trustpilot Google

I have a GivEnergy system consisting of two batteries, two inverters and a controlling EMS (Energy Management System) which has not worked since Nov 2025. After six months I discovered Solar Tech Support, reached out to them and Ron phoned me back – how often do you get that service? Could not be more helpful – worked directly with me over the phone, outside what I would call normal working hours. Lucid explanations and we were able to discuss the issues and history using camera and email history. As this was a very rare setup, Ron was able to access an EMS expert in the field to confirm the solution. One sunny day in, I am now only paying for standing charge and a few pence for spikes in grid consumption while battery catches up with house demand.

Ian · May 2026 Trustpilot

When my GivEnergy system had an issue, I was completely left without support and had honestly lost all hope. Thankfully, I searched online and found Ron, which completely turned things around. After sending him a message, he responded incredibly fast and called me to assure me that he would get the problem fixed. I really admire his dedicated, supportive nature and his determination to find a solution. With this kind of outstanding attitude and customer service, he has absolutely secured a future customer in me.

Sree · May 2026 Trustpilot

Ron want out of is way to help, nothing was to much. He was very thorough in what he did Very knowledgeable I would highly recommend Ron and his company He did a fantastic job for me. if you have any problems, he'll do his best to help you out and resolve your problem. I wouldn't hesitate to recommend them

Dennis Brown · May 2026 Trustpilot

Ron took me through a diagnostic to confirm my GivEnergy Inverter had a fault. A common one as it turns out with the AC Inverter. As GivEnergy is defunct there is no immediate fix, aside from sourcing 2nd hand replacement. It may be that a fix becomes available over the summer which would make a lot of GivEnergy customers happy (Again)

Tony Deacon · May 2026 Trustpilot

Contacted Ron with a problem and he sorted it out quickly with no problems at all. Very knowledgeable on anything solar/ batteries. I would recommend him to anyone

Phill · May 2026 Trustpilot

I've spoken to Ron a couple of times with issues with my Givenergy installation. Such a friendly knowledge guy very highly recommended. Thank you very much for resolving my issues

michael fairhurst · May 2026 Trustpilot

Contacted Solar Tech Support in desperation. After explaining the issues I had with my system a diagnosis was made and a solution proposed. Fantastic service, even contacted a manufacturer to arrange replacement parts for me. Great communications, explained all they were doing and what I had to do, clearly and precisly. Followed up to confirm all was ok. Excellent service.

Mr Machin · May 2026 Trustpilot

After GivEnergy went into liquidation, just my luck, my battery started playing up (internal board crashed). Contacted my installer - not interested! Found Solar tech support on a Google search. Sooo glad I found this company! Ron is extremely helpful and has plenty of experience. He soon confirmed what the fault was, and helped me to get my system up and running again. Now moved my GivEnergy account to Solar tech support, and will definitely use again if I have more issues. Unusual to find such a helpful company in these times, no morons reading scripts, just direct contact with the engineer.

Keith Ballard · Apr 2026 Trustpilot

Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.

Hugh Speirs · Apr 2026 Trustpilot

Ron is a super star. Two months ago my GivEnergy battery failed a firmware upgrade leaving it a brick. My installer couldn't/wouldn't fix it. GivEnergy couldn't/wouldn't fix it. Then they went into administration and all hope was lost. A flurry of emails later and Ron had diagnosed the fault (failed USB flash drive, something I'd suspected) and talked me through resolving it. Two months of nothing resolved in about 3 hours. It's great to work with someone who pays attention to the details, knows that they're doing (not just following a script) and gets stuff sorted without a fuss or up-charging.

Christopher · Apr 2026 Trustpilot

I can add to the list of customers who had already 'given up' on GivEnergy due to their appalling customer service, and that was before they went into administration (their Trustpilot reviews don't lie!). So you can imagine my desperation when, having changed my ISP and my Inverter, predictably, proving to be the only device that didn't connect automatically to my new network, I found zero prospect of any customer support with GivEnergy having called in the administrators just five days earlier! The salvation came from Solar Tech Support. My IT advisor stumbled across their web site and some very helpful tips for beleaguered GivEnergy customers, as well as an offer to provide direct assistance. Nothing ventured, I decided to drop them an E-Mail, with very low expectations based on my experience of GivEnergy customer support. Within an hour Ron had responded with some pin point advice, and after a few exchanges of E-Mails he had nailed the problem, enabling the combined efforts of my IT advisor and solar installer to resolve it and reconnect my Inverter. Thank you Solar Tech Support, and Ron in particular, for coming to the aid of a deserted and despondent GivEnergy customer. Expert, razor sharp advice and first class customer service, even though I wasn't officially a customer.

customer · Apr 2026 Trustpilot

This company are a rare gem, I had a very unusual problem following a failed firmware upgrade on my GivEnergy kit. I then found out GivEnergy were in administration and had dismissed all their support staff! None of the usual fixes to try and restore my inverter comms would work, and I looked everywhere, forums, GivEnergy youtube support videos - even AI couldn't figure it out. My installer was talking about huge sums for system replacements, and being vague / evasive about if they'd even install replacement GivEnergy inverter. Enter Solar Tech Support, reassuring and knowledgeable from the very start, I've learnt loads about my solar system though the friendly chat while my engineer worked as he diagnosed the problem and figured out a fix procedure that I've not found anywhere else - amazing . If you need solar system repairs - especially if you like me have been left high and dry by GivEnergy, I cannot recommend this company enough. Give them a call.

Andy Thomas · Apr 2026 Trustpilot

I sent a message on their website regarding a problem I have on my Givenergy system. Although not supplied by Ronald, I thought it was worth an email. Within the hour on a Saturday, he phoned and we discussed the problem. He logged in remotely and gave excellent advice. I'm too far away for his on-site help but he did diagnose the problem and was happy also to chat through my thoughts about an upcoming solar/battery install I'm planning. Great bloke.... if only he was nearer!

Philip · Apr 2026 Trustpilot

I have a GivEnergy system consisting of two batteries, two inverters and a controlling EMS (Energy Management System) which has not worked since Nov 2025. After six months I discovered Solar Tech Support, reached out to them and Ron phoned me back – how often do you get that service? Could not be more helpful – worked directly with me over the phone, outside what I would call normal working hours. Lucid explanations and we were able to discuss the issues and history using camera and email history. As this was a very rare setup, Ron was able to access an EMS expert in the field to confirm the solution. One sunny day in, I am now only paying for standing charge and a few pence for spikes in grid consumption while battery catches up with house demand.

Ian · May 2026 Trustpilot

When my GivEnergy system had an issue, I was completely left without support and had honestly lost all hope. Thankfully, I searched online and found Ron, which completely turned things around. After sending him a message, he responded incredibly fast and called me to assure me that he would get the problem fixed. I really admire his dedicated, supportive nature and his determination to find a solution. With this kind of outstanding attitude and customer service, he has absolutely secured a future customer in me.

Sree · May 2026 Trustpilot

Ron want out of is way to help, nothing was to much. He was very thorough in what he did Very knowledgeable I would highly recommend Ron and his company He did a fantastic job for me. if you have any problems, he'll do his best to help you out and resolve your problem. I wouldn't hesitate to recommend them

Dennis Brown · May 2026 Trustpilot

Ron took me through a diagnostic to confirm my GivEnergy Inverter had a fault. A common one as it turns out with the AC Inverter. As GivEnergy is defunct there is no immediate fix, aside from sourcing 2nd hand replacement. It may be that a fix becomes available over the summer which would make a lot of GivEnergy customers happy (Again)

Tony Deacon · May 2026 Trustpilot

Contacted Ron with a problem and he sorted it out quickly with no problems at all. Very knowledgeable on anything solar/ batteries. I would recommend him to anyone

Phill · May 2026 Trustpilot

I've spoken to Ron a couple of times with issues with my Givenergy installation. Such a friendly knowledge guy very highly recommended. Thank you very much for resolving my issues

michael fairhurst · May 2026 Trustpilot

Contacted Solar Tech Support in desperation. After explaining the issues I had with my system a diagnosis was made and a solution proposed. Fantastic service, even contacted a manufacturer to arrange replacement parts for me. Great communications, explained all they were doing and what I had to do, clearly and precisly. Followed up to confirm all was ok. Excellent service.

Mr Machin · May 2026 Trustpilot

After GivEnergy went into liquidation, just my luck, my battery started playing up (internal board crashed). Contacted my installer - not interested! Found Solar tech support on a Google search. Sooo glad I found this company! Ron is extremely helpful and has plenty of experience. He soon confirmed what the fault was, and helped me to get my system up and running again. Now moved my GivEnergy account to Solar tech support, and will definitely use again if I have more issues. Unusual to find such a helpful company in these times, no morons reading scripts, just direct contact with the engineer.

Keith Ballard · Apr 2026 Trustpilot

Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.

Hugh Speirs · Apr 2026 Trustpilot

Ron is a super star. Two months ago my GivEnergy battery failed a firmware upgrade leaving it a brick. My installer couldn't/wouldn't fix it. GivEnergy couldn't/wouldn't fix it. Then they went into administration and all hope was lost. A flurry of emails later and Ron had diagnosed the fault (failed USB flash drive, something I'd suspected) and talked me through resolving it. Two months of nothing resolved in about 3 hours. It's great to work with someone who pays attention to the details, knows that they're doing (not just following a script) and gets stuff sorted without a fuss or up-charging.

Christopher · Apr 2026 Trustpilot

I can add to the list of customers who had already 'given up' on GivEnergy due to their appalling customer service, and that was before they went into administration (their Trustpilot reviews don't lie!). So you can imagine my desperation when, having changed my ISP and my Inverter, predictably, proving to be the only device that didn't connect automatically to my new network, I found zero prospect of any customer support with GivEnergy having called in the administrators just five days earlier! The salvation came from Solar Tech Support. My IT advisor stumbled across their web site and some very helpful tips for beleaguered GivEnergy customers, as well as an offer to provide direct assistance. Nothing ventured, I decided to drop them an E-Mail, with very low expectations based on my experience of GivEnergy customer support. Within an hour Ron had responded with some pin point advice, and after a few exchanges of E-Mails he had nailed the problem, enabling the combined efforts of my IT advisor and solar installer to resolve it and reconnect my Inverter. Thank you Solar Tech Support, and Ron in particular, for coming to the aid of a deserted and despondent GivEnergy customer. Expert, razor sharp advice and first class customer service, even though I wasn't officially a customer.

customer · Apr 2026 Trustpilot

This company are a rare gem, I had a very unusual problem following a failed firmware upgrade on my GivEnergy kit. I then found out GivEnergy were in administration and had dismissed all their support staff! None of the usual fixes to try and restore my inverter comms would work, and I looked everywhere, forums, GivEnergy youtube support videos - even AI couldn't figure it out. My installer was talking about huge sums for system replacements, and being vague / evasive about if they'd even install replacement GivEnergy inverter. Enter Solar Tech Support, reassuring and knowledgeable from the very start, I've learnt loads about my solar system though the friendly chat while my engineer worked as he diagnosed the problem and figured out a fix procedure that I've not found anywhere else - amazing . If you need solar system repairs - especially if you like me have been left high and dry by GivEnergy, I cannot recommend this company enough. Give them a call.

Andy Thomas · Apr 2026 Trustpilot

I sent a message on their website regarding a problem I have on my Givenergy system. Although not supplied by Ronald, I thought it was worth an email. Within the hour on a Saturday, he phoned and we discussed the problem. He logged in remotely and gave excellent advice. I'm too far away for his on-site help but he did diagnose the problem and was happy also to chat through my thoughts about an upcoming solar/battery install I'm planning. Great bloke.... if only he was nearer!

Philip · Apr 2026 Trustpilot
How to find your fault code. Fronius codes appear on the LED status lights on the inverter front panel. For detailed information, log into Fronius Solar.web → My Systems → [Device] → Events. The event log shows code numbers (State 240, Error 301, etc.) with timestamps and descriptions. Note the exact code number including the prefix — this indicates the code type and severity.
State codes

State codes indicate normal operating conditions, temporary restrictions, or routine maintenance — not faults. The inverter continues to operate normally with these state codes active.

State 240 Calibration active
Inverter is performing automatic calibration — a routine part of normal startup. No power will be generated during this brief period. This is normal behaviour and clears automatically. Usually lasts only a few seconds.
State 307 Active power limit engaged
Fronius is limiting output power as configured — export limit (power limitation due to grid requirements) is active. The inverter is generating but power is being capped. Check your Power Limitation settings in Solar.web to confirm the intended limit value.
State 406 Waiting for grid voltage
Inverter has disconnected from the grid due to an undervoltage or frequency event and is now waiting to reconnect. Typical reconnection delay is 5 minutes. No power is being generated during this hold period. Grid voltage and frequency must return within normal limits before the inverter resumes operation.
Grid & AC faults

Fault codes generated in response to AC grid voltage or frequency being outside safe operating limits. These cause the inverter to immediately disconnect from the grid.

Error 301 ⚠ Grid overvoltage
AC grid voltage has exceeded the upper safety limit (typically above 253V). Inverter has disconnected. This is usually a temporary grid disturbance. Monitor the event log — if the fault is persistent, contact your DNO about grid quality issues in your area.
Error 302 Grid undervoltage
AC grid voltage has dropped below the lower safety limit (typically below 216V). Inverter has disconnected. This often occurs during high-load periods on the local network. Wait for grid voltage to recover — the inverter will reconnect automatically.
Error 303 Grid overfrequency
Grid frequency has exceeded the upper safety limit (above 50.2Hz). Inverter disconnected. Frequency disturbances are usually caused by grid events affecting many users — check your local grid status. The inverter will reconnect when frequency normalizes.
Error 304 Grid underfrequency
Grid frequency has dropped below the lower safety limit (below 47.5Hz). Inverter disconnected. This indicates a significant grid disturbance — wait for frequency to recover. The inverter will reconnect automatically once frequency returns to normal range.
Error 306 ⚠ No mains connection
Grid power has been lost completely — AC supply is missing. Check circuit breakers at the consumer unit on the solar output circuit. Check the AC isolator below the inverter is switched ON. Verify the AC terminal connections are tight and not corroded.
DC & Insulation faults

Fault codes related to DC string voltage, insulation resistance, and ground faults. These faults typically prevent the inverter from starting or cause an immediate trip if detected during operation.

Error 401 High string current
DC string current is exceeding the inverter's safe input limit. Typically caused by incorrect panel array configuration — panels may be wired with too many in parallel. Check panel string sizing against Fronius documentation for your inverter model.
Error 402 String overvoltage
DC string voltage is exceeding the maximum input voltage (Voc) for this inverter. Check panel array configuration — may have too many panels in series. Do not touch DC cabling. Contact an engineer to review the string design.
Error 403 No DC power
DC input voltage is below the minimum start-up threshold. Check the DC string isolator (the breaker on the positive DC cable) is switched ON. Verify all MC4 connectors between panels and inverter are fully seated and locked. Check for panel shading or cloud cover reducing panel output.
Error 404 ⚠ Isolation fault — URGENT
Leakage current has been detected between the DC string and earth — a ground fault. This is a critical safety issue. Isolate the system immediately at the consumer unit. Do not touch any DC cabling. Check for water ingress at MC4 connectors, damaged insulation on string cables, or a faulty panel junction box. Contact a qualified engineer before any restart.
Error 405 ⚠ Arc fault detected — URGENT
A DC arc has been detected in the PV string — this is a fire safety hazard. Isolate the system at the consumer unit immediately. Do not touch any DC cabling or attempt to restart the system. Contact a qualified engineer to inspect string cabling and connectors for damage or loose connections.
Internal & thermal faults

Fault codes originating from inside the inverter — processor communication failures, cooling fan issues, and temperature protection events.

Error 501 DSP communication fault
Internal processor communication fault — the two processing units inside the inverter have lost synchronization. Perform a full power cycle (AC isolator off, wait 60 seconds, back on). If the fault persists, the control board may require a firmware reflash or replacement — contact Fronius support or a qualified engineer.
Error 502 Fan failure
Cooling fan is not operating. The inverter will derate (reduce power output) or shut down to protect internal components from overheating. Check for any visible debris or blockage around the inverter cooling vents. Ensure 20cm minimum clearance on all sides. If fan does not resume operation after restart, the fan motor may have failed and requires replacement.
Error 503 Overtemperature
Internal heatsink temperature has reached the thermal shutdown threshold. Check ventilation — ensure minimum 20cm clearance on all sides, no direct sunlight exposure, and no heat sources nearby. Clear any dust from cooling vents using compressed air. If ambient temperature is normal and clearances are adequate, the internal temperature sensor may be faulty.
Frequently asked questions
How often should I expect to see state codes on my Fronius?
State 240 (calibration) typically appears once monthly or after firmware updates — this is normal. State 307 (power limit) appears whenever your export limit is active. State 406 (waiting for grid) only appears after grid disturbances. None of these indicate a problem with your system.
Why does my Fronius show Error 301 even though my grid voltage seems normal?
Grid voltage varies constantly — it may be at normal levels during off-peak times but spike above 253V during peak generation periods, especially with many solar systems exporting power. Monitor how often Error 301 appears in your event log. If it's frequent, contact your DNO to investigate grid quality in your area.
Can I read Fronius fault codes without logging into Solar.web?
Yes — many faults show as LED codes on the inverter's front panel. However, for complete diagnostic information including timestamps and detailed descriptions, you'll need to log into Fronius Solar.web → My Systems → Events. This index will help you interpret both the LED codes and the event log entries.

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