Fronius Inverter Repair and Fault Codes
A State code on the display, no feed-in for a day, or an inverter that cuts out on hot afternoons? We diagnose and repair Fronius inverters from any installer, across England, Wales and Scotland.
Repairs you can rely on
- MCS registered
- NAPIT registered
- TrustMark approved
- Fully insured
- Any installer’s system
- In-house engineers — no subcontractors
Call us on 0800 156 0191
Monday to Friday, 9:00am–5:00pm
Is this what you’re seeing?
A State code on the inverter’s display
State 509: no energy fed into the grid for the past 24 hours
The inverter stops and restarts on hot, sunny days
A code that shows in good sunlight, not just at dawn and dusk
The display is blank, even in daylight
Solar.web shows the inverter offline or a service message
The solar breaker in the consumer unit keeps tripping
Write down the State number, or take a photo of the display.
Call 0800 156 0191 or use the fault finder further down this page. If the solar breaker keeps tripping, leave the system switched off until an engineer has looked at it.
Common Fronius faults
Fronius inverters report problems as numbered State codes on the display, and as service messages in Fronius Solar.web. Some codes clear themselves, some are normal at certain times of day, and some need a Fronius-trained engineer. We install solar and battery systems too, so we know how these faults show up in real homes.
Overheating
State 303 means part of the inverter has got too hot, so it stops feeding in until it cools down. Inverters in lofts, garages and cupboards with little airflow are the most likely to overheat. Fronius advises keeping the cooling vents clear. If the code keeps coming back, the ventilation and the inverter need looking at.
Overcurrent
State 301 and State 302 are overcurrent faults, on the AC side and the DC side. The inverter pauses briefly and restarts on its own. An occasional one isn’t a worry, but Fronius says a code that shows all the time needs a Fronius-trained service engineer.
Low panel power or voltage
State 306 and State 307 mean the panels aren’t producing enough power or voltage to feed the grid. Fronius notes these are normal early in the morning and in the evening. In good sunlight they point to a problem on the panel side, such as a failed string, a tripped isolator or a damaged connector.
No feed-in for 24 hours
State 509 is the inverter telling you it hasn’t exported anything for a whole day. Snow on the panels can cause it. If there’s no obvious reason, look at the display for other State codes, because 509 is usually a sign of another fault.
Repair or replace?
We always diagnose first. Many Fronius faults come down to ventilation or a problem on the panel side, and can be put right without a new inverter. If replacement is the better option, we explain why and give you a clear written quote before any work starts. Read more about inverter repair and replacement, or how we find faults across the whole system.
Fronius error codes and what they mean
The codes below come from Fronius’s operating instructions for the Symo, Primo and Galvo inverters. Fronius GEN24 inverters use a different, four-digit numbering, so these meanings don’t apply to them, and older Fronius IG Plus inverters aren’t covered here.
| Code | What it means | What to do |
|---|---|---|
| State 301 | Overcurrent on the AC side; feed-in pauses briefly | Wait: it restarts on its own. If it shows all the time, call us. |
| State 302 | Overcurrent on the DC (panel) side | Wait: it restarts on its own. If it shows all the time, call us. |
| State 303 | Overheating: part of the inverter is too hot | Check nothing is blocking the vents or the airflow around the inverter. If it keeps coming back, call us. |
| State 306 | Panel power too low to feed the grid | Normal at dawn and dusk. If it shows in good sunlight, call us. |
| State 307 | Panel (DC) voltage too low to feed the grid | Normal at dawn and dusk. If it shows in good sunlight, call us. |
| State 509 | No energy fed into the grid in the past 24 hours | Acknowledge the code and check for an obvious cause, such as snow on the panels. If it keeps showing, look for other codes and call us. |
| State 567 (Fronius Symo Hybrid) | Output reduced because the grid voltage is too high | Wait: it clears when the grid voltage is back in range. If it keeps coming back, call us. |
When to call an engineer
Call us if you see any of these:
- A State code that shows all the time or keeps coming back
- State 306 or State 307 in good sunlight
- State 509 with no obvious cause, such as snow
- Any code that isn’t in the table
Fronius says servicing is for suitably qualified people, and many State codes need a Fronius-trained service engineer. Don’t open the inverter or work on its cables yourself.
Call 0800 156 0191 or use the fault finder below.
Why L&R Renewables
Any installer’s system
It doesn’t matter who fitted your Fronius inverter or whether they’re still trading.
Certified, in-house engineers
We’re MCS and NAPIT registered and TrustMark approved, and our own engineers carry out every job.
Honest about repair versus replacement
If a repair will do the job, that’s what we recommend.
England, Wales & Scotland
We cover England, Wales and Scotland.
Frequently asked questions
What does Fronius State 509 mean?
It means the inverter hasn’t fed any energy into the grid for the past 24 hours. Snow on the panels can cause it. If there’s no obvious reason, check the display for other State codes, because 509 is usually a sign of another fault, and call us if it keeps showing.
Why does my Fronius inverter show State 306 in the morning?
State 306 means the panels aren’t yet producing enough power to feed the grid. Fronius notes that it’s normal early in the morning and in the evening. If you see it in good sunlight, there may be a fault on the panel side, and it’s worth having the system checked.
Do these State codes apply to Fronius GEN24 inverters?
No. GEN24 inverters use a different numbering system, with four-digit codes shown in the inverter’s web interface and in Solar.web. Tell us the code and the model, and we’ll look into it.
My installer has gone bust. Can you still help?
Yes. We don’t need the original installer to be involved, and we provide the certification and documentation for any new inverter we fit.
Do you cover my area?
Our engineers cover England, Wales and Scotland. Call 0800 156 0191 or tell us your postcode in the fault finder and we’ll confirm cover for your area.
Related pages
Solar inverter repair
Repair and replacement for every major inverter brand.
Solar panel repair
Diagnosis and repair for the whole system, from any installer.
Solar panel servicing
An annual health check that catches faults early.
Tell us what your Fronius inverter is doing
Answer four quick questions — including the error code — and leave your details, and we’ll call you back to arrange a visit. Prefer to talk? Call 0800 156 0191, Monday to Friday, 9:00am–5:00pm.
Solar fault finder
What’s happening with your system?
What make is your inverter?
Roughly how old is the system?
Where is the property?
Leave your details and we’ll be in touch to book your initial visit.
We’ll ring you to talk it through and arrange a convenient time. Your answers above go with your enquiry, so you won’t have to repeat them.
We’ll talk through what’s happening and book your initial visit. If it’s urgent, call 0800 156 0191.
Rather talk now? Call 0800 156 0191 — free from UK landlines and mobiles.
You can also reach us through our contact page.