Problem diagnosis · Fronius

Fronius State Code Alarm — Inverter Error Codes Explained

Your Fronius inverter is displaying a numbered state code — a status message telling you something abnormal has been detected. Not all codes are faults. Some clear on their own, some need a manual reset, and some need an engineer. The first digit of the code tells you which.

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State code keeps coming back?

A recurring state code means the underlying condition has not been resolved. We review your Solar.web event history remotely to identify the pattern, classify the fault, and recommend the right fix — before booking an unnecessary site visit.

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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

Ian · May 2026 Trustpilot

Sree · May 2026 Trustpilot

Dennis Brown · May 2026 Trustpilot

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

Mr Machin · May 2026 Trustpilot

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

Christopher · Apr 2026 Trustpilot

customer · Apr 2026 Trustpilot

Andy Thomas · Apr 2026 Trustpilot

Philip · Apr 2026 Trustpilot

Fronius hub Isolation fault State code alarm Solar.web offline Grid fault Fault codes →

Quick reference — state code classes

1xx — Temporary grid issue · auto-reconnects

3xx — Operational message · does not stop generation

4xx — Hardware / software fault · may need engineer

5xx — Non-critical notification · acknowledge to clear

Diagnostics

6-step state code diagnosis

Work through these steps to identify what your Fronius state code means, whether it needs action, and what that action should be.

Find the state code on your inverter or Solar.web

Fronius state codes appear in two places. On the inverter itself, the LCD display shows the current state code number and a short description. In Solar.web — Fronius's monitoring portal — the event log records every state code with a timestamp, so you can see exactly when each event occurred and how long it lasted.

Open Solar.web, navigate to your system, and check the event log. Write down the exact code number and when it first appeared. If the inverter display is showing a code but the system is still producing power, that is a Class 3 informational code. If production has stopped entirely, the code is more likely Class 1 (grid) or Class 4 (hardware).

Identify the code class from the first digit

The first digit of the state code tells you the severity and whether you need to act:

• 1xx — Grid issues — the inverter has disconnected because grid voltage or frequency is outside safe limits. It will reconnect automatically when the grid stabilises. State 102 (voltage too high) is the most common in this class.

• 3xx — Operational — informational messages during feed-in. State 306 (power low) and 307 (voltage low) appear at dawn and dusk when there is not enough sunlight to generate — this is completely normal.

• 4xx — Hardware fault — the inverter has detected a component failure. State 407 (temperature sensor), 401 (communication), and 457 are the most common. These usually need an engineer.

• 5xx — Notifications — non-critical messages that display until you acknowledge them. State 509 (no feed-in for 24 hours) is the most common and may indicate snow cover, heavy soiling, or a genuine fault.

Check whether the code is temporary or persistent

Open the Solar.web event log and look at the pattern over time. A code that appeared once during a grid disturbance and cleared on its own is temporary — no action needed. A code that appears every day at the same time, such as state 102 every sunny afternoon, points to a recurring grid overvoltage issue that may need investigation.

State 306 and 307 appearing only at dawn and dusk are completely normal — they indicate insufficient light for feed-in. A Class 4xx code that persists after a restart is a hardware fault. The key question is whether the code is reducing your energy production during the hours when the system should be generating.

Try a manual reset for non-hardware codes

For Class 1xx and 5xx codes, pressing the button on the inverter display clears the alarm and lets the inverter attempt reconnection. For a full power cycle:

1. Switch off the AC isolator at the consumer unit

2. Switch off the DC isolator below the inverter

3. Wait three minutes for the capacitors to discharge

4. Switch the DC isolator back on, then the AC isolator

5. Allow five minutes for the inverter self-test to complete

If the code returns immediately after restart, do not keep cycling the power. The fault is persistent and needs professional diagnosis. Class 4xx codes that return after a reset confirm a genuine hardware problem.

Review the Solar.web event history for patterns

The most useful diagnostic information is the pattern over time. Check the event log covering at least the last 30 days and look for correlations:

• State 102 every sunny afternoon — grid overvoltage from high solar export in your area. Multiple homes feeding in simultaneously pushes the local voltage above the safe limit.

• State 509 after several cloudy days — check panels for snow, heavy soiling, or bird mess before assuming a fault.

• A 4xx code with a matching drop in daily yield — confirms the fault is actively reducing your production and needs attention.

This event history is exactly what a diagnostic engineer needs to identify the root cause remotely — without an unnecessary site visit.

Book a diagnostic if the code keeps returning

If a state code is recurring and affecting your energy production, it needs professional diagnosis. STS reviews your Solar.web event log and production data remotely to identify whether the issue is grid-related, weather-related, or a hardware fault — before anyone visits the property.

For grid overvoltage issues (state 102), the solution may involve contacting your Distribution Network Operator. For hardware faults (4xx), the engineer can identify the likely component before attending site — reducing diagnosis time and cost.

Why state code 102 is increasingly common across the UK

State 102 — AC voltage too high — is the most common recurring Fronius state code in the UK. The inverter disconnects because it has measured grid voltage above the safe threshold, typically above 253 volts on the UK nominal 230V supply. It reconnects automatically when the voltage drops, but if this happens repeatedly during peak sun hours, the system loses significant generation.

The underlying cause is grid infrastructure that was not designed for widespread solar export. On rural and suburban networks with multiple solar installations, simultaneous export during midday pushes the local voltage upward. The houses furthest from the transformer see the highest voltage and are the first to trip. This is a network issue, not an inverter fault — reporting it to the Distribution Network Operator is the correct next step, as they may need to adjust the transformer tap or reinforce the local network.

Fronius inverters operating under G98/G99 grid codes in the UK have specific voltage and frequency trip settings. In some cases, an installer can adjust the voltage threshold within the allowed range to reduce nuisance tripping — but this must be done by a qualified person with access to the inverter service menu and only within the parameters permitted by the grid code.

Reference

Most common Fronius state codes in the UK

102

AC voltage too high

Grid voltage exceeds the safe limit. Common on networks with high solar penetration. Auto-reconnects when voltage drops. Report to DNO if it happens daily.

306 / 307

Power low / voltage low

Insufficient DC power or voltage to feed in. Normal at dawn and dusk. Only a concern if it appears during peak sun hours — check for panel shading, soiling, or a DC wiring issue.

407

Temperature sensor faulty

Heat sink temperature sensor has failed or disconnected. Hardware fault — try a power cycle first. If it returns after restart, the inverter needs professional repair.

509

No feed-in for 24 hours

The system has not generated for a full day. Check for snow, heavy soiling, or a tripped AC breaker before assuming a fault. If panels are clean and breakers are on, the inverter needs investigation.

475 / 502

Isolation fault / earth fault

DC insulation resistance has dropped below the safe threshold. Almost always caused by water ingress. Do not restart — see our dedicated isolation fault guide.

System not producing — all brands

State code alarms — common questions

What is a Fronius state code alarm?

A state code is a numbered status message that Fronius inverters display when they detect an abnormal condition. Class 1xx codes are temporary grid issues, 3xx are operational messages during low light, 4xx are hardware or software faults, and 5xx are non-critical notifications. Not all state codes are actual faults — many represent normal operating conditions such as insufficient light at dawn and dusk. The code appears on the inverter LCD and is logged in Solar.web with a timestamp.

Why does my Fronius inverter show state 102?

State 102 means the grid voltage at your property is too high. The inverter disconnects to protect itself and the network, then reconnects automatically when the voltage drops. In the UK, this commonly happens on rural or suburban networks with high solar penetration — when multiple systems export simultaneously, local voltage rises above the 253V limit. If it happens daily during peak sun, the grid in your area may need reinforcement. Contact your Distribution Network Operator to report the issue.

Can I reset a Fronius state code myself?

For Class 1xx and 5xx codes, yes — press the button on the inverter display to clear the notification, or do a full power cycle by switching off the AC isolator then the DC isolator, waiting three minutes, and switching them back on in reverse order. Class 3xx codes clear automatically when conditions improve. However, Class 4xx codes that return after a reset indicate a hardware fault that needs professional diagnosis. Repeatedly power-cycling an inverter with a persistent 4xx code will not fix it.

What does Fronius state 407 mean?

State 407 means the temperature sensor on the inverter heat sink is faulty or disconnected. This is a Class 4 hardware fault — the inverter cannot safely monitor its own temperature, so it shuts down as a precaution. Try a full power cycle first. If state 407 returns after restart, the sensor has failed and the inverter needs professional repair or replacement. This fault is more common on older Primo and Symo units where years of thermal cycling degrade the sensor connection.

How do I find state codes in Fronius Solar.web?

Log into Solar.web at solarweb.com, select your system, and navigate to the event log or notifications section. Each state code is recorded with the code number, a short description, and the date and time. You can filter by date range to see patterns over weeks or months. The Solar.web mobile app for iOS and Android also shows current codes and push notifications. If you cannot access Solar.web, the code is also shown on the inverter LCD — press the display button to cycle through current and recent codes.

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Recurring state code? We find the cause remotely.

We review your Solar.web event history and production data to identify whether the issue is grid-related, weather-related, or a hardware fault — before booking a site visit.

Not affiliated with Fronius
Free remote diagnostic · no fix, no fee
Covers all Fronius state code classes

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