Prompt and useful support regarding my Sunsynk system lack of performance. Ronald simplified the technical issues to make them understandable. Many thanks, looking forward to follow up.
Patrick Keenan · May 2026 Trustpilot
Brand support · Fronius
Fronius Inverter Support — State Codes, Isolation Faults & Aging Capacitors
One of the UK's most established string inverter brands — Primo and Symo units installed from 2012. State codes, isolation faults, grid disconnection, aging capacitors — we diagnose Fronius systems from Solar.web data and event logs. Remote-first. Independent from Fronius and your installer.
Free remote diagnostic £125 only if we fix it remotely
- Not affiliated with Fronius
- Primo, Symo & SnapINverter legacy
- Capacitor replacement assessment
Not sure where to start?
State code error or isolation fault — we diagnose Fronius systems remotely in a single session. Solar.web offline? Follow our free Solar.web offline guide, and if the Datamanager still won't connect, we can set it up on site, from £195.
Book your free remote diagnosticSolar.web offline guideSafety: do not open inverter enclosures. If the inverter displays an isolation fault, do not repeatedly restart — this does not fix the fault.
Had issues with 10yr+ installation. 1 inverter going into alarm mode, unable to access monitoring apps and wanted someone to review and document worthiness of the 2 systems I have. As you will find with older systems, the original installers have moved on, other companies only want to replace and install new, or make up silly prices as they don't want the work, so struggling for 18 month plus trying to source someone to do this. Ronald managed to fit me in the day after contact as he was in the area. Spent a couple of hours on site, found issue with the inverter alarm and he monitoring this to find a total solution, got me back onto the monitoring apps, provided a report on the installations and identified potential areas of concern. These are the people you need for diagnostic reviews of your installations, long term industry professionals, who have a wealth of knowledge gained through working in the industry, know the differing systems and how to contact and approah the companies involved. These are the people you need if you are having issues with installers and / or product and/or supply companies.
M Foster · Jul 2026 Google
Wow... a firmware update to my inverter sent the whole system into meltdown – the battery discharged, and the house seemed to be drawing power, and the solar, who knows where that was going? Aghhh... A short email exchange with Roland and Solar Tech Support sorted the problem... the firmware had reversed a setting (from when it was installed), and the CT clamp needed to be reversed. As soon as I had done that, the world returned to normal. Thanks, Roland; there is no way I would have come to that conclusion. Would I recommend them? You bet! Worth the fee? You bet, again!
Pete Hawkins · Jul 2026 Google
We were having problems with our inverter, couldn’t get an early response from our installer a stressed conversation between our installer and solar tech support led to a text to us to authorise connection to your company . Ron was a very helpful and knowledgeable man who tried with a bit of difficulty as we are pensioners and very knowledgeable. Spent time on phone without making us feel small.we would recommend this company if you have any problems. Thanks Ron 5 star
Me and the boss · Aug 2026 Trustpilot
After 6 months of trying to find someone to help with non functioning Givenergy batteries and inverter, I contacted Ron at STS who remotely sorted the problem within days. Highly recommended.
Francesca Pomlett · Oct 2026 Google
Ronald at Solar Tech Support was very quick and knowledgeable in helping me restart my GivEnergy solar electric battery. I would highly recommend his services.
Thomas Croke · Aug 2026 Google
Fronius Faults
Common Fronius problems we diagnose
Every fault below has a proven diagnostic path. Click through for the specific page or book a diagnostic if you're unsure.
Inverter & Production
Alarm
State code alarm (xxx.yyy format)
Fronius displays state codes on the LED display and in Solar.web event log. Format xxx.yyy indicates fault category and specific event. Common codes: 102.x (grid fault), 401.x (isolation fault), temperature events. Diagnosis requires checking the exact code and timestamp.
See diagnostic guide →Common
No solar production
Inverter powered but generating zero power. Could be a DC string fault, isolator not closed, or protection trip not cleared. Check Solar.web historical data and string-level metrics to identify the fault pattern.
See diagnostic guide →Performance
System underperforming
Inverter generating below expected output for conditions. May indicate soiled panels, partial string shading, or internal component degradation. Solar.web data analysis reveals the loss pattern over time.
See diagnostic guide →Grid & Isolation
Safety Stop
Isolation fault / earth fault
Inverter has measured a drop in DC-to-earth resistance below the safe threshold. Common causes: water ingress into MC4 connectors, cracked cable insulation from UV, or failed panel junction box. Do not repeatedly restart — this is a genuine safety fault requiring investigation.
See diagnostic guide →Grid Fault
Grid overvoltage / frequency fault
AC voltage or frequency at grid connection has exceeded safe limits. Common in solar-dense streets where export raises local grid voltage. May clear automatically or require export limit configuration and DNO notification.
See diagnostic guide →Technical
Capacitor aging / internal fault
Age-related component failure common in Fronius units from 2012–2018. Causes intermittent shutdowns, output reduction, and eventually complete failure. Capacitor replacement is viable on well-maintained units under 10 years old.
See diagnostic guide →Monitoring & Connectivity
Common
Solar.web offline / app not updating
Portal shows no data. Caused by Fronius Datamanager communication card losing internet connection. Router change, WiFi password update, or broadband failure. The system usually keeps running, but offline doesn't prove it, so check the inverter's own screen.
See diagnostic guide →Setup
WiFi / Datamanager not connecting
Fronius Datamanager card unable to find WiFi network. Requires reconfiguration via the Datamanager setup wizard (accessible at inverter IP address on local network) or Fronius Solar.web app Bluetooth setup. If it still won't connect, we can set it up on site, from £195.
See diagnostic guide →
Fault Codes
Fronius state code index
Seeing an error code in Solar.web or on the inverter display? Our full Fronius state code index explains what each code means, common causes, and safe next steps.
Fault code categories
·Grid & AC faults (1xx series) — voltage, frequency, phase
·Isolation & DC faults (4xx series) — earth isolation, string issues
·Temperature & hardware faults — thermal events, component failures
·Communication & monitoring errors — Datamanager, portal issues
Services
All services →
What we do for Fronius owners
Remote Fronius Diagnostic
We review Solar.web data, inverter settings, and fault history to identify the exact fault without a site visit.
✓ State code root-cause analysis
✓ Solar.web data review
✓ Written engineer summary
Fronius System Recovery
Installer gone bust, Solar.web access lost, or monitoring never set up correctly? We recover access and rebuild documentation.
✓ Solar.web access recovery
✓ On-site WiFi setup, from £195
✓ Warranty evidence pack
On-Site Fronius Repair
Isolation fault investigation, DC cable fault location, capacitor replacement assessment, component repair. Targeted visit — no guesswork on arrival.
✓ Evidence-led targeted checks
✓ Safety-focused report
✓ Repair or replacement path
Documents
Fronius datasheets, manuals & warranty PDFs
Download datasheets, installation manuals and warranty documents for Fronius Symo inverters and battery systems. Self-hosted and always current.
Product datasheets & specifications
Installation & commissioning manuals
Warranty terms & coverage documents
App & software setup guides
Wiring diagrams
About Fronius systems — what you need to know
Fronius is one of the UK's most established solar inverter manufacturers. The Primo (1–15kW single-phase) and Symo (3–25kW three-phase) ranges have been installed since 2012, making them some of the oldest string inverters still in widespread use. The legacy SnapINverter series (Galvo) from 2012–2018 is also still supported.
Fronius inverters are string inverters — no optimizers, whole-string MPPT. State codes (xxx.yyy format) are the standard fault language — the first three digits identify the fault category (102 for AC grid, 401 for isolation), decimal digits for specific events. Isolation faults are most serious — they indicate DC-to-earth resistance drop and trigger automatic shutdown for safety.
The Solar.web portal and app are powered by the Fronius Datamanager communication card. Many units from 2012–2018 are now 8–12 years old and approaching capacitor end-of-life. Capacitor degradation is the most common age-related failure causing intermittent shutdowns and output reduction. If you're searching for Fronius repair UK, Fronius state code, Fronius isolation fault, Fronius Solar.web offline, or Fronius capacitor replacement, STS provides independent diagnostic and repair support across the UK — not affiliated with Fronius.
Related problem pages
We also support
STS supports all major inverter and battery brands — not just Fronius. If you have a mixed-brand system or are comparing options, visit the brand hub.
Browse all brandsExplore
More Fronius help
Fronius common problems & faults
Independent Fronius problems support across the UK — 4 faults STS engineers diagnose and repair. Free remote diagnostic, no fix no fee.
See Fronius common problems & faultsFault codes
Complete index of Fronius inverter fault codes and state codes — what each code means, causes, and where to find them in Fronius Solar.web and Fronius Home App.
See fault codesDocuments & downloads
Download Fronius datasheets, installation manuals, warranty PDFs, app guides and wiring diagrams. Free remote diagnostic — no fix, no fee. Same-day.
See documents & downloadsFronius questions answered
State codes appear on the inverter LED display or in Solar.web event log. Format xxx.yyy — first three digits identify fault category (102 = AC grid, 401 = isolation), decimal digits identify specific event. Find your code: in Solar.web go to Current Data > Inverter Status, or on inverter press button to scroll display. Note exact code and timestamp. See code decoder →
Isolation fault means inverter measured a drop in DC-to-earth resistance below safe threshold. Common causes: water ingress into MC4 connectors, cracked cable insulation from UV, or failed panel junction box. It's a genuine safety event — inverter shuts down to protect the grid. Do not repeatedly restart; this does not fix the fault and may make diagnosis harder. Isolate system and book an inspection.
If inverter is generating but Solar.web shows no data, the Fronius Datamanager communication card has lost internet connection. This happens after router changes, WiFi password updates, or broadband failures. Access Datamanager setup wizard by navigating to inverter's IP address on local network (found in router DHCP list), or use Fronius Solar.web app Bluetooth setup to reconnect. If it still won't connect, we set it up on site, from £195: we connect it to your WiFi, set up your router, including a separate 2.4 GHz network if it needs one, and check it's reporting.
Fronius SnapINverter (Galvo, Primo) units from 2012–2018 are now 6–12 years old. Capacitor degradation is most common age-related failure — causes intermittent shutdowns, output reduction, eventually complete failure. Capacitor replacement is viable and cost-effective on units less than around 10 years old if otherwise well-maintained. We assess repair-vs-replace decision remotely using Solar.web historical data.
Book
Ready to fix your Fronius system?
Tell us what's happening. We'll review your details and come back with a clear diagnosis path — usually same day.
- Not affiliated with Fronius
- No fix, no fee covers remote fixes. On-site work is quoted in writing before we start.
- On-site visits available
Service notice
We’re busier than ever. Thank you for your patience.
Due to unprecedented demand we’re currently only carrying out on-site work in Yorkshire, and replies are taking up to 7 days. Remote diagnostics continue for the whole UK as normal.
Every message is read and answered, so please don’t send it twice; that only slows the queue.
Ronald Director, Solar Tech Support
On-site: Yorkshire only, for now
Remote: UK-wide, as usual
Remote fix: £125 if we fix it, no charge if we don’t
Replies: within 7 days
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