My 90-year-old father-in-law had a solar system installed nearly three years ago that never worked properly and kept tripping out. Neither the original installer nor GivEnergy could resolve the issues, and we were even pushed towards replacing the system entirely when GivEnergy went bust. I contacted Ron at Solar Tech Support via WhatsApp, and within a few hours he had diagnosed multiple faults — including incorrect wiring that posed a potential fire risk. He carried out a home visit in Nottingham for £295 (including parts), fixed everything, completed firmware updates, and ensured the system was fully operational. Since then, it has worked perfectly. Ron was knowledgeable, responsive, and took the time to explain everything clearly. Highly recommended — excellent value and complete peace of mind.
Fronius Grid Overvoltage — Frequency Fault & State 102
- Not affiliated with Fronius
- No fix, no fee
- DNO complaint evidence provided
If state 102 trips daily during peak sun, you are losing significant energy production. We quantify the loss from your Solar.web data and provide the evidence your DNO needs to fix the network.
Book your free remote diagnosticBack to Fronius hubIndependent — not affiliated with Fronius International.
A really big thank you to Ron and his team, he has vast amounts of knowledge and got my system back up and running, also good to get on with. I was absolutely lost as to know what to do, no help from installer and somehow came across Ron and am I glad I did. I would definitely definitely recommend him to anyone who has faults with there solar system, any make I would say. Thanks again Ron a pleasure meeting you.
Big thanks to Ron. He was incredibly patient and helpful over the phone, taking the time to walk myself and the installer through every troubleshooting step. Through lots of testing he figured out the issue was definitely a hardware issue, which allows us to consider our next steps. Support fees are clear and they operate a “no fix no fee” policy. It is rare to find that kind of honesty combined with dedicated phone support nowadays. I highly recommend Ron, if you need help with your solar system don’t hesitate to give him a call.
Excellent response to diagnose a problem on our SolarEdge installation. Kept us informed at every step. Diagnosis quickly completed and solution implemented.
Our SolarEdge PV system with LG batteries had its first hiccup after 8 years of hard work. The Inverter failed. Fortunately I found Solar-Tech-Support who diagnosed the problem very quickly, ordered a replacement unit and fitted it shortly after we received the unit from SolarEdge. Very thorough and professional approach. Thank you, a solid 5 star recommendation.
Ronald was great to help me sort out my giv energy inverter issue since company has gone bankrupt in april 26.
The inverter disconnects automatically when voltage exceeds the upper limit. It reconnects after approximately 60 seconds once voltage returns to the safe range.
6-step grid overvoltage diagnosis
Grid overvoltage is a network problem, not an inverter fault. These steps help you identify whether the issue is one-off or persistent, and what to do about it.
Identify which grid fault code you are seeing
Fronius uses several state codes for grid conditions. State 102 (AC voltage too high) is the most common — the inverter has detected voltage above the 253V G98 limit. State 103 means voltage too low. States 104 and 105 indicate grid frequency outside the permitted 50 Hz range. State 107 means no grid detected, and state 108 means the anti-islanding protection has triggered.
Check the inverter display or the Solar.web event log for the exact code, timestamp, and how often it has occurred. A single state 102 event during unusual grid conditions is not a concern — a daily pattern is.
Understand that this is a grid issue, not an inverter fault
All 1xx state codes are protective responses to abnormal grid conditions. The inverter is working exactly as it should — it has detected that the electricity network at your property is outside safe limits and has disconnected as required by UK grid code G98.
The inverter reconnects automatically after approximately 60 seconds once grid conditions return to normal. You do not need to reset it manually. If voltage remains high, the inverter will trip again — creating a cycle of short disconnections that costs you generation during the best producing hours of the day.
Check for a recurring overvoltage pattern
Open the Solar.web event log and review the last 30 days. State 102 appearing every sunny afternoon between midday and 3pm is the classic pattern. Multiple solar systems on your street are exporting simultaneously, pushing the local voltage above 253V.
This is increasingly common across the UK as solar adoption grows — particularly on rural networks with long distribution lines, weak infrastructure, and transformers that were set to high baseline voltages before solar was widespread. The combined export from several homes creates a cumulative voltage rise that the local network was not designed to handle.
Monitor your grid voltage
If your system has a Fronius Smart Meter, you can see real-time grid voltage in Solar.web. Even without one, the inverter logs the voltage at the time of each state 102 event.
Look at the peak readings. Grid voltage consistently above 248V during daylight hours means there is very little headroom before the 253V trip threshold. Anything regularly above 250V with solar export active is a strong indicator that the network transformer tap is set too high for the level of solar generation now connected in your area.
Report persistent overvoltage to your DNO
If state 102 is recurring and costing you generation, contact your Distribution Network Operator (UK Power Networks, National Grid, Northern Powergrid, etc.). Provide your Solar.web event log showing dates, times, and frequency of trips. Request that they fit a voltage monitor at your property.
The most common DNO fix is adjusting the transformer tap setting — lowering the baseline voltage by 5 to 10 volts to create headroom for solar export. This is a straightforward change that resolves overvoltage for all properties on that transformer.
If the DNO is unresponsive, escalate to Ofgem (the energy regulator), then the Energy Ombudsman if still unresolved.
Consider export limitation as a temporary measure
While waiting for the DNO to act, export limitation can reduce the frequency of overvoltage trips. A Fronius Smart Meter measures grid voltage in real-time and automatically reduces inverter output when voltage approaches the trip threshold. The system still generates for self-consumption but reduces export during high-voltage periods.
Export limitation does not fix the underlying grid problem — it is a mitigation that prevents generation loss while the DNO resolves the network issue. STS can assess whether this is appropriate for your situation and configure it remotely.
Why rural UK networks are hit hardest by grid overvoltage
UK distribution transformers have adjustable output taps — typically five to nine positions, each representing a 2.5% voltage step. Rural transformers were historically set to the highest tap to compensate for voltage drop over long distribution lines to remote properties. With no solar generation and low daytime load, this worked well for decades.
The problem appeared when rooftop solar became widespread. To export power, an inverter must push at a voltage slightly higher than the grid. On a rural network where the transformer is already delivering 245 to 250 volts at the nearest properties, even a small amount of solar export pushes the voltage above the 253-volt trip threshold. On a street where four or five homes have solar, the cumulative effect makes overvoltage a daily occurrence during peak sun.
Urban networks are less affected because they have shorter distribution lines, lower impedance, more customer loads consuming power during the day, and transformers set to lower baseline voltages. The long-term solution is for DNOs to adjust transformer taps downward and, in some areas, install active voltage management equipment. Until that happens, affected homeowners lose generation during the most productive hours.
Grid-related Fronius state codes
Grid voltage above 253V. The most common grid fault in the UK. Auto-reconnects after ~60 seconds when voltage drops. Report to DNO if recurring.
Grid voltage below 216V. Less common than overvoltage. May indicate a weak supply connection, a high-draw appliance on the same circuit, or a wider network brownout.
Grid frequency has drifted outside the permitted 50 Hz range. Caused by system-wide grid events, not local conditions. Usually brief and self-correcting. Rarely recurring.
The inverter cannot detect the grid at all. Check the AC isolator at the consumer unit, the main breaker, and whether there is a wider power cut in your area.
Anti-islanding protection has triggered. The inverter detected it may be powering a section of the grid independently — a safety hazard for line workers. Reconnects automatically once the grid is confirmed stable.
Grid overvoltage — common questions
Overvoltage costing you generation? We quantify the loss.
We analyse your Solar.web data to calculate exactly how much energy you are losing to grid trips — and provide the documented evidence your DNO needs to take action.
- Not affiliated with Fronius
- No fix, no fee
- DNO complaint evidence included
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