Problem diagnosis · Fronius

Fronius Grid Overvoltage — Frequency Fault & State 102

Your Fronius inverter is disconnecting because the grid voltage at your property exceeds 253 volts — the upper limit set by UK grid code G98. This is not an inverter fault. It is a network issue, and it is increasingly common on UK streets with multiple solar installations.

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Losing generation every sunny afternoon?

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.

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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 →

UK grid voltage limits (G98 / G99)

Nominal — 230V AC

Permitted range — 216V to 253V

Trip threshold — above 253V

The inverter disconnects automatically when voltage exceeds the upper limit. It reconnects after approximately 60 seconds once voltage returns to the safe range.

Diagnostics

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.

Reference

Grid-related Fronius state codes

102

AC voltage too high

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.

103

AC voltage too low

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.

104 / 105

Frequency outside limits

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.

107

No grid detected

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.

108

Island operation detected

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 — all brands

Grid overvoltage — common questions

What causes Fronius state 102 grid overvoltage?

State 102 triggers when grid voltage exceeds 253V — the UK G98 upper limit. The most common cause is high solar penetration on your local network. When multiple homes export simultaneously, the combined feed-in pushes voltage above the safe threshold. This is worse on rural networks with weak infrastructure and transformers set to high baseline voltages. The inverter is working correctly — it disconnects as required by regulation.

Why does my Fronius inverter keep tripping on overvoltage?

Recurring trips during sunny afternoons mean grid voltage in your area is consistently near or above 253V when solar systems export. This is a network infrastructure problem, not an inverter fault. The transformer serving your area may have its tap set too high. Contact your Distribution Network Operator — they can adjust the tap, lowering baseline voltage by 5–10V to create headroom for solar export.

Can Fronius voltage trip settings be adjusted?

Fronius inverters have configurable voltage protection parameters, but they are locked to the G98/G99 country setup for UK installations. A qualified installer can make limited adjustments within the range permitted by the grid code, but the trip threshold cannot be raised above the regulatory limit. Persistent overvoltage above 253V requires a network-level fix from the DNO rather than an inverter settings change.

What is the difference between a voltage fault and a frequency fault?

Voltage faults (102, 103) are caused by local network conditions — the voltage at your property is too high or too low. These can be persistent, recurring daily. Frequency faults (104, 105) are caused by system-wide grid events — a sudden imbalance between generation and demand nationally. Frequency faults are typically brief, self-correcting, and rare. If you see state 104 or 105 regularly, it may indicate an inverter measurement issue rather than a genuine grid frequency problem.

How much generation am I losing to grid overvoltage trips?

It depends on how frequently the inverter trips. Each event triggers a minimum 60-second disconnection. If voltage stays high, the inverter trips again immediately after reconnecting — creating repeated cycles during peak sun. In severe cases, homeowners lose 20–40% of potential midday generation. STS can analyse your Solar.web data to calculate the actual loss and provide evidence for your DNO complaint.

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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.

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Free remote diagnostic · no fix, no fee
DNO complaint evidence included

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