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Problem diagnosis · Sofar Solar

Sofar Grid Disconnection Fault — G98/G99 Voltage & Frequency Trip Diagnosis

Your Sofar inverter keeps dropping off the grid with a fault alarm. It's not failing — it's protecting the network. Grid overvoltage, frequency excursion, or isolation fault — each has a different cause and fix. This guide walks through how to read the fault codes and determine what's happening.
  • G98/G99 voltage and frequency limits
  • Covers HYD hybrid and ME3000SP
  • SolarMan event log diagnosis
Frequent grid disconnections?

We review your SolarMan event log, check grid code configuration, and determine whether the trips are caused by grid voltage, system settings, or an isolation fault.

Book your free remote diagnosticBack to Sofar hub

Independent — not affiliated with Sofar Solar.

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

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
ℹ️

Important: A grid disconnection is a safety function, not a system failure. Your Sofar inverter is doing exactly what the UK grid code requires — disconnecting when voltage or frequency exceeds safe limits. The system reconnects automatically when conditions normalise.

Diagnostics

5-step grid disconnection diagnosis

Sofar inverters report grid faults with specific codes: G-OV (overvoltage), G-UV (undervoltage), G-OF (overfrequency), G-UF (underfrequency), and G-ISO (isolation fault). The code tells you exactly which diagnostic path to follow.

1

Check SolarMan for the grid fault code

Log into SolarMan and navigate to the alarm or event history. Find the grid disconnection event and note:

Fault code — G-OV, G-UV, G-OF, G-UF, or G-ISO
AC voltage at the time of disconnect
Grid frequency at the time of disconnect
Time of day — midday trips suggest solar export pushing voltage up
Sofar grid fault codes
G-OV: Grid overvoltage — AC above 253V for more than 200ms
G-UV: Grid undervoltage — AC below 207V for more than 200ms
G-OF: Grid overfrequency — above 52Hz for more than 200ms
G-UF: Grid underfrequency — below 47.5Hz for more than 200ms
G-ISO: Isolation fault — DC insulation resistance below safety threshold

For ME3000SP units, check the LCD display for the most recent fault code. The ME3000SP logs faults locally as well as in SolarMan (if the datalogger is connected).

2

Determine if the fault is grid quality or isolation

Grid disconnection faults split into two distinct categories:

Grid quality (G-OV, G-UV, G-OF, G-UF)

The AC grid voltage or frequency has exceeded statutory limits. This is an external issue — the local electricity network is out of specification. The inverter disconnects as required by G98/G99 and reconnects when conditions normalise.

Isolation fault (G-ISO)

The insulation between DC circuits and earth has degraded. This is an internal system issue — water ingress into connectors, damaged cable insulation, or a battery module fault. Requires on-site testing with an insulation resistance meter.

The diagnostic path is completely different for each category. Grid quality faults require monitoring and possibly DNO engagement. Isolation faults require on-site DC testing.

3

Check the grid code configuration

In SolarMan, check the grid code setting under device configuration:

G98: For installations up to 3.68kW per phase. Standard UK voltage and frequency protection limits. Can connect without prior DNO approval.
G99: For larger systems. Requires formal DNO application and acceptance. Additional reactive power and frequency response requirements.

If the inverter still has a factory default grid code from another country, the voltage and frequency thresholds will be wrong — causing disconnections at voltages that are normal for the UK grid. This is particularly common on recently installed or replaced Sofar inverters where the commissioning was incomplete.

Grid code settings require installer-level access in SolarMan. If you need to change it, contact STS or a qualified installer.

4

Monitor voltage patterns over 3–5 sunny days

If the fault code is G-OV, track the AC voltage in SolarMan across several sunny days to establish a pattern:

Note the time of each trip — midday trips correlate with peak solar export
Record voltage at disconnect — consistently above 250V confirms grid overvoltage
Check if it happens on cloudy days — if no trips on overcast days, solar export is the trigger
Ask neighbours with solar — if their systems trip at the same time, it confirms a local grid issue

For HYD hybrid systems with battery storage, switching to self-consumption mode during peak solar hours can reduce export and lower your contribution to local voltage rise.

5

Contact your DNO or configure export limiting

If grid overvoltage is persistent, you have two parallel options:

1. Report to your DNO: Provide SolarMan screenshots showing AC voltage above 250V at each disconnect. Your DNO is responsible for maintaining voltage within statutory limits. They may adjust the local transformer tap, upgrade distribution cables, or authorise an export limit.
2. Configure export limiting: Setting an export limit on the Sofar inverter reduces peak export power and lowers the voltage rise. For HYD hybrids, this is configured in SolarMan. For the ME3000SP, export behaviour is managed through charge and discharge schedule settings.

Export limiting reduces your Smart Export Guarantee income but keeps the system connected during periods when it would otherwise trip. For HYD systems with battery, self-consumption priority achieves a similar effect by charging the battery instead of exporting.

Sofar grid faults — HYD hybrid vs ME3000SP

Sofar has two distinct product families in the UK, and grid disconnection faults manifest differently on each. The HYD hybrid series (HYD 3600–6000 EP) are all-in-one inverters that handle solar MPPT, battery management, and grid connection. They report grid faults through SolarMan with detailed voltage and frequency data. Because HYD systems have battery storage, they have a built-in advantage — excess solar can charge the battery instead of exporting, reducing contribution to local voltage rise.

The ME3000SP is an AC-coupled system that sits alongside a separate solar inverter. It manages battery charge and discharge but does not control the solar inverter's grid connection. If the solar inverter trips on grid overvoltage, the ME3000SP continues operating normally — it only trips if the voltage exceeds its own AC coupling point limits. This means you may see the solar inverter disconnecting while the ME3000SP stays online, or vice versa, depending on where the voltage threshold is breached first.

For both product families, the underlying cause of grid overvoltage trips in the UK is the same: grid infrastructure that was not designed for the level of distributed solar now connected to it. As solar installations increase in suburban areas, the cumulative export during peak hours pushes local voltage above G98 limits. This is a network-level problem, not a Sofar fault.

Back to

Return to the Sofar brand hub to explore other common faults and services.

Sofar support hub
FAQ

Grid disconnection fault — common questions

Sofar inverters disconnect when grid voltage or frequency exceeds G98/G99 limits. The most common UK cause is grid overvoltage at midday — local voltage rises above 253V when multiple solar systems export simultaneously. This is a grid infrastructure issue, not an inverter fault. The system reconnects automatically when conditions normalise.
G-OV is grid overvoltage (above 253V). G-UV is undervoltage (below 207V). G-OF is overfrequency (above 52Hz). G-UF is underfrequency (below 47.5Hz). These are G98 protection thresholds — the inverter disconnects automatically when any is exceeded for more than 200 milliseconds and reconnects when conditions return to normal.
For HYD hybrids, log into SolarMan and check the alarm or event history — each disconnect is logged with the fault code, timestamp, voltage, and frequency. For ME3000SP units, check the LCD display or SolarMan if the datalogger is connected. The code tells you whether the trip was grid quality (G-OV/UV/OF/UF) or isolation (G-ISO).
No. Grid disconnection is a designed safety function. The inverter disconnects to protect both the system and the grid — no damage occurs. Frequent trips reduce generation during disconnect periods but do not cause wear or degradation. The system reconnects and resumes normal operation automatically.
G-ISO means the insulation resistance between DC circuits and earth has fallen below the safety threshold. Unlike grid voltage faults, this is internal to your system. Common causes include water ingress into MC4 connectors, UV-damaged cable insulation, or a battery module fault. A G-ISO fault requires on-site testing with an insulation resistance meter. Book a diagnostic and we'll confirm the cause.
Book

Sofar inverter keeps tripping off the grid?

We review your SolarMan event log, check grid code configuration, and determine whether the trips are caused by grid voltage, frequency, or an isolation fault. Clear diagnosis, clear next steps.

  • Free remote diagnostic · no fix, no fee
  • HYD hybrid and ME3000SP covered
  • DNO engagement support if needed

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