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.

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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.

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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

Our 3 year old GivEnergy batteries froze. They were showing 0% on the app, but they were fully charged. Some how Ron took over our inverter and remotely cured the problem. We live in King’s Lynn, he is in Leeds I believe. Very grateful.

David Lewin · Jul 2026 Google

Ron was extremely helpful and tried his best to repair/reset our GivEnergy inverter remotely. In the event he was unsuccessful but he couldn’t have been more helpful. If you have problems with a GivEnergy system please contact him. Highly recommended

Neil Crichton · Jun 2026 Google

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.

Steve M · Jun 2026 Google

My Givenergy battery stopped working nearly a month ago. After unsuccessfully reaching out to my installer, who looks like he's also busted, I found Solar Tech Support on a Google search. They fixed my issue in a couple of hours. Any frustrated Givenergy customers, I highly recommend these guys.

Sarma Amirapu · May 2026

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. 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

Keith Ballard · Apr 2026

Steve M · Jun 2026 Google

customer · Apr 2026

ME3000SP EPS fault Grid disconnection Sofar hub →

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.

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).

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.

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.

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.

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.

Grid disconnection fault — common questions

Why does my Sofar inverter keep disconnecting from the grid?

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.

What do Sofar grid fault codes G-OV, G-UV, G-OF, and G-UF mean?

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.

How do I check the grid fault history on my Sofar inverter?

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).

Can a grid disconnection fault damage my Sofar system?

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.

What is a G-ISO isolation fault on a Sofar inverter?

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.

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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.

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DNO engagement support if needed

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