Sofar Inverter Repair and Fault Codes
A red light on your Sofar inverter, an ID code on the screen, or no output at all? We diagnose and repair Sofar inverters from any installer, across England, Wales and southern Scotland.
Repairs you can rely on
- MCS registered
- NAPIT registered
- TrustMark approved
- Fully insured
- Any installer’s system
- In-house engineers — no subcontractors
Call us on 0800 156 0191
Monday to Friday, 9:00am–5:00pm
Is this what you’re seeing?
A red FAULT light on the front of the inverter
An ID code on the screen, such as ID01 or ID12
A green light that keeps flashing in good daylight
“Pv Iso Fault” or “GFCI Fault” on the display
The inverter derating or switching off on hot days
The monitoring shows the inverter offline
Zero output on a bright day
The solar breaker in the consumer unit keeps tripping
Write down the ID number and name on the screen, and the model on the label on the side of the inverter, for example SOFAR 3600TL-G3.
Call 0800 156 0191 or use the fault finder further down this page. If the solar breaker keeps tripping, leave the system switched off until an engineer has looked at it.
Common Sofar faults
Sofar (SOFARSOLAR) inverters were fitted to many UK homes, often on smaller systems. They show faults as an ID number and a name, such as ID01 Grid OVP, with a steady red FAULT light. A green RUN light that flashes means the inverter is waiting or checking before it starts.
Grid faults
ID01 to ID04 mean the grid voltage or frequency is outside the limits the inverter is set to. Sofar says the inverter recovers on its own once the grid is back to normal. If ID01, grid voltage too high, keeps appearing on sunny afternoons, the local grid voltage may be running high and needs checking.
Insulation and leakage faults
ID12 GFCI Fault and ID56 Pv Iso Fault mean leakage to earth, or insulation resistance on the panel side that’s too low. Common causes are water in a connector, a damaged cable or a failed panel. Finding them needs an engineer with an insulation tester. See isolation and earth faults explained. See solar PV electrical testing for how it’s found.
Heat
ID57 and ID58 mean the inverter or its boost circuit has got too hot, and ID81 means it has cut its output to protect itself. Keep the space around it clear. If it keeps happening, ventilation or the inverter itself needs looking at.
Faults inside the inverter
Hardware faults such as ID15 (grid current too high) and ID21 or ID22 (internal chip and power faults) point to a problem inside the inverter. Sofar’s manual suggests a restart for some of these, but if they come back, the inverter needs an engineer.
Repair or replace?
We always diagnose first. Grid trips and earth faults are usually outside the inverter. If the inverter itself has failed, you get a clear written quote before any work starts. Read more about inverter repair and replacement, or see hybrid inverters if you’re thinking of adding a battery at the same time.
Sofar error codes and what they mean
The codes below are from Sofar’s user manual for the single-phase 1.1K to 3.3KTL-G3 inverters. Other Sofar models, such as the three-phase KTLX range and HYD hybrids, can use the same ID number for something different, so tell us your model as well as the code. Don’t open the inverter or disconnect its cables yourself.
| Code | What it means | What to do |
|---|---|---|
| Green RUN light flashing | The inverter is waiting or checking before it starts | Normal at dawn and dusk. If it flashes all day in good light, call us. |
| Red FAULT light | The inverter has a fault | Note the ID code on the screen and call us. |
| ID01 Grid OVP | Grid voltage too high | Clears itself when the grid is normal. If it keeps coming back, call us to check the voltage. |
| ID02 Grid UVP | Grid voltage too low | As ID01. |
| ID03 Grid OFP / ID04 Grid UFP | Grid frequency too high or too low | Usually clears itself. If it persists, call us. |
| ID09 PVOVP | Panel input voltage too high | Call an engineer to check how the panels are wired to the inverter. |
| ID12 GFCI Fault | Leakage current to earth | Call an engineer to test the panel wiring. |
| ID15 HwAc OCP | Grid current too high (hardware protection) | Call us if it comes back after the inverter restarts. |
| ID21 / ID22 | Internal chip or auxiliary power fault | Call an engineer. |
| ID56 Pv Iso Fault | Insulation resistance on the panel side too low | Call an engineer to test the panels and cables. |
| ID57 / ID58 Over Temp | The inverter or boost circuit is too hot | Keep the area around it clear. If it comes back, call us. |
| ID81 Over Temp Derating | Output reduced because of heat | Improve the airflow around the inverter. If it’s frequent, call us. |
When to call an engineer
Call us if you see any of these:
- ID12 or ID56, even if the inverter restarts
- A red FAULT light that doesn’t clear
- ID01 coming back on sunny days
- ID15, ID21 or ID22 coming back after a restart
- Any code that isn’t in the table
Not sure it’s the inverter? Our solar panels not working checklist covers the safe checks you can make first. Call 0800 156 0191 or use the fault finder below.
Why L&R Renewables
Any installer’s system
It doesn’t matter who fitted your Sofar inverter or whether they’re still trading.
Certified, in-house engineers
We’re MCS and NAPIT registered and TrustMark approved, and our own engineers carry out every job.
Honest about repair versus replacement
If a repair will do the job, that’s what we recommend.
England, Wales & southern Scotland
We cover England, Wales and southern Scotland.
Frequently asked questions
What does the red light on my Sofar inverter mean?
A steady red FAULT light means the inverter has detected a fault. The screen shows an ID code and a name, such as ID12 GFCI Fault. Write both down and call us, because most codes behind a steady red light need an engineer.
What is Sofar ID12?
On Sofar’s single-phase G3 inverters, ID12 is a GFCI fault: leakage current to earth. Sofar’s advice is to check whether the insulation resistance between the panels and earth is too low, which needs an engineer with the right test equipment.
Why does my Sofar inverter show ID01?
ID01 Grid OVP means the grid voltage is too high. The inverter disconnects to protect the network and reconnects when the voltage drops. If it happens often on sunny days, we can check the voltage at your property and help you raise it with the network operator.
My installer has gone bust. Can you still help?
Yes. We don’t need the original installer to be involved, and we provide the certification and documentation for any new inverter we fit. See solar installer gone bust? for what else still protects you.
Do you cover my area?
Our engineers cover England, Wales and southern Scotland. Call 0800 156 0191 or tell us your postcode in the fault finder and we’ll confirm cover for your area.
Related pages
Solar inverter repair
Repair and replacement for every major inverter brand.
Solar panel repair
Diagnosis and repair for the whole system, from any installer.
Solar panel servicing
An annual health check that catches faults early.
Other inverter makes we repair: SolarEdge, Fronius, SMA, Growatt, Solis, SolaX and Power-One and ABB Aurora. We work on any make, whoever fitted it. Replacing an old inverter? See our guide to hybrid inverters.
Tell us what your Sofar inverter is doing
Answer four quick questions — including the error code — and leave your details, and we’ll call you back to arrange a visit. Prefer to talk? Call 0800 156 0191, Monday to Friday, 9:00am–5:00pm.
Solar fault finder
What’s happening with your system?
What make is your inverter?
Roughly how old is the system?
Where is the property?
Leave your details and we’ll be in touch to book your initial visit.
We’ll ring you to talk it through and arrange a convenient time. Your answers above go with your enquiry, so you won’t have to repeat them.
We’ll talk through what’s happening and book your initial visit. If it’s urgent, call 0800 156 0191.
Rather talk now? Call 0800 156 0191 — free from UK landlines and mobiles.
You can also reach us through our contact page.