Seeing a fault or error message appear on your inverter can be alarming but knowing what the fault means and how to repair it yourself or when to get the specialists in can help put your mind at ease. As one of the most experienced solar installers in the South East, SolarTherm UK and Silvercrest Energy Group have installed almost every inverter brand that has been manufactured for Solar PV integrated systems in the UK and EU.
Some inverter faults will be temporary and easy to clear, while others may diagnose a serious fault requiring replacement parts or a replacement inverter. Common signs of an inverter fault can include flashing red or orange lights, error messages, inverter fault codes or no power output. Common issues with a solar inverter include power overloads, connection and wiring issues, overheating and battery issues.
This article will look at the brands we use (used) at SolarTherm UK and the most common fault codes we encounter.
Aurora/Power One
A very popular inverter, originally Italian made and later taken over by ABB. If you have this inverter (circa 2011-2016) then your warranty will almost definitely be out. We have tried to repair this inverter many times including sending these inverters historically off to specialist electronics companies in the UK and The Netherlands. The result is these are uneconomical to repair, and we would usually offer a newer brand and type of inverter to suit.
| Error Code | Description |
| E502 | No production – could be for a variety of issues, including a faulty inverter. Check cables for loose connections. Will also show on during times of low sunlight. If issue persists, fill out a maintenance request form. |
| W003 | Grid failure. Incorrect grid parameters. Should resolve itself on when the grid returns to normal but if the issue persists, fill out a maintenance request form. |
| E021 | Inverter relay fail/fault. Restart inverter. If error code remains, fill out a maintenance request form. |
| W010 | Fan fail/fault. Check inverter vents and fans for dust and debris. If the area is clear, fill out a maintenance request form. |
If you experience one of the issues listed with your Aurora or Power-One inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your Aurora or Power-One display is showing.
Fox ESS
Having fitted Fox ESS inverters in the past, at SolarTherm UK we are experienced with their faults and no longer recommend them for our installs. If you have an issue with your Fox ESS inverter, are outside of your warranty and would like expert advice on what happens next, we will be more than happy to help.
| Fault Code | Troubleshooting |
| SPS Fault | Turn off the PV and grid connectors. After 5 minutes reconnect. If issue persists, fill out a maintenance request form. |
| Grid Lost Fault | Check grid connections including wiring, interface, etc. Check grid for known issues such as power cuts. Inverter will reconnect on normal service from the grid. |
| Grid Voltage Fault | Make sure that the grid voltage and frequency complies with standards. Inverter should reconnect on normal service from the grid. If issue persists, fill out a maintenance request form. |
| Isolation Fault | Check the impedance among the PV+, PV- and ground. Impedance should be >1Mohm. If the impedance cannot be detected or is higher than 1Mohm fill out a maintenance request form. |
| OCP | Turn off the PV and grid, reconnect them. |
| Relay Fail | Disconnect PV+ and PV- with DC. After the LCD switches off, reconnect and check again. |
| Comm Lost | Disconnect PV+ and PV-, reconnect after 5 minutes. |
| Over Temp | Check if the environment temperature is over the limit. Check for dirt or debris blocking vents and fans. If issue persists, fill out a maintenance request form. |
If you experience one of the issues listed with your Fox ESS inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please contact us on 01268 552868 for further assistance – have readily available the fault code and what your Fox ESS display is showing.
Fronius
Fronius is a well-known Austrian brand in the solar industry. The advanced technology Fronius inverters offer, provide precise power conversion ensuring maximum efficiency from your solar system. Fronius have been involved in the solar industry since 1992, offering top quality, high end inverters for domestic and commercial properties alike. Fronius inverters come with a standard 5 year manufacturer warranty, which is extended to 10 years on registration of your inverter.
| Error Code | Description | Troubleshooting |
| 326, 327 | Error with fan. | Check inverter vents for dust and debris. If error persists, fill out a maintenance request form. |
| 401 | AC Voltage too high. | Fill out a maintenance request form. |
| 306, 307 | PV output is too low to feed. | This fault will fix itself. It is usually shown at night or when night levels are low. If fault is showing when significant levels of sunlight are showing, fill out a maintenance request form. |
| 417, 418, 419, 420, 421, 425, 426, 427, 428, 431 | Firmware errors. | These fault codes all show a firmware issue. Firmware will need to be updated. Fill out a maintenance request form. |
| 447 | Insulation problem. | This should correct itself within a few hours. If error doesn’t resolve, restart inverter. If issue persists, fill out a maintenance request form. |
| 452 | Communication problem between processors. | Installer needs to attend site to perform maintenance. Fill out a maintenance request form. |
| 502 | Insulation fault on solar panels. | This should correct itself within a few hours. If error doesn’t resolve, restart inverter. If issue persists, fill out a maintenance request form. |
| 509 | No energy has been fed into he grid in the last 24 hours. | Ensure no power outages in the area. If error persists for more than 2 days, fill out a maintenance request form. |
| 517 | No energy has been fed into the grid by MPPT1 in the past 24 hours. | Check nothing is blocking the inverter air openings, if blocked, remove the blockages. The fault should then clear within 5 minutes. If not restart your system. |
| 566 | Arc detector has been deactivated. | Press enter (4th button from the left) and wait 5 minutes for error to clear. |
| 751, 758 | Time errors. | Time and date on inverter needs to be reset. If code does not clear instantly restart the system. |
If you experience one of the issues listed with your Fronius inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your Fronius display is showing.
Growatt
Growatt inverters are reliable, efficient and budget friendly. With a standard 10 year manufacturer warranty and a reasonably priced extended warranty for up to 20 years, these inverters are built to last. Growatt is ranked among the Top 3 inverter suppliers in the world. At SolarTherm UK we have experienced the reliability of Growatt inverters and recommend them to our customers looking for a string inverter.
| Error Code | Description | Troubleshooting |
| Growatt Inverter no AC Connection | No utility grid connected or utility grid power failure | This normally happens during a grid failure. If you still have electricity connected to your property check your AC isolator or circuit breaker. If both are on and the problem persists, fill out a maintenance request form. |
| No Power Output | When the solar inverter shows no power output, your solar panels are inactive. | Check the connection to the solar grid. Check the inverter for error codes or messages. If everything appears as normal, fill out a maintenance request form. |
| Low Power Output | The solar inverter is working but is generating a reduced amount of energy. | Clean your solar panels as per the maintenance guidelines. Schedule a maintenance visit to replace any worn-out or underperforming parts. Monitor the inverters efficiency using the display or online monitoring system. |
| Overheating | When the solar inverter is excessively hot, issues can arise causing performance reduction and safety concerns. | Ensure your inverter is installed in a well ventilated location. Clean your inverter regularly to remove dust and debris from the inverters vents. Where applicable, install shade to protect from direct sunlight. |
| Autotest Failed | Autotest failed | Restart the inverter and the fault will clear. |
| 101 | Communication fault | Turn off the DC switch and make the inverter completely shut down. Turn on the DC switch to see if the error still exists. If the error persists, fill out a maintenance request form. |
| Warning 401 | Inverter communicates with the meter abnormally | Check the meter is on. Check the inverter and meter connection is normal. If issue persists fill, out a maintenance request form. |
If you experience one of the issues listed with your Fronius inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your Fronius display is showing.
LuxPower
The LuxPower hybrid inverter controls both your solar PV panels and your battery (where applicable). At SolarTherm UK we recommend the LuxPower hybrid inverter when your solar installation pairs solar PV panels with a storage battery. The free monitoring program allows you to monitor and program your solar system from your smartphone or tablet using the app, it also allows for remote technical support from LuxPower direct. LuxPower hybrid inverters come with a 12 year manufacturer warranty.
| LCD Display | Description | Troubleshooting |
| 0017 | Internal communication fault | Restart the inverter, if the error persists, fill out a maintenance request form. |
| 01 | Model fault 1 | Reset the model, check that the safety standard switch is in the right place. |
| 12 | EPS short circuit | Check the EPS L and N connection. Disconnect the EPS connector. If the error still persists, fill out a maintenance request form. |
| 16 | Relay fault 1 | Restart the inverter, if the error persists, fill out a maintenance request form. |
| 25 | Temperature over range | Check NTC connection. |
| Warning 00 | Communication failure with battery | Fix communication cable, if the warning persists, fill out a maintenance request form. |
| Warning 17 | AC voltage out of range | Check AC grid voltage |
If you experience one of the issues listed with your LuxPower inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your LuxPower display is showing.
Samil
Samil inverters fill our technical team with fear! SolarTherm UK installed these inverter units for a very short period only. They were a Chinese imported inverter, marketed well to the wholesale market but not quality controlled. They simply did not live up to the claims. This equipment was around circa 2012-2015 and the technical support disappeared quickly also. SolarTherm UK swapped out most of these under our own workmanship warranty when the manufacturer no longer answered their warranty support line or email.
Unfortunately, if you have one of these inverters and it’s still working it would be a surprise. The outcome on this is these inverters are uneconomical and impossible to repair, we would usually offer a newer brand and type of inverter to suit. The quickest and easiest way for us to record this information is to fill in our maintenance request form.
| Fault | Troubleshooting |
| Grid Faults | Wait 5 minutes to see if the grid reverts back to normal working state. Check the grid voltage complies with standards. If issues don’t resolve themselves within 24 hours, fill out a maintenance request form. |
| No Utility | Check there are no known outages or power cuts to your supply. If there are no local faults report the issue using a maintenance request form. |
| Fan Fault | Check the fan and vents to ensure they are clear and free from dust and debris. If the issue persists, fill out a maintenance request form. |
| Relay Failure | Disconnect the PV+, PV- with DC input then reconnect. If this does not resolve the issue, fill out a maintenance request form. |
If you experience one of the issues listed with your Samil inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your Samil display is showing.
SMA Sunny Boy
The SMA Sunny Boy inverter offers high power output and efficient performance at a competitive price. The SMA Sunny Boy inverter comes with a 5 year manufacturer warranty. The SMA Sunny Boy inverter comes with an automatic inverter monitoring service which analyses your system, reports irregularities and minimises downtime.
| Error Code | Description | Troubleshooting |
| 102 | Grid Fault/Overvoltage | Check whether the grid voltage at connection point is in the permissible range. If within permissible range, fill out a maintenance request form. |
| 202 | Grid Fault/Undervoltage | The grid has been disconnected, the AC cable is damaged or the grid voltage is too low. Make sure that the circuit breaker is switched on, check for damage to the AC cable and that it is connected correctly. Fill out a maintenance request form. |
| 3501 | Insulation failure or resistance | Check the PV system for ground faults. If issue persists, fill out a maintenance request form. |
| 3902 | Generator voltage too low | The PV array voltage is too low. Error should resolve when solar radiance has increased. |
| 6002, 6005, 6006, 6305, 6402, 6406, 6415, 6450 | Self diagnosis – check message | Report the fault using the maintenance request form. |
| 8101, 8102 | Communication disturbed | An error has occurred in the internal communication. Fill out a maintenance request form. |
If you experience one of the issues listed with your SMA inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your SMA display is showing.
SolarEdge
At SolarTherm UK we recommend a SolarEdge power optimised system when you have shaded areas or multiple orientations on your roof. The SolarEdge monitoring app allows you to see your electricity generation and each panels efficiency live. They have a 12 year manufacturer warranty as standard, which can be extended to up to 25 years.
SolarEdge error codes are harder to read than some solar inverters. They differ depending on the software version or style of inverter. Fault codes with just a number are version 3.18 or older and fault codes with a mixture of letters and numbers are version 3.19 or newer. The codes also differ depending on whether it is a single phase or three phase inverter. We have listed the most common codes below for a single phase inverter.
| Error Code v3.18 | Error Code v3.19 | Description | Troubleshooting |
| 15 | 2xF | DC voltage too high | Torn off the inverter ON/OFF switch. If after 5 minutes the LCD panel does not show a low safety voltage, check which string is malfunctioning and recheck its connections. |
| 16, 149, 153, 181, 166, 167, 168, 170 | 2×10, 2×95, 2×59, 2xB5,18xA6, 18xA7, 18xA8, A8xAA | Hardware error | Fill out a maintenance request form. |
| 17, 117 | 2×11, 18×75, 2xB6 | Temperature too high | Verify that the inverter has proper clearances. Make sure the heat-sink fins are clean and unobstructed. |
| 147, 150, 151, 12 | 3×11, 2×96, 2×97, 18xC, 18x8E | Arc fault detected | Fill out a maintenance request form. |
| 152 | 2×98 | Arc detector self-test failed | Fill out a maintenance request form. |
| 18×98, 18×99 | Fan failure | Check the fan is clear from dirt and debris. If issue persists, fill out a maintenance request form. | |
| 2xC5 | Rapid shutdown test failed | Check safe VDC voltage and if it doesn’t drop below 30V check string voltage. Set rapid shutdown functionality. Check inverter for internal damage. If issue persists, fill out a maintenance request form. |
If you experience one of the issues listed with your SolarEdge inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your SolarEdge display is showing.
SolaX
SolaX has been in the solar industry for over 20 years, and what sets them above other inverter brands is their focus on inverters – meaning they often lead the way on new technology, ideas and design. SolaX inverters come with a 5 year manufacturer warranty as standard on most models, although newer models are now including a longer warranty.
| Inverter Screen | Description | Troubleshooting |
| Sample Fault | Detection circuit fault. | The detection reference circuit in the inverter is operating abnormally. Fill out a maintenance request form. |
| Fan1 Fault/Fan2 Fault | Fan device fault. | The internal fan within the inverter is operating outside normal parameters. Restart your inverter. Check for visible dust or debris blocking the fan from spinning. If the issue persists, fill out a maintenance request form. |
| EPS Relay fault | EPS relay fault. | Disconnect the panel array and battery by switching off the DC isolator and battery isolator switches. Shut-down the inverter and then reconnect. If this doesn’t resolve the error, fill out a maintenance request form. |
| Grid Lost Fault | No grid connection. | The system will automatically reconnect once the grid returns to normal. If your inverter doesn’t reconnect after a power cut contact us for further advice. |
| Grid Volt Fault | Abnormal grid voltage. | The grid voltage is out of range. Your inverter will automatically reconnect once the grid returns to normal. |
| Isolation Fault | Isolation fault. | Check the connection of the inverter. If the fault code doesn’t disappear, fill out a maintenance report form. |
If you experience one of the issues listed with your SolaX inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your SolaX display is showing.
Solis
The Solis brand is a long established Chinese solar inverter manufacturer, ranked as the 3rd largest manufacturer in the world. Seen as a entry -level inverter due to their low cost, Solis is a popular inverter with excellent features. With a 5 year warranty as standard, extendable up to 20 years.
| Error Code | Description | Troubleshooting |
| No information (blank screen) | Input voltage low/missing. Polarity reversed. Main board damaged. | Test: DC switch OFF Check PV connections, polarity, check voltage >120V (single phase). If DC voltage is 0 inverter needs replacing. Fill out a maintenance request form. |
| OV-G-V: Over Grid Voltage | Inverter detects grid voltage as too high. | Fill out a maintenance request form. |
| NO-GRID | Inverter does not detect the grid. | Check LCD reading – may be a bad measurement circuit. Check grid standard. If issue persists, fill out a maintenance request form as the inverter may need replacing. |
| ARC-FAULT | Inverter detects arc in DC circuit. | Inspect installation – check cables, junction boxes and cable connections. Reset inverter. If issue persists, fill out a maintenance request form. |
| LCD show initiating all the time | Can not start-up. | Check if the connector on the main board or power board are fixed. If issue persists, fill out a maintenance request form. |
If you experience one of the issues listed with your Solis inverter, please follow the steps above and if the issue persists or your issue isn’t listed, please fill out a maintenance request form or contact us on 01268 552868 for further assistance – have readily available the fault code and what your Solis display is showing.
While inverter fault codes can initially seem daunting, many issues can be resolved with simple checks or a system restart. However, persistent faults or unfamiliar codes may indicate a deeper problem requiring professional intervention. At SolarTherm UK, we pride ourselves on offering honest advice, expert technical support, and reliable solutions tailored to your solar system. Whether you need help diagnosing an issue, require replacement parts, or are considering an inverter upgrade, our team is here to help.
To speak with our experienced technical team, please fill out a maintenance request form or contact us directly on 01268 552868. Having your fault code and inverter display message ready will help us assist you faster and more efficiently.
Solartherm UK, and its parent company Silvercrest Energy Group Ltd experience less than favourable lead times when waiting for warranty claims, hardware updates and part replacements, the current lead times for repairs can be 4-6 weeks but can be as quickly as a matter of days. We have a designated team who can always be contacted easily at [email protected] who are chasing manufacturers daily. Rest assured, the team at SolarTherm UK will be with you as soon as we have the replacement parts at your earliest convenience.
With decades of experience in the solar industry, you can trust SolarTherm UK to keep your solar system running at its best.
