Common Solar Inverter Errors Explained
As a solar technician and installer, one of the most common challenges I face on-site is dealing with solar inverter errors. Since the inverter is the heart of any solar energy system—responsible for converting DC electricity from solar panels into usable AC power—any fault here can disrupt the entire system.
Over the years, I’ve worked on different brands of inverters such as SMA, Huawei, Fronius, Growatt, Schneider, and Victron. While error codes may differ slightly from brand to brand, I’ve noticed that most issues fall into similar categories: grid-related errors, panel/input errors, temperature faults, communication issues, and internal hardware failures.
In this guide, I’ll share how I personally diagnose and fix the most common solar inverter errors, along with a detailed table of error codes and solutions that can help installers and technicians on the field.
Step 1: Safety First
Before I touch any inverter, I always:
- Switch off the DC isolator from the solar panels.
- Switch off the AC isolator to disconnect from the grid.
- Put on my PPE (gloves, tester, safety shoes).
⚠️ Tip: Never attempt to fix a solar inverter error while the system is live unless you’re performing diagnostics with a multimeter.
Step 2: Understand the Error Category
Most solar inverter errors fall under:
- Grid Errors – Issues with voltage, frequency, or grid instability.
- DC Input Errors – Low PV voltage, reversed polarity, or string mismatch.
- Overheating/Temperature Errors – Caused by poor ventilation or dust.
- Communication Errors – RS485, Wi-Fi, or monitoring issues.
- Internal Hardware Errors – Faulty relays, capacitors, or firmware.
Step 3: Use Error Codes as a Guide
Every inverter displays an error code or message. Some show this on the LCD screen, others via LEDs, and some through mobile apps. Once I see the code, I check the manufacturer’s manual. However, I’ve compiled a general reference table that applies to most inverters.
Common Solar Inverter Error Codes and Solutions
| Error Code / Message | Possible Cause | How I Fix It (Step-by-Step Solution) |
|---|---|---|
| Grid Over Voltage (OVG) | Grid voltage too high (> 260V AC in single-phase systems) | 1. Test grid voltage with a multimeter. 2. If it’s the utility, I advise client to contact the power provider. 3. If local wiring is faulty, I check neutral and earthing. |
| Grid Under Voltage (UVG) | Grid voltage too low (< 180V AC) | 1. Confirm grid supply. 2. Check for loose or undersized cables. 3. If persistent, install a stabilizer or AVR. |
| Grid Frequency Error | Grid frequency outside 49–51 Hz range | Usually a utility issue. I wait until grid stabilizes. If frequent, I recommend hybrid inverter with frequency tolerance. |
| No Grid / Grid Lost | Grid disconnected or phase missing | 1. Check if utility power is present. 2. Inspect fuses, breakers, and AC isolators. |
| DC Bus Over Voltage | Excess solar voltage beyond inverter rating | 1. Verify string configuration. 2. Measure Voc of panels (shouldn’t exceed max inverter input). 3. Reconfigure if too many panels in series. |
| DC Low Input / Low PV Voltage | Solar panels not producing enough voltage | 1. Test string voltage with multimeter. 2. Check shading, dirt, or wrong connections. 3. Reconnect strings properly. |
| PV Isolation Fault / Ground Fault | Current leakage to ground | 1. Insulation resistance test with megger. 2. Inspect damaged cables, connectors, or water ingress. 3. Replace faulty panels or wiring. |
| Polarity Error (Reverse DC) | Positive and negative wires swapped | 1. Disconnect PV isolator. 2. Correct polarity. 3. Restart inverter. |
| Over Temperature | Inverter running too hot | 1. Check ventilation, clear dust, and unblock fans. 2. If ambient temp is high, install inverter in a shaded/ventilated area. |
| Relay Check Fail | Internal relay stuck or faulty | 1. Restart inverter. 2. If persists, relay board may need replacement. |
| Communication Failure | RS485/Wi-Fi module not communicating | 1. Check cables, ports, or Wi-Fi dongle. 2. Restart communication device. 3. Update monitoring app. |
| Isolation Resistance Low | Water ingress in panels or cables | 1. Test strings individually with insulation tester. 2. Replace faulty string. 3. Seal connectors properly. |
| Internal Error / Hardware Failure | Faulty inverter components | 1. Restart inverter. 2. Update firmware. 3. If error persists, replace board or send inverter to manufacturer. |
Step 4: When to Repair vs. Replace
In my experience:
- Minor issues (loose connections, wiring, dust, shading) → I fix on-site.
- Hardware faults (relay board, capacitors, IGBTs) → I replace the faulty module if spare parts are available.
- Severe internal damage → It’s usually cheaper and faster to replace the entire inverter, especially for smaller residential systems.
Step 5: Preventing Future Solar Inverter Errors
I always advise my clients:
- Install the inverter in a cool, dry, and well-ventilated area.
- Ensure correct PV string configuration during installation.
- Use quality surge protectors (AC & DC SPD).
- Perform regular maintenance – cleaning, tightening, and inspection.
- Update firmware/software when recommended by the manufacturer.
Final Thoughts
Diagnosing and fixing solar inverter errors is all about understanding the error codes, checking the basic inputs, and knowing when to repair or replace. Over the years, I’ve realized that most issues can be solved with simple checks before calling in the manufacturer.
If you’re a fellow solar installer or technician, always remember: document every error you encounter—it will help you build experience and troubleshoot faster in the future.
