Solis Inverter Low or No PV Generation: Diagnosis and Fixes

Key Takeaways

• Low or no PV generation on a Solis S5-EH1P-L inverter is often caused by grid instability, PV array issues, or internal inverter protection mechanisms.
• The first step in troubleshooting is always to check the inverter's LCD screen for active fault codes.
• Never open the inverter casing. Wait at least 5 minutes after disconnecting all power sources (PV, grid, battery) before touching any internal components.
• If the inverter displays internal hardware faults, persistent grid issues, or PV ground faults, contact a qualified technician.

Why is my Solis inverter showing low or no PV generation?

If your Solis S5-EH1P-L hybrid inverter is producing less power than expected or no power at all, the most common causes are issues with the grid connection, problems within the PV array, or the inverter limiting its output due to internal or external conditions. Start by checking the inverter's LCD display for any specific fault codes, as these will guide your troubleshooting.

Diagnosis

Follow these steps to diagnose why your Solis inverter is experiencing low or no PV generation.

1. Check the Inverter Display for Fault Codes:

• • Observation: The inverter's LCD screen shows a fault code (e.g., LmtByFreq, OV-DC01, NO-Grid).
  • Meaning: Specific codes pinpoint the exact issue. Refer to the "Cause/fix table" below for detailed explanations and initial troubleshooting steps.
  • Action: Note the code and proceed to the relevant section in the table.

2. Inspect PV Array Connections and Condition:

• • Observation: No fault codes related to PV input, but generation is low. Visually inspect solar panels and wiring.
  • Meaning: Damaged panels, shading, loose connections, or ground faults can reduce PV input.
  • Action: Check for visible damage, excessive shading, or loose PV cable connections. If you suspect a PV ground fault (e.g., PV ISO-PRO01 or PV ISO-PRO02), do not attempt to fix it yourself.

3. Verify Grid Connection and Stability:

• • Observation: Inverter displays grid-related fault codes (e.g., NO-Grid, OV-G-V04, UN-G-F01) or generation stops when the grid is unstable.
  • Meaning: The inverter disconnects from the grid or limits output if grid voltage or frequency is outside acceptable ranges, as required by local safety regulations.
  • Action: Check your main electrical panel for tripped breakers. Confirm with your utility provider if there are known grid issues in your area.

4. Check Environmental Factors:

• • Observation: Inverter displays LmtByTemp or UN-TEM fault codes, or the inverter feels excessively hot/cold.
  • Meaning: The inverter may limit output due to over-temperature protection or cease operation in extremely low temperatures.
  • Action: Ensure the inverter's ventilation openings are clear and not obstructed. Verify that the installation environment meets the recommended temperature ranges. The surface temperature of the inverter can reach up to 75℃ (167℉) during operation.

5. Review Inverter Settings:

• • Observation: Inverter displays LmtByEPM, LmtByDRM, LmtByVg, or LmtByVar.
  • Meaning: These codes indicate that the inverter's output is being intentionally limited by an external power meter (EPM), Demand Response Management (DRM) function, or grid-support modes (Volt-Watt/Volt-Var).
  • Action: If these settings were not intentionally configured, consult your installer or technician. Accessing advanced settings requires a password (0010) and should only be done by authorized personnel, as improper operation may result in abnormal results and damage to the inverter. Unauthorized access may void the warranty.

Cause/fix table

This table outlines common symptoms, their likely causes, and initial troubleshooting steps for low or no PV generation on your Solis S5-EH1P-L inverter.

PV-side checks vs. Grid-side checks vs. Inverter-side checks

When your Solis S5-EH1P-L inverter is generating low or no power, the problem can originate from the solar panels and their connections to the inverter (PV-side), the electrical grid (Grid-side), or the inverter itself (Inverter-side).

PV-side checks

These checks focus on the solar panels and their connections to the inverter.

• Visual Inspection: Look for physical damage to panels, heavy shading, or debris.
• Connection Integrity: Ensure all DC cables from the PV array are securely connected to the inverter's PV input terminals. Loose connections can lead to reduced power or intermittent generation.
• PV Input Overvoltage: If the inverter displays OV-DC01 or OV-DC02, the voltage from the PV string is too high. This can happen if too many panels are wired in series for the inverter's specifications. Do NOT attempt to measure or alter PV array wiring yourself, as high DC voltages are present and can be lethal. This requires a qualified technician to assess the PV array design and connections.
• PV Ground Faults: Faults like PV ISO-PRO01 (PV negative ground fault) or PV ISO-PRO02 (PV positive ground fault) indicate insulation issues or damaged cables in the PV strings. These are serious safety concerns. A PV ISO-PRO fault indicates a serious electrical hazard. Immediately isolate the PV array using the DC switch, but ONLY if the DC current is below 0.5A. If the current is above 0.5A, wait for solar irradiance to reduce until the current decreases to below 0.5A before operating the DC switch. Do NOT attempt to troubleshoot or fix this yourself. High DC voltages are present. This requires immediate attention from a qualified technician to prevent electrical hazards and avoid voiding your warranty. Contact a professional.

Grid-side checks

These checks relate to the stability and connection of the utility grid. The inverter needs a stable grid connection to operate in grid-tied mode and export power.

• No Grid Detected: A NO-Grid fault means the inverter cannot detect the utility grid. Check your main AC breaker and any external AC disconnects. Confirm with your utility provider if there's a power outage or instability in your area.
• Grid Voltage/Frequency Issues: Codes such as OV-G-V04 (Grid voltage exceeds upper voltage range), UN-G-F01 (Grid frequency exceeds lower frequency range), or G-PHASE (Unbalanced grid voltage) indicate that the grid parameters are outside the inverter's operational limits. The inverter will disconnect or limit output to protect itself and the grid. These issues usually require intervention from the utility company or an electrician to verify grid quality.
• Grid Current Tracking Failure: An IGFOL-F fault suggests the inverter is having trouble synchronizing with the grid's current. This may point to grid instability or an internal inverter issue related to grid interaction.

Inverter-side checks

These checks pertain to the inverter's internal operation, settings, and components.

• Output Limiting: Codes like LmtByEPM, LmtByDRM, LmtByTemp, LmtByFreq, LmtByVg, or LmtByVar indicate that the inverter is intentionally limiting its output. This can be due to external control, internal over-temperature protection, or grid-support functions. LmtByTemp is a normal protective measure; ensure adequate ventilation. Other LmtBy codes may require checking advanced settings, which should only be done by authorized technicians.
• Internal Faults: Codes such as DC-INTF. (DC hardware overcurrent), RelayChk-FAIL (Relay failure), DSP-B-FAULT (Master-slave DSP communication abnormal), or 12Power-FAULT (12V undervoltage failure) point to internal hardware malfunctions. These are NOT user-serviceable. Do NOT open the inverter casing. High voltages are present, and capacitors can store dangerous energy for several minutes after power disconnection. Opening the inverter without authorization will void the warranty. These faults require a qualified technician.
• Fan Malfunction: A Fan Alarm indicates an issue with the inverter's cooling fan. If the fan is externally accessible, visually check for obstructions. Do NOT open the inverter casing or attempt to physically manipulate the fan. Internal fan issues are NOT user-serviceable. High voltages are present, and capacitors can store dangerous energy for several minutes after power disconnection. Opening the inverter without authorization will void the warranty. This requires diagnosis and repair by a qualified and authorized service technician.

Safety

Working with solar inverters and electrical systems carries significant risks. Always prioritize safety.

• Qualified Personnel: Operations must be accomplished by a licensed technician or Solis authorized person.
• Electrical Standards: Electrical installations must be done in accordance with local and national electrical safety standards.
• Personal Protective Equipment: Always wear technicians’ gloves during the whole process in case of any electrical hazards.
• Internal Components: Do not touch any inner live parts until 5 minutes after disconnection from the utility grid and the PV input. There is a risk of electric shock from energy stored in capacitors. Do not remove the cover for 5 minutes after disconnecting all power sources.
• Hot Surfaces: The surface temperature of the inverter can reach up to 75℃ (167℉). To avoid risk of burns, do not touch the surface of the inverter while it’s operating.
• PV Array Connection: Do not connect PV array positive (+) or negative (-) to ground, as it could cause serious damage to the inverter.
• DC Reverse Connection: If DC inputs are accidentally reversely connected or the inverter is faulty, it is NOT allowed to turn off the DC switch immediately if the current is above 0.5A. Wait for the solar irradiance to reduce until the current decreases to below 0.5A. Only after the current is below 0.5A are you allowed to turn off the DC switches and disconnect the PV strings. Damages due to wrong operations (DC reverse connection) are not covered in the device warranty.

When to call a technician instead

While some basic troubleshooting can be performed, many issues with the Solis S5-EH1P-L inverter require professional intervention. You should call a qualified technician if:

• Persistent Fault Codes: The inverter displays internal fault codes (e.g., DC-INTF., RelayChk-FAIL, DSP-B-FAULT, 12Power-FAULT) that do not clear after a system restart.
• PV Ground Faults: Any PV ISO-PRO fault (PV negative or positive ground fault) indicates a serious electrical hazard within your solar array.
• Grid Issues Persist: If grid-related faults (NO-Grid, OV-G-V04, UN-G-F01, G-PHASE) continue even after verifying your main breaker and confirming no utility outages.
• Physical Damage: You observe physical damage to the inverter, wiring, or solar panels.
• Advanced Settings: You need to change settings in the "Advanced Settings" menu (password 0010). This function is for authorized technicians only, and improper operation may result in abnormal results, damage to the inverter, and may void the warranty.
• Warranty Concerns: If you suspect an issue that may be covered under warranty, but requires opening the inverter or complex diagnostics. Removing the cover without authorization may void the warranty.