NMS Inverter Common Fault Codes Interpretation: E01-E50 Troubleshooting Guide

1. Grid-Related Faults (E01-E10)

E01: Grid Voltage Too Low

1. Fault Meaning: The detected grid voltage is lower than the inverter’s minimum grid-connected voltage threshold (single-phase: <170V; three-phase: <323V).

2. Possible Causes: Rural power grid voltage fluctuation during peak load periods; loose AC wiring terminals; too thin or too long AC cables leading to voltage drop; grid failure in remote rural areas.

3. Troubleshooting Steps:        - Use a multimeter to measure the grid voltage at the inverter’s AC output terminal; wait for grid recovery if the voltage is abnormally low.        - Check AC wiring for looseness or corrosion (common in humid rural environments) and re-tighten terminals.        - Replace with thicker AC cables or shorten cable length to reduce voltage loss; avoid overloading the local grid.

E02: Grid Voltage Too High

1. Fault Meaning: The detected grid voltage exceeds the inverter’s maximum grid-connected voltage threshold (single-phase: >264V; three-phase: >456V).

2. Possible Causes: Rural grid voltage surge during low load periods; excessive grid impedance leading to voltage rise when surplus PV power is fed into the grid; incorrect inverter grid voltage parameter setting.

3. Troubleshooting Steps:        - Disconnect the inverter from the grid, restart after 30 minutes, and observe if the fault is eliminated.        - Adjust PV system output power or increase local load consumption to reduce surplus power feeding into the grid.        - Confirm that the inverter’s grid voltage parameter matches the local rural grid standard (220V/380V); modify parameters via the mobile app if necessary.

E03: Grid Frequency Abnormality

1. Fault Meaning: The grid frequency is outside the inverter’s adaptive range (50Hz±2Hz).

2. Possible Causes: Rural small hydropower or diesel generator grid connection causing frequency fluctuation; grid dispatching adjustment; inverter frequency detection circuit malfunction.

3. Troubleshooting Steps:        - Measure grid frequency with a frequency meter; wait for grid stabilization if the frequency is abnormal.        - Disconnect other grid-connected devices (such as diesel generators) temporarily to avoid mutual interference.        - If the grid frequency is normal but the fault persists, the inverter’s detection circuit may be faulty; contact after-sales service.

E04-E10: Other Grid-Related Faults

• E04: Anti-islanding Protection Triggered. Check if the local grid is powered off; restart the inverter after grid recovery. Ensure the anti-islanding function is enabled (compliant with GB/T 19939 standard).

• E05-E06: Grid Phase Sequence Error/Phase Loss. For three-phase inverters, check if AC three-phase wiring is correct and tight; repair damaged cables in time (common in farmland environments with rodent bites).

• E07-E10: Reactive Power Adjustment Failure. Enable reactive power compensation function via the cloud platform; clean the inverter’s cooling system to avoid overheating affecting control circuit operation.

2. DC Side Faults (E11-E25)

E11: PV Input Voltage Too Low

1. Fault Meaning: The PV array input voltage is lower than the inverter’s minimum startup voltage (usually <100V).

2. Possible Causes: Insufficient sunlight (morning fog, shading by crops/trees in rural areas); too few PV panel series; loose DC connections; damaged PV panels.

3. Troubleshooting Steps:        - Wait for sufficient sunlight or remove shading objects (trim overgrown branches, clean panel surfaces).        - Check DC wiring terminals for looseness or oxidation; re-tighten and apply anti-corrosion grease (adapt to humid rural environments).        - Measure the open-circuit voltage of each PV string; ensure the series number meets the inverter’s voltage requirement.

E12: PV Input Voltage Too High

1. Fault Meaning: The PV array input voltage exceeds the inverter’s maximum DC voltage (usually >500V for single-phase models).

2. Possible Causes: Too many PV panel series, leading to excessive voltage in low-temperature rural environments; PV string short circuit causing voltage surge.

3. Troubleshooting Steps:        - Reduce the number of PV panels in series (suggested string voltage: 350-400V for single-phase models) to adapt to low-temperature voltage rise characteristics.        - Disconnect each PV string separately to locate the short-circuited string; replace damaged panels or cables.        - Avoid installing PV arrays in areas with extreme low temperatures without voltage adjustment.

E13: PV Input Current Overload

1. Fault Meaning: The PV input current exceeds the inverter’s maximum DC input current.

2. Possible Causes: High sunlight intensity leading to PV current surge; parallel PV strings with mismatched current; DC cable short circuit.

3. Troubleshooting Steps:        - Check if the PV string current matches the inverter’s DC input rating; reduce parallel strings if overloaded.        - Inspect DC cables for insulation damage (prone to dust and moisture in rural areas) and replace if short-circuited.        - Utilize the inverter’s 20% power redundancy function to avoid overload under strong light.

E14-E25: Other DC Side Faults

• E14-E16: PV Polarity Reverse/Short Circuit. Check DC wiring polarity (avoid reverse connection during rural on-site installation); use a multimeter to locate short-circuited points.

• E17-E20: Insulation Resistance Too Low. Disconnect PV input and measure the resistance between PV+/- and ground (should be >500KΩ); clean PV panels and wiring boxes to remove moisture and dirt.

• E21-E25: MPPT Module Malfunction. Restart the inverter; if the fault persists, check the dual MPPT inputs (for NMS models) for uneven load distribution; contact after-sales to replace the MPPT module.

3. Hardware & Overheating Faults (E26-E40)

E26: Inverter Overheating

1. Fault Meaning: The inverter’s internal temperature exceeds the protection threshold (usually >60°C).

2. Possible Causes: Direct sunlight exposure in rural areas; blocked cooling vents by dust; poor ventilation around the inverter.

3. Troubleshooting Steps:        - Install a sunshade for the inverter; avoid placing it in enclosed spaces (such as farm sheds) without ventilation.        - Clean cooling vents and fans regularly to remove dust and agricultural residues.        - Ensure the inverter is installed vertically to facilitate heat dissipation (adapt to rural roof and farm shed installations).

E27-E30: Power Module Faults

E31-E40: Other Hardware Faults

• E31-E33: Fan Malfunction. Replace the fan if it is stuck or noisy (NMS modular design allows easy fan replacement); clean fan blades regularly.

• E34-E37: Control Circuit Fault. Reset the inverter to factory settings via the mobile app; if the fault remains, the main control board is faulty, requiring after-sales repair.

• E38-E40: Battery Fault (Off-Grid Models). Check battery connection and BMS communication; avoid overcharging/discharging; replace aging batteries.

4. Communication & System Faults (E41-E50)

E41: WiFi/4G Communication Failure

1. Fault Meaning: The inverter fails to connect to the mobile app or cloud platform.

2. Possible Causes: Weak rural network signal; incorrect WiFi/4G parameter setting; SIM card failure (for 4G models).

3. Troubleshooting Steps:        - Move the inverter’s antenna to a location with better signal (avoid shielding by rural buildings); replace the SIM card if expired.        - Reconfigure network parameters via the inverter’s local display or mobile app; ensure the "one-send dual-receive" function is enabled.        - Use wired communication (RS485) for collective projects in areas with poor wireless signals.

E42-E50: Other System Faults

• E42-E45: Data Storage Failure. Clear historical data via the cloud platform; if the fault persists, replace the internal storage module.

• E46-E48: Load Mismatch. Adjust the connected load to match the inverter’s output power; avoid starting large inductive loads (such as irrigation pumps) simultaneously.

• E49-E50: System Self-Check Failure. Restart the inverter and perform a manual self-check via the app; contact after-sales for comprehensive maintenance if the fault recurs.

5. General Troubleshooting Tips & Preventive Measures

5.1 General Tips

• For most transient faults (such as voltage fluctuation), disconnect DC/AC power, wait 30 minutes, and restart the inverter.

• Use the NMS inverter’s I-V curve diagnosis function to locate PV panel faults within 5 minutes, reducing on-site inspection time.

• Keep maintenance records for rural collective projects, including fault codes, handling methods, and replacement components.

5.2 Preventive Measures

• Clean PV panels and inverters quarterly to remove dust, agricultural residues, and bird droppings.

• Inspect wiring terminals before and after extreme weather (thunderstorms, low temperatures) to ensure tightness and insulation.

• Update the inverter’s firmware regularly via the cloud platform to optimize fault protection performance.

• Train rural users on basic operation and fault recognition to avoid improper operation leading to faults.

Conclusion