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Fault code reference · AlphaESS SMILE inverter & battery

AlphaESS Error Code Reference

Every AlphaESS SMILE inverter error code and battery alarm — the numeric code, what triggered it, and whether you need an engineer or can resolve it yourself. Look up your code below or browse by system area.

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Sourced from official AlphaESS SMILE5 maintenance manual Covers SMILE5, SMILE-S5, and SMILE-BAT series Includes inverter errors (100xxx) and system alarms (110xxx)

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Grid / AC Solar / PV Battery / BMS Inverter / DC Backup / UPS Safety System
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If your AlphaESS inverter is flashing red or showing a numeric error code and you're unsure what to do next, a remote diagnostic identifies the root cause from your Alpha Cloud data — typically within 30 minutes.

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How to find your error code. On the inverter LCD, press ENT → Status to view active faults. In Alpha Cloud (cloud.alphaess.com), open My System and check alarm history. AlphaESS uses numeric codes — 100xxx codes are inverter errors (the system has stopped or limited operation), while 110xxx codes are alarms (warnings that may self-clear). Note the full number before searching this index.
Grid & AC faults

Fault codes triggered by mains supply conditions — voltage deviations, frequency shifts, grid loss, and relay failures. The inverter disconnects from the grid automatically when these protections activate.

100010 — Grid_relay_fault Inverter error — grid relay
The grid relay inside the inverter has failed its self-test. If it occurs occasionally due to a short-term grid abnormality, the inverter recovers automatically. If it recurs frequently and the grid supply is normal, the internal relay may be damaged — contact AlphaESS support or book a diagnostic.
110004 — dc_power_alarm Alarm — grid overvoltage derating
The inverter has entered a derating state due to high grid voltage. Check the grid voltage reading on the LCD or Alpha Cloud — if it is consistently above 253V, the issue is with the mains supply. Contact your DNO. Confirm the Level 1 overvoltage protection threshold with AlphaESS support if needed.
110021 — Grid Loss Alarm Alarm — no grid detected
No mains supply detected. The inverter will resume automatically once the grid returns. If the alarm persists, confirm the AC breaker is on, the AC cable connections at the inverter are tight, and the consumer unit breaker for the solar circuit has not tripped. If the mains supply is present but the alarm continues, the inverter AC input circuit may be faulty.
110022 — Grid Volt Alarm Alarm — grid voltage out of range
Grid voltage is outside the acceptable operating window. Check the grid cable connection is secure. Restart the inverter and monitor whether the alarm returns. If the grid supply is consistently high or low, contact your DNO — the inverter is protecting itself correctly. Grid overvoltage guide →
110023 — Grid Freq Alarm Alarm — grid frequency out of range
Grid frequency has drifted outside the permitted range (typically 47.5–52Hz). The inverter disconnects as required by G98/G99 protection settings and will resume when the grid stabilises. If the alarm recurs frequently, contact your DNO. After obtaining permission, AlphaESS support can adjust the inverter grid protection parameters via the app.
110024 — 10min Grid Volt Alarm Alarm — sustained voltage deviation
The 10-minute sliding average of grid voltage has exceeded the allowable range. This is a more persistent overvoltage or undervoltage condition than a momentary spike. Check the grid voltage and the sliding average voltage protection settings in the inverter configuration.
110027 — LN Reverse Alarm ⚠ Wiring fault — do not ignore
The mains live and neutral wires are reversed at the inverter AC connection. This is a wiring fault that must be corrected by a qualified electrician — do not operate the system until the L/N polarity is corrected at the AC terminal block.
110059 — grid waveform abnormal alarm Alarm — waveform distortion
The grid AC waveform is distorted beyond acceptable limits. This is typically a short-term grid supply anomaly and the inverter will resume automatically. If it occurs frequently, contact your DNO and ask AlphaESS support to review the grid protection parameter settings via the app.
Solar / PV faults

Codes related to the DC input from solar panels — insulation resistance, string polarity, overvoltage from too many panels in series, and input detection failures.

100007 — Insulation_fault Inverter error — insulation resistance
PV string insulation resistance is below the safe threshold. Often caused by moisture on panel cables or junctions — check whether conditions are wet or humid. If the alarm occurs in dry weather, disconnect strings one at a time and power on to isolate the faulty string. Use a megohmmeter to test each string (normal reading is in the megohm range). Persistent insulation faults indicate degraded cable insulation or a damaged panel junction box.
100012 — PV_Reverse ⚠ Polarity reversed — do not touch DC
PV string cables are connected with reversed polarity. The positive and negative DC connectors are swapped. Switch off the PV isolator and do not touch DC cabling — a qualified engineer must reconnect the cables in the correct orientation.
110014 — Pv over voltage Alarm — PV string voltage too high
The open-circuit voltage of the PV string exceeds the maximum MPPT input voltage. Calculate the maximum open-circuit voltage at the lowest expected local temperature and compare it with the MPPT rating. If the string has too many panels in series, one or more panels will need to be removed or the string reconfigured.
110048 — No Pv Input Alarm Alarm — no solar generation
No PV input detected. If this occurs in weak light (early morning, dusk, heavy cloud) it is normal — the string voltage is simply too low to activate the MPPT tracker. If it occurs in good light, check for a short circuit or open circuit in the panel string connections. Verify the PV isolator is switched on and the string insulation resistance is adequate.
110049 — Input Power Limit Alarm Alarm — PV input power limited
PV input power has reached the inverter's maximum input capacity and is being clipped. This is normal behaviour in peak generation conditions — no action required. The inverter limits input power to protect its components.
Battery & BMS faults

Codes from the battery management system and the inverter's battery interface — covering overvoltage protection, undervoltage shutdown, communication loss, and overcurrent events during charging or discharging.

100025 — BAT_OVP Inverter error — battery overvoltage
Battery voltage has exceeded the safe upper limit. During initial installation, confirm the battery voltage is within the allowable range for the inverter model. If this occurs during normal operation, it may indicate a charging fault or BMS communication anomaly — check that battery wiring is secure and BMS communication is intact. A loose connection can cause voltage spikes that trigger this protection.
100026 — BAT_UVP Inverter error — battery undervoltage
Battery voltage has dropped below the minimum safe threshold. Confirm the battery voltage is within the allowable range and that both the inverter breaker and the battery switch are closed and on. If the alarm occurs during operation, check whether the breaker has tripped and whether the battery BMS is reporting any alarms of its own.
100027 — Battery_lose Inverter error — battery not detected
The inverter cannot detect the battery. Check that the battery DC wiring is connected correctly and securely, the DC switch is closed, and the BMS communication cable (RS485 or CAN) is in place. If the battery is powered on and the connections are correct, the BMS may have entered a lockout state — power cycle both the inverter and battery.
100030 — BAT1_discharge_OCP Inverter error — battery overcurrent
Battery discharge current has exceeded the protection limit. If the battery is over-discharged, reduce the backup load connected to the inverter and restart. Wait five minutes for the fault to automatically clear. If it persists, the battery or inverter may have a hardware issue requiring diagnosis.
110005 — Battery stops running alarm Alarm — battery shutdown
The battery has stopped operating due to a shutdown command. Contact AlphaESS support to restart the inverter and check whether it recovers. If the alarm clears after a restart but returns, unplug the communication module and confirm whether the alarm clears — if so, the communication module may need replacing.
Inverter & DC bus faults

Internal inverter errors related to the DC bus, output stage, and power electronics. Many of these recover automatically from transient grid disturbances — persistent occurrences indicate a hardware fault requiring professional diagnosis.

100005 — BUS_OVP1 Inverter error — DC bus overvoltage
Internal DC bus voltage has exceeded the safe limit. An occasional occurrence caused by a grid transient will recover automatically. If it persists, the inverter's internal voltage regulation is faulty — contact AlphaESS support for further diagnosis.
100038 — Output_DC_over_current Inverter error — DC output overcurrent
DC output current has exceeded the protection threshold. A transient grid anomaly can trigger this — the inverter should recover automatically. If it continues to appear and the inverter cannot generate power normally, the output stage may be damaged. Contact AlphaESS support.
100041 — Output_DC_over_voltage Inverter error — DC output overvoltage
DC output voltage has exceeded the protection threshold. An occasional occurrence recovers automatically. If it persists and the inverter cannot generate power, the internal circuitry may be faulty — contact AlphaESS support for further investigation.
100046 — DC_Input_Disturbance Inverter error — DC input disruption
Disturbance detected on the DC input from the PV array. Occasional occurrences from grid transients recover automatically. If it persists, check DC cable connections and PV string integrity. Contact AlphaESS support if the fault continues after verification.
100054 — Dc_bus_undervolt Inverter error — DC bus undervoltage
Internal DC bus voltage has dropped below the operating minimum. An occasional occurrence will self-recover. Persistent faults indicate the inverter's internal power supply or voltage regulation has failed — contact AlphaESS support.
100166 — inverter circuit abnormal Inverter error — internal circuit fault
The inverter circuit has failed to start normally or an internal flag is set. Try restarting the inverter. If it does not recover, contact AlphaESS support to remotely upgrade the firmware. As a last resort, fully power off the inverter (all breakers off, wait 5 minutes) and restart. If the fault still persists, the inverter requires professional inspection.
100167 — boost circuit abnormal Inverter error — boost converter fault
The inverter's boost converter circuit is not functioning correctly. Contact AlphaESS support to try a remote firmware upgrade. If the inverter does not recover, fully power off, wait 5 minutes, and restart. Persistent faults indicate a hardware issue requiring professional repair.
110040 — Inv Volt Low Alarm Alarm — inverter voltage low
Low component voltage detected inside the inverter. In weak light conditions (dawn, dusk, heavy rain) this is normal and will clear when irradiance improves. If it occurs in good sunlight, check for a short circuit or open circuit in the PV string connections.
Backup / UPS faults

Faults related to the backup (UPS) output — the secondary AC output that powers essential loads during a grid outage. Overload and overvoltage protection events on this circuit.

100042 — Output_short Inverter error — output short circuit
A short circuit has been detected on the backup output. Disconnect the backup load and restart the inverter. If the fault clears, the issue is with the connected appliance or the backup wiring — inspect the backup circuit for damage. If the fault cannot be cleared, the inverter output stage may be damaged.
100043 — Output_overload Inverter error — backup overloaded
The load connected to the backup output exceeds the inverter's UPS power rating. Check which appliances are connected to the backup circuit and remove high-draw items such as kettles, heaters, or electric ovens. Reduce the load, then restart the inverter or wait five minutes for the fault to auto-clear. If the fault persists after reducing the load, disconnect the backup load entirely and restart.
100052 — Backup_ovp Inverter error — backup overvoltage
Overvoltage detected on the backup output. An occasional occurrence will recover automatically. If persistent, the inverter's backup output voltage regulation may be faulty — contact AlphaESS support for further diagnosis.
110050 — Output Power Limit Alarm Alarm — output power limited
The inverter's output power has reached its rated limit and is being capped. Restart the system and check whether the fault clears. If the fault cannot be cleared, the inverter output stage may need inspection — contact AlphaESS support.
Safety & protection

Ground fault detection, arc fault protection, insulation monitoring, overtemperature shutdown, and fan failure alarms. These codes indicate safety-critical conditions — some require the system to be isolated before any inspection.

100008 — GFCI_fault ⚠ Ground fault — isolate system
Ground fault current detected. If accompanied by an insulation resistance alarm (100007), follow the insulation fault troubleshooting steps first. If it occurs frequently with other alarms and the inverter cannot connect to the grid, the GFCI circuit inside the inverter may be faulty — do not restart without professional assessment.
100058 — AFCI_check_protect Inverter error — arc fault protection
The arc fault detection circuit has triggered. Restart the system and check whether the fault persists. If it does, a DC arc may be present in the PV string or battery cabling — do not touch DC connectors. Contact a qualified engineer to inspect all DC connections for signs of arcing, melting, or discolouration.
110006 — over_temperature_alarm Alarm — inverter overheating
The inverter's internal temperature has exceeded its safe operating limit. Check whether the installation is in direct sunlight, whether ventilation is adequate, and whether the ambient temperature exceeds 45°C. If the environment is within limits and the alarm persists, the internal cooling fan or temperature sensor may be faulty — contact AlphaESS support.
110029 — GFCI Alarm Alarm — ground fault warning
Ground fault current interrupter has triggered at the alarm (warning) level. If accompanied by insulation fault alarms, follow the insulation fault guidance. If it occurs frequently and the inverter cannot connect to the grid, the inverter's GFCI circuit may need replacement — contact AlphaESS support.
110030 — ISO Alarm Alarm — insulation monitoring
Insulation monitoring alarm — the system has detected a potential insulation degradation event. Restart the system and check whether the fault persists. If it does, the PV string insulation may need testing by a qualified engineer with a megohmmeter.
110034 — Fan Abnormal Alarm Alarm — cooling fan fault
The inverter's cooling fan is not operating correctly. Check via the Alpha Cloud app whether the internal temperature has reached 60°C — if an external fan triggered the alarm, power off, restart, and observe whether the external fan is running. Inspect the fan for blocked vents, damage, or foreign objects. If an internal fan is faulty, the inverter will require a service visit to replace it.
System & firmware

Internal system errors related to firmware, memory, DSP communication, and the 12V auxiliary supply. These typically require AlphaESS support involvement for remote firmware updates or hardware diagnosis.

100060 — Dsp_selfcheck Inverter error — DSP self-check failed
The inverter's internal DSP processors are not compatible. This is a hardware-level fault — the inverter requires professional repair. Contact AlphaESS support to arrange a service or replacement unit.
100122 — EEPROM R/W Failure Inverter error — memory read/write
The inverter's EEPROM memory has failed a read/write operation. If a remote firmware upgrade was recently performed and the inverter is operating normally, this is a normal transient result of the upgrade process. If it persists or the inverter is not operating, contact AlphaESS support.
100123 — DSP communication failure Inverter error — DCDC module comms
Communication between the inverter and its internal DCDC module has been lost. Contact AlphaESS support to attempt a remote DCDC module firmware upgrade. If that does not restore communication, fully power off the inverter for 10 minutes and restart. Persistent faults require professional inspection.
100145 — 12V auxiliary power Fault Inverter error — 12V supply failed
The inverter's internal 12V auxiliary power supply has failed. An occasional occurrence may recover automatically. If it continues to appear, the 12V supply board inside the inverter is faulty and will require a hardware repair or replacement — contact AlphaESS support.
100165 — data storage error Inverter error — data storage
An error has occurred in the inverter's internal data storage. An occasional occurrence recovers automatically. If persistent, the inverter's storage hardware is faulty — contact AlphaESS support for diagnosis and potential replacement.
110036 — FLASH ID Alarm Alarm — flash memory ID
Flash memory identification error. Restart the system and check whether the fault persists. If it does, contact AlphaESS support — the flash memory chip may require replacement or the firmware may need to be reflashed.
110037 — ReadFlash Alarm Alarm — flash memory read
The inverter cannot read from its flash memory correctly. Restart the system. If persistent, contact AlphaESS support for a firmware reflash or hardware inspection.
110039 — Machine Type Alarm Alarm — firmware model mismatch
The firmware loaded on the inverter does not match the physical hardware model. This typically occurs after an incorrect firmware update has been applied. Contact AlphaESS support to load the correct firmware version for your inverter model.
Code not listed here?

AlphaESS may release new error codes with firmware updates, and different SMILE hardware generations can have additional codes not shown here. Share the exact numeric code from your LCD or Alpha Cloud alarm history and we'll identify it. AlphaESS also maintain support via cloud.alphaess.com.

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AlphaESS fault code questions

Fault codes appear on the inverter LCD display and in Alpha Cloud. On the SMILE5, press ENT to enter the menu, then navigate to Status to view active alarms. In Alpha Cloud (cloud.alphaess.com), open My System and check the alarm history for timestamped error codes. Each code has a numeric identifier like 100007 or 110021 that you can look up in this index.

Many 110xxx alarm codes clear automatically once the triggering condition resolves — for example, a Grid Volt Alarm clears when mains voltage returns to normal. For persistent 100xxx error codes, a full power cycle (switch off the AC breaker, battery breaker, and PV isolator, wait five minutes for capacitors to discharge, then restore power in reverse order) can clear transient faults. If the same code returns after a power cycle, the underlying issue requires diagnosis rather than repeated restarting.

A red fault LED on the SMILE inverter indicates an active hardware or protection fault. The LCD screen shows the specific numeric error code. Common causes include grid relay faults, insulation resistance failures, battery communication loss, and DC bus voltage problems. Note the code from the display and look it up in this index before taking any action — some codes indicate conditions where the system should not be touched without a qualified engineer present.

STS offers remote diagnostic assessments from £75. Our engineers can access your Alpha Cloud monitoring data remotely to analyse fault history, system performance, and configuration without visiting site. The diagnostic identifies the root cause and recommends whether a settings change, firmware update, or on-site repair is needed — saving you the cost of an unnecessary callout.

Error 100007 (Insulation_fault) is one of the most common AlphaESS alarm codes and is typically caused by moisture on PV panel cables or junction boxes — it often appears during or after rain and clears when conditions dry out. If it occurs frequently in dry weather, the insulation resistance of one or more PV strings has degraded. An engineer can isolate individual strings and test with a megohmmeter to identify the affected circuit. Persistent insulation faults should not be ignored as they indicate a potential safety issue.

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