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Fault code index · LuxPowerTek LXP hybrid & SNA off-grid

LuxPowerTek Fault Code Index

Every LuxPowerTek inverter error and warning code from the official LXP hybrid and SNA off-grid manuals — what each E-code and W-code means, the most likely cause, and what to do next. Covers LXP 3–6K, LXP 4–6K HB, and SNA 3–5K models.

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Sourced from official LuxPowerTek manuals Covers hybrid and off-grid inverter series E-codes (errors) and W-codes (warnings)

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Grid & AC PV / Solar Battery / BMS UPS / EPS Parallel system Internal
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How to find your fault code. LuxPowerTek inverters display fault codes on the LCD screen with a code number and short description. Navigate to Error Record on the LCD for timestamped error history, or Alarm Record for warnings. The red LED lights for faults (E-codes) and yellow LED for warnings (W-codes). Codes are also visible in the Luxpower View monitoring portal at server.luxpowertek.com.
Grid & AC faults

Faults and warnings triggered by problems with the AC mains supply, grid voltage, grid frequency, or meter connections. Warning codes self-clear when conditions normalise; error codes stop the inverter.

E023 — Neutral fault LCD: E023 · LXP hybrid series
Check the neutral connection at the inverter AC terminal. A loose or missing neutral prevents proper AC operation. Verify the neutral-earth bond at the consumer unit if this fault persists after checking connections.
W016 — No AC connection LCD: No AC connection · LXP hybrid
The inverter cannot detect AC mains input. Check the AC breaker is switched on, verify the MCB on the solar circuit in the consumer unit hasn't tripped, and check the AC terminal connections at the inverter are tight. If grid power is present elsewhere in the property, the issue is between the consumer unit and the inverter.
W017 — AC voltage out of range LCD: AC V Outrange · LXP hybrid
Mains voltage is outside the acceptable 180–270V range. Usually caused by the DNO supply — voltage is commonly high in rural areas. Monitor with a plug-in voltage meter. If consistently above 253V, contact your DNO to request a tap change. The inverter restarts automatically once voltage returns to range.
W018 — AC frequency out of range LCD: AC F Outrange · LXP hybrid
Grid frequency is outside the 45–65Hz tolerance. Rare in the UK — usually caused by a temporary grid disturbance or a generator running at incorrect speed. Self-clears once grid conditions normalise.
W030 — Meter connection reversed LCD: Meter Reversed · LXP hybrid
The CT clamp or meter connection is installed backwards, causing incorrect import/export readings. This affects battery charging logic — the inverter may charge from grid instead of solar. Reverse the CT clamp orientation or swap the meter cable polarity.
PV / Solar faults

Fault codes caused by problems with the solar panel DC input — overvoltage, short circuits, and insulation failures. PV voltage errors are serious and may indicate an unsafe string configuration.

E021 — PV voltage high ⚠ Do not touch DC cabling
PV input voltage exceeds 500V (LXP) or 480V (SNA). Do not touch any DC cabling. This may indicate too many panels wired in series on one string. Wait for the inverter to restart — if the fault persists, the string configuration needs to be reviewed by a qualified engineer.
E024 — Both PV short circuit ⚠ Disconnect PV at DC isolator
Short circuit detected on both PV string inputs simultaneously. Disconnect both PV strings at the DC isolator. Check MC4 connector integrity and cable condition. If the fault clears with PV disconnected, reconnect one string at a time to identify which is faulty.
W020 — PV isolation low LCD: PV Isolation low · LXP hybrid
Insulation resistance between the DC circuit and earth is below the safe threshold. Commonly caused by moisture ingress into panel junction boxes or damaged cable insulation. Often appears during or after rain and clears when conditions dry. Persistent faults in dry weather require professional insulation testing with a megohmmeter.
W023 — PV short circuit LCD: PV short · LXP hybrid
Short circuit detected on one PV string input. Check the MC4 connectors on the affected string for damage or moisture. Disconnect the string at the DC isolator and inspect the cable run for physical damage.
Battery & BMS

Codes related to battery communication, voltage limits, temperature sensors, and hardware failures. W000 (battery communication fault) is the most common Lux warning in UK installations.

E002 — Bat On Mos Fail ⚠ Hardware fault — SNA series
The battery MOSFET switching circuit has failed. This is a hardware fault in the inverter's battery charging circuit. Power cycle the inverter — if the fault returns, the inverter requires professional repair.
W000 — Battery communication fault LCD: Bat Com Fault · all series
The inverter cannot communicate with the battery BMS over CAN or RS485. Check the communication cable is seated correctly in the battery CAN/RS485 port and the inverter's Li-ion CAN/RS485 port. Verify the battery brand is correctly selected in the inverter settings. If using third-party batteries, confirm the BMS protocol is compatible. BMS comm fault guide →
W003 — Meter communication fault LCD: Meter Com Fault · LXP hybrid
The inverter cannot communicate with the energy meter over the RS485 bus. Check the meter communication cable connections at both ends. If the cable is intact, the meter itself may be faulty or the RS485 address setting may be incorrect.
W004 — Battery failure LCD: Battery failure · all series
The battery BMS has reported a fault condition to the inverter. Restart the battery by switching it off at its isolator, waiting 60 seconds, then switching back on. If the warning persists, the issue is internal to the battery — contact the battery manufacturer or an engineer.
W025 — Battery voltage high LCD: Bat Volt High · all series
Battery voltage has exceeded the safe upper threshold. Check that the correct battery type and voltage settings are configured in the inverter. Lithium batteries reporting high voltage may have a faulty cell or BMS issue requiring professional investigation.
W026 — Battery voltage low LCD: Bat Volt Low · all series
Battery voltage has dropped below the low warning threshold. The battery needs charging. If the battery is supposed to be charging but voltage remains low, check the charge settings and verify AC input is present. Persistently low voltage on a lithium battery may indicate a failed cell.
W027 — Battery open circuit LCD: Bat open · all series
The inverter detects that the battery is disconnected or stuck in an open state. Check the battery isolator is switched on and the DC cable connections between battery and inverter are secure. Restart the entire system — battery first, then inverter. If the warning persists, there may be a blown fuse inside the battery.
UPS / EPS faults

Faults on the backup power (UPS/EPS) output — short circuits, overloads, and wiring errors. These codes appear when the backed-up circuit has an issue.

E012 — UPS short circuit ⚠ Disconnect loads immediately
Short circuit detected on the UPS/EPS output. Turn off all loads connected to the backup circuit. Disconnect the UPS connector and restart the inverter. If the fault clears with UPS disconnected, the issue is a short in the backed-up circuit wiring or one of the connected appliances. Reconnect loads one at a time to identify the culprit.
E013 — UPS power reversed ⚠ Wiring fault — qualified electrician
The AC wiring between the UPS output and the backed-up circuit is connected with reversed polarity. Switch off the inverter and check the L/N wiring at the UPS output terminal. This must be corrected by a qualified electrician.
E020 — UPS connection fault LCD: E020 · all series
Check the UPS/EPS wiring and AC connections. Verify the EPS output is correctly wired to the backed-up circuit in the consumer unit. If the UPS/EPS output has never worked since installation, the wiring configuration may be incorrect.
W028 — UPS over load LCD: UPS Over Load · all series
The total load on the backed-up circuit exceeds the inverter's UPS rated output (typically 5kW). Reduce the load by disconnecting high-power appliances from the backed-up circuit. Persistent overload will cause the inverter to shut down UPS output to protect itself.
Parallel system faults

Error codes specific to multi-inverter parallel installations. These only appear when two or more Lux inverters are connected via CAN bus in a parallel configuration. Single-inverter systems will never show these codes.

E001 — Model fault LCD: E001 · parallel config error
The parallel CAN cables between inverters are incorrect or the balance resistor switch is in the wrong position. Check that CAN cables are connected to the correct ports and the safety standard switch matches the installation configuration.
E008 — Parallel CAN fault LCD: E008 · CAN bus failure
Communication failure between paralleled inverters over the CAN bus. Check CAN cable connections between all inverters in the parallel system. Verify the CAN termination resistor DIP switch is set correctly — only the first and last inverter in the chain should have termination enabled.
E009 — Primary loss LCD: E009 · master inverter missing
The parallel system has lost its designated primary (master) inverter. Check CAN cables between primary and subordinate units. Verify one inverter is configured as primary and the others as subordinates. If the primary inverter has shut down due to another fault, resolve that fault first.
E010 — Multiple Primary LCD: E010 · duplicate master config
Two or more inverters are configured as primary in the parallel system. Only one inverter should be set as primary — reconfigure all others as subordinates through the LCD settings menu or Luxpower View portal.
E011 — Parallel AC inconsistent LCD: E011 · AC mismatch
The AC supply voltage or phase angle is different between paralleled inverters. Check that all inverters are connected to the same AC supply phase and that the wiring between them is consistent.
E015 — Parallel phase abnormal LCD: E015 · three-phase assignment
In a three-phase parallel system, the phase assignment is incorrect. Check the AC connections and verify each inverter is assigned to the correct phase (R, S, or T) in the parallel settings.
Internal & hardware faults

Internal processor communication failures, relay faults, overcurrent, overtemperature, and bus voltage errors. Most require a restart as a first step — persistent codes typically indicate hardware failure.

E000 — Internal communication fault 1 LCD: E000 · DSP comm failure
Communication failure between the main and subordinate DSP processors inside the inverter. Restart the inverter — if the fault persists, a firmware update may resolve it. If neither works, the inverter requires professional repair.
E016 — Relay fault ⚠ Safety isolation — do not bypass
The internal AC relay has failed to open or close correctly. This is a hardware failure — restart the inverter, and if the fault persists, the relay needs professional replacement. Do not bypass the relay as it serves a critical safety isolation function.
E019 — Bus voltage high LCD: E019 · DC bus overvoltage
The internal DC bus voltage has exceeded the safe threshold. This can be triggered by PV input voltage being too high or by a fault in the bus capacitor circuit. Wait for the inverter to auto-restart — if it repeats, disconnect PV and have the system inspected.
E022 — Over current LCD: E022 · internal overcurrent
Internal overcurrent protection has triggered. This may be caused by a sudden large load spike, an internal component failure, or a short circuit. Restart the inverter — if persistent, the inverter needs professional diagnosis.
E025 — Temperature over range LCD: E025 · overtemperature shutdown
The inverter's internal temperature has exceeded the safe operating limit (typically 60°C). Check the heat sink is clear of obstructions and dust. Ensure the inverter has adequate ventilation clearance (minimum 300mm on all sides). If installed in direct sunlight, consider adding shading. The inverter restarts automatically once it cools down.
E026 — Internal fault LCD: E026 · general hardware fault
A general internal hardware fault — covers bus sampling errors and other internal failures. Restart the inverter. If persistent, a firmware update may resolve software-related internal faults. Hardware faults require professional repair.
E027 — Sampling inconsistent LCD: E027 · LXP hybrid only
Measurement samples between the main and subordinate CPU do not agree. This is a safety check — the inverter shuts down when processors disagree. Restart — if persistent, it indicates a hardware fault with one of the measurement circuits and requires professional diagnosis.
E031 — Internal communication fault 4 LCD: E031 · DSP comm failure variant
Communication failure between DSP processors (fourth variant). Same approach as E000 — restart, try firmware update, then professional repair if persistent.
W005 — Auto Test failure LCD: Auto Test failure · LXP hybrid
The inverter's automatic self-test has failed during startup. Restart — if persistent, a firmware update may resolve it. Persistent Auto Test failures prevent grid connection and require professional diagnosis.
W009 — Fan Stuck LCD: Fan Stuck · SNA off-grid
The internal cooling fan is not spinning. Check for obstructions blocking the fan. Dust buildup can jam the fan — clean with compressed air. If the fan has failed mechanically, it needs replacement to prevent overheating.
W021 — Leakage current high LCD: Leakage I high · LXP hybrid
High leakage current detected between DC and earth. Check PV string insulation and earth bonding connections. Similar to W020 but indicates current flow rather than low resistance. Restart the inverter — if persistent, requires professional earth leakage testing.
W022 — DC injection high LCD: DC Injection high · LXP hybrid
The inverter is injecting excessive DC current into the AC grid — exceeding the allowed threshold. This is a grid compliance safety check. Restart the inverter. If persistent, the inverter's output filter capacitors or measurement circuits may be faulty and require professional inspection.
Code not listed here?

LuxPowerTek add new fault codes with firmware updates, and some codes are specific to newer GEN series models not covered in the original LXP and SNA manuals. If your code isn't listed, share the exact text from the inverter LCD or Luxpower View alarm log and we'll identify it.

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Full diagnostic guides by fault type
W000 · Bat Com Fault · CAN/RS485
BMS communication fault

Full diagnostic — CAN/RS485 cable, battery brand setting, DIP switches, and firmware compatibility.
Charge schedule · time-of-use · Agile
Octopus cheap rate charging

Timer settings, Agile mode, force charge, and Luxpower View configuration.
Manuals · datasheets · wiring diagrams
LuxPowerTek documents

Official LXP and SNA user manuals, wiring diagrams, and quick-start guides.

LuxPowerTek fault code questions

LuxPowerTek inverters display fault codes on the LCD screen with a code number and short description. Navigate to Error Record on the LCD for timestamped error history, or Alarm Record for warnings. The red LED lights for faults (E-codes) and yellow LED for warnings (W-codes). Codes are also visible in the Luxpower View monitoring portal at server.luxpowertek.com under alarm history.

Many E-codes clear after a full power cycle. Cut off the AC breaker, switch off the DC battery isolator, wait 10 minutes for capacitors to discharge, then restore in reverse order — battery first, then AC. Warning codes (W prefix) often self-clear when the condition resolves. If the same E-code returns after restart, the fault is persistent and needs professional diagnosis.

E-codes are errors — the inverter stops working and the red LED lights up. W-codes are warnings — the inverter continues to operate but with a yellow LED alert. E-codes require immediate attention while W-codes can sometimes be monitored. Both are logged with timestamps in the Error Record and Alarm Record menus on the LCD.

STS offers remote diagnostic assessments from £75. We can access your Luxpower View monitoring data remotely to analyse fault history and system performance 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.

W000 (Bat Com Fault on the LCD) means the inverter cannot communicate with the battery BMS. The most common causes are an incorrect battery brand selection in the inverter settings, a loose or damaged CAN/RS485 cable between battery and inverter, or the communication cable plugged into the wrong port. Check the battery type setting in the inverter menu first — it must match the exact battery brand and model connected. See our full BMS comm fault guide for step-by-step diagnosis.

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