Fault code index · SolaX X-Hybrid all models
SolaX Fault Code Index
Every SolaX X-Hybrid inverter and T-BAT / Triple Power battery fault code — what it means, the most likely cause, and what to do. Find your code in the index below or use the category sections to browse by system area.
X1-Hybrid, X3-Hybrid, X1-Boost & X3-Mega
T-BAT & Triple Power battery codes included
Sourced from SolaX technical documentation
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How to find your fault code. SolaX fault codes appear on the inverter LCD display and in the SolaX Cloud app under the fault or alarm history. Grid and inverter faults use short names (Grid Volt, PLL Lost, Isolation). Battery charger faults are prefixed with C1 (e.g. C1 CAN, C1 TEMP). BMS faults use the BMS_ prefix. Match your code to the categories below.
Grid & AC faults
Fault codes triggered when grid voltage or frequency is outside safe limits, or the grid connection is lost. The inverter disconnects as required by UK grid codes G98/G99 and reconnects automatically when conditions normalise.
Grid Volt / E012
⚠ Most common
Grid voltage outside the 216V–253V safe range. Almost always overvoltage above 253V during peak solar export. The inverter reconnects automatically when voltage drops. If recurring every sunny afternoon, this is a network issue — report to your DNO and consider export limitation.
Grid Freq
Grid frequency error
Grid frequency outside the safe range (47.5Hz–52Hz). Caused by grid instability, not an inverter fault. The inverter reconnects automatically when frequency normalises. Single events after storms or outages are normal. Recurring events suggest a weak grid connection.
Grid Lost / IE02
No grid connection detected
Inverter cannot measure grid voltage at all. Check: AC isolator is on, consumer unit breaker for the solar circuit has not tripped, AC cable connections at the inverter are tight. If mains power is present and all connections are secure, the internal grid relay may be faulty.
PLL Lost
Grid sync failure
The inverter lost synchronisation with the grid frequency — it could not maintain a stable phase lock. Often occurs during grid instability after storms or power cuts. Usually clears within minutes. If persistent, check AC wiring and neutral connections.
AC5M Volt
Voltage out of range 5 min
Grid voltage has been outside the acceptable range for more than five consecutive minutes. The inverter has shut down to protect itself. More serious than a brief Grid Volt trip — suggests a sustained grid voltage problem. Check SolaX Cloud for the voltage reading and contact your DNO.
AC10M Volt
Voltage out of range 10 min
Grid voltage has been outside specification for more than ten minutes. The grid at your property is persistently unstable. This requires DNO investigation — the distribution network may need reinforcement or the transformer tap may need adjusting.
Grid Relay
Internal relay fault
Internal grid relay switch malfunction. Can be caused by a poorly connected neutral line or three-phase unbalance on X3-Hybrid systems. Try a full power cycle first. If the fault returns, the relay or inverter may need replacement — contact an engineer.
DC & Insulation faults
Fault codes related to the DC solar input — panel voltage, insulation resistance, and PV array configuration. Isolation faults are safety-critical and should not be restarted without inspection.
PV Volt
PV voltage error
DC input voltage from the solar panels is outside the acceptable range — either too high (too many panels in series) or too low (insufficient sunlight, DC isolator off, or a broken string). Check the DC isolator is on and MC4 connections are secure. If voltage is above the inverter's maximum input rating, the string design needs reviewing by an installer.
Isolation
⚠ URGENT — do not restart
Insulation resistance between the DC circuit and earth has dropped below the safe threshold. This is a safety-critical fault — electricity is leaking from the DC wiring. Do not restart the system. Common causes: water ingress at MC4 connectors, damaged cable insulation, or a faulty panel junction box. Contact a qualified engineer for inspection before any restart.
PV Config.
PV array configuration error
The PV array configuration in the inverter settings does not match the physical panel connections. This can occur after a panel replacement or if the string configuration was changed without updating the inverter settings. Check MPPT input assignments and PV configuration in the inverter menu.
Internal inverter faults
Fault codes originating from inside the inverter — processor communication, cooling, overcurrent protection, and memory errors. Try a full power cycle first. If the fault returns, the inverter needs professional diagnosis.
SPI
SPI communication fault
Internal processor communication error. The inverter's internal components have lost synchronisation. Perform a full power cycle — AC off, DC off, wait 60 seconds, DC on, AC on. If the fault returns, the control board may need firmware reflash or replacement.
SCI
SCI communication fault
Internal SCI serial communication has failed. Similar to SPI — an internal processor issue. Power cycle the system. If persistent, the main control board or DSP may need replacement. This is not user-serviceable.
Bus Volt
DC bus voltage out of range
The internal DC bus voltage is too high or too low. This is the voltage on the inverter's internal power conversion stage — not the panel input. Often caused by a grid voltage spike or a transient event. Power cycle first. If persistent, the inverter's power stage may be failing.
Inv OCP
Overcurrent protection
Inverter has detected current above the safe limit on the AC output. May self-clear after a brief overload event. If persistent, check for a short on the AC output wiring or an internal inverter fault. Do not keep restarting if the fault returns immediately.
Temp Over
Overtemperature shutdown
Internal temperature has exceeded the thermal shutdown threshold. Check ventilation clearances (minimum 20cm all sides), ensure no direct sunlight on the inverter, and clear any dust from cooling vents. If the environment is cool and ventilation is adequate, the internal temperature sensor may be faulty.
Fan1 / Fan2
Cooling fan failure
One or both internal cooling fans are not spinning or running at an abnormal speed. The inverter will derate or shut down to prevent overheating. Check for debris blocking the fan intake. If the fan has seized, it needs replacement — this is a common wear item on older X-Hybrid units.
Relay
Relay malfunction
Internal relay switch has failed its self-test. The inverter cannot safely connect to the grid. Power cycle first. If the fault returns, the relay has worn out or failed — the inverter needs professional repair or replacement. This is more common on older units with high switching cycles.
RCD
Residual current device fault
The inverter's internal RCD has detected a leakage current. This is a safety protection — do not ignore it. It may indicate an earth fault on the AC side. Check AC wiring connections. If persistent, the inverter or the AC wiring needs professional inspection.
Inv. EEPROM
Internal memory fault
The inverter's EEPROM memory chip has experienced an error. Settings or calibration data may be corrupted. A firmware reflash may resolve the issue. If the fault persists after a power cycle, the control board likely needs replacement.
Sample
Detection circuit failure
The inverter's internal voltage or current detection circuit has failed its self-check. The inverter cannot accurately measure its own output and has shut down as a safety measure. Requires professional diagnosis — the measurement circuits may need recalibration or the control board may be faulty.
TZ Protect
Overcurrent protection triggered
The inverter's internal overcurrent protection mechanism has been activated. Similar to Inv OCP but triggered by the hardware protection circuit rather than the software limit. Power cycle first. If persistent, the output stage or power components may be damaged.
DCI Device
DC injection device fault
The DC injection monitoring circuit has detected a fault. This safety circuit ensures no DC current enters the AC grid. A power cycle may clear a transient fault. If persistent, the DCI monitoring hardware needs professional inspection.
RTC
Real-time clock fault
The inverter's internal clock has malfunctioned. This can cause ForceTime and TOU schedules to run at the wrong time, and SolaX Cloud timestamps to be incorrect. A power cycle and clock resync via SolaX Cloud usually resolves this. If persistent, the RTC battery on the control board may need replacing.
Battery charger faults (C1)
C1-prefixed codes relate to the battery charger circuit inside the X-Hybrid inverter. These affect battery charging and discharging but solar generation to the grid may continue.
C1 CAN
⚠ Common — battery comms lost
Communication between the inverter and battery via CAN bus has failed. The most common cause is a loose CAN cable, wrong battery type selected in inverter settings (T-BAT vs Triple Power), or a missing termination resistor. See our BMS communication fault guide.
C1 TEMP
Charger overtemperature
The battery charger circuit inside the inverter is running too hot. Check ventilation clearances and ambient temperature. If the inverter is in a confined space or exposed to direct sunlight, relocating or improving airflow may resolve the issue. The charger will resume when temperature drops.
C1 FAN
Charger fan failure
The cooling fan for the battery charger section is not working. Dust or debris may be blocking the fan. If the fan has seized, it needs replacement. Without cooling, the charger will overheat and stop charging the battery.
C1 Bat OVP
Battery overvoltage
Battery voltage has exceeded the safe maximum. The charger has stopped to protect the battery cells. This can indicate a BMS fault, a cell imbalance, or incorrect battery settings. Do not keep restarting — the battery needs professional inspection to check cell voltages and BMS health.
C1 Bus OVP
Charger bus overvoltage
The internal DC bus voltage in the charger circuit has exceeded the safe range. Often a transient event that clears with a power cycle. If persistent, the charger's power conversion stage may be failing and needs professional diagnosis.
C1 TZ
Charger protection triggered
Hardware overcurrent protection in the charger circuit has been activated. The charger has shut down to prevent damage. Power cycle first. If persistent, the charger's power components may be damaged — professional repair is needed.
C1 EEPROM
Charger memory fault
The charger section's EEPROM memory has experienced an error. Calibration or configuration data may be corrupted. A firmware update may resolve the issue. If the fault persists after a power cycle, the charger control board needs attention.
C1 Temp Low
Charger below min temperature
The charger is too cold to operate safely — the ambient temperature has dropped below the minimum operating threshold. Common in unheated garages or outbuildings during winter. The charger will resume when the temperature rises. Insulating or heating the space may help in cold climates.
C1 HCT1 / HCT2
Charger current sensor fault
The current measurement sensor in the charger circuit has failed its self-check. The charger cannot accurately measure how much current is flowing to or from the battery. Professional repair needed — the sensor or control board may need replacement.
C1 Charger OCP / Boost OCP
Charger overcurrent
Overcurrent detected in the charger or boost circuit. Too much current is flowing through the charging path. This can be caused by a battery fault, a short in the DC battery wiring, or a failing power component in the inverter. Power cycle first — if it returns, professional diagnosis is needed.
Battery BMS faults
BMS (Battery Management System) faults relate to the T-BAT or Triple Power battery itself — communication, isolation, relay, and internal errors. See our dedicated BMS fault guide for full diagnosis steps.
BMS_Lost
⚠ Common — battery not detected
The inverter cannot detect the battery at all — the CAN bus communication link is completely down. Check the CAN cable at both ends, verify the battery type setting matches the installed hardware (T-BAT vs Triple Power), and check the 120Ω termination resistor is in place. See our BMS fault guide.
BMS_Internal_Err
BMS internal error
Usually caused by a DIP switch misconfiguration on stacked battery modules, or a loose CAN cable at the battery management unit. Check DIP switch positions match the number of modules installed (0 for one, 1 for two, 2 for three). Also check all inter-module RS485 cables on stacked systems.
BMS Relay Fault
BMS relay failure
The battery's internal relay has failed. Try resetting the BMU (Battery Management Unit) by power cycling the battery. If the fault persists after restart, the BMU may need replacement. This is not user-serviceable — contact an engineer.
BMS_ISO Fault
Battery isolation fault
Insulation resistance within the battery system has dropped below the safe threshold. This is a safety-critical fault — do not restart without professional inspection. Possible causes include water ingress into the battery enclosure, damaged internal wiring, or a failing battery cell.
BMS Circuit Fault
BMS internal circuit failure
An internal circuit within the BMS has failed. Try a full battery power cycle — turn off the battery, wait 60 seconds, turn it back on. If the fault returns, the BMS control board needs replacement. This fault typically requires on-site repair.
Monitoring & metering faults
Faults related to the CT clamp, smart meter, EPS (backup) mode, and monitoring connectivity. These typically do not stop solar generation but may affect battery control, export limiting, or monitoring accuracy.
CT
CT clamp / smart meter error
The current transformer (CT clamp) or smart meter connected to the inverter is not reading correctly. This affects export limitation accuracy and self-use calculations. Check the CT clamp is clamped around the correct cable, oriented in the right direction, and securely connected to the inverter's meter port. If using a smart meter instead of CT, check the RS485 connection.
AC HCT
AC current sensor fault
The inverter's internal AC current sensor has failed. The inverter cannot accurately measure its own AC output. This is an internal hardware fault — the system will shut down as a safety measure. Professional repair or inverter replacement is needed.
Overload (EPS)
EPS mode overload
Too much power is being drawn in Emergency Power Supply (backup) mode. The connected loads exceed the inverter's EPS output rating. Reduce the load on the backup circuit — disconnect high-power appliances. If EPS overload occurs during a power cut, the backup circuit may need redesigning to include only essential loads.
EPS Relay
EPS relay failure
The relay that switches the inverter into backup mode has failed. The system will not provide backup power during a grid outage. Solar generation and grid-connected operation may still work normally. The EPS relay needs professional replacement.
EPS OCP
EPS overcurrent
Overcurrent detected in the EPS output — more current is being drawn than the inverter can safely supply in backup mode. This is similar to Overload but triggered by the hardware protection. Reduce the load on the backup circuit immediately.
DM9000
Network DSP fault
The network digital signal processor — responsible for the Pocket WiFi dongle communication — has malfunctioned. SolaX Cloud monitoring may go offline but the inverter and battery continue operating normally. A power cycle usually clears this. If persistent, the communication module may need replacing.
Frequently asked questions
How do I find fault codes on my SolaX inverter? ↓
Fault codes appear on the inverter LCD display and in the SolaX Cloud app under fault or alarm history. Grid and inverter faults use short names (Grid Volt, PLL Lost, Isolation). Battery charger faults are prefixed with C1 (e.g. C1 CAN, C1 TEMP). BMS faults use the BMS_ prefix. Match your code to the categories in this index.
What do SolaX fault codes starting with C1 mean? ↓
C1 codes relate to the battery charger circuit inside the X-Hybrid inverter. C1 CAN means communication with the battery has failed. C1 TEMP means the charger is overheating. C1 Bat OVP means battery voltage is too high. Most C1 codes need a power cycle first — if the fault returns, professional diagnosis is needed.
Can I restart my SolaX to clear a fault code? ↓
Grid faults (Grid Volt, Grid Freq) clear automatically when grid conditions normalise. For internal faults, a power cycle can clear transient errors — AC off, DC off, wait 60 seconds, DC on, AC on. If the same fault returns after restart, the issue is persistent and needs diagnosis. Isolation faults and BMS_ISO faults should not be restarted without professional inspection.
Why does my SolaX show Grid Volt every sunny afternoon? ↓
A recurring Grid Volt fault during sunny afternoons means mains voltage at your property is exceeding 253V when multiple local solar systems are exporting simultaneously. The inverter disconnects because UK grid code requires it — this is correct behaviour, not a defect. Report the issue to your DNO with voltage readings from SolaX Cloud. Consider configuring export limitation on your inverter to reduce your contribution to the voltage rise.
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