FoxESS Inverter Error Codes
FoxESS hybrid (H1/AC1) named alarms and R-series numeric fault codes in plain English — what each means and what to check.
- Manufacturer
- FoxESS (H1/AC1 hybrid inverters and R-series three-phase string inverters)
- Codes documented
- 48
- Source
- Manufacturer documentation
- Scope
- Reference only
FoxESS uses two distinct fault-naming conventions across its range. The hybrid inverters (H1/AC1, including the G2 generation) report named text alarms such as `Grid Lost Fault`, `Bat Volt Fault` and `BMS Lost`, shown on the inverter panel or in FoxCloud. The R-series three-phase string inverters (R75/R100/R110) use numeric fault codes in the 1030–1345 range. Every code below is taken verbatim from FoxESS's own user manuals (the H1(G2)/AC1(G2) Manual V1.0.8 and the R-Series User Manual), with the legacy numeric grid codes (1, 26, 27, 28) corroborated against the FoxESS owners' community forum. Always confirm the exact wording on your own unit's display or in FoxCloud, as alarm sets vary by model and firmware.
- 48 FoxESS (H1/AC1 hybrid inverters and R-series three-phase string inverters) fault and alarm codes, documented in plain English.
- Compiled from manufacturer documentation — independent and not affiliated with FoxESS (H1/AC1 hybrid inverters and R-series three-phase string inverters).
- Codes involving DC/AC isolators, wiring or opening the unit are licensed-electrician work — when in doubt, call your installer.
48 of 48 codes
- Grid Lost Fault
Grid Lost Fault
The grid supply has been lost / disconnected, so the inverter has isolated from the grid. Often appears alongside grid voltage/frequency faults, frequently caused by a tripped breaker.
What to do
System will reconnect automatically once the utility returns to normal. If it does not return to normal, seek help from FoxESS.
- Grid Volt Fault
Grid Voltage Fault
Measured grid voltage is outside the allowed operating range (over- or under-voltage).
What to do
System will reconnect once the utility returns to normal; otherwise seek help from FoxESS.
- Grid Freq Fault
Grid Frequency Fault
Grid frequency is outside the allowed operating range.
What to do
System will reconnect once the utility returns to normal; otherwise seek help from FoxESS.
- 10min Volt Fault
10-Minute Average Grid Voltage Fault
The 10-minute average grid voltage has been out of range, a regulatory over-voltage protection.
What to do
System will reconnect once the utility returns to normal; otherwise seek help from FoxESS.
- Bat Volt Fault
Battery Voltage Fault
Battery voltage is outside the inverter's normal operating range.
What to do
Check that the battery input voltage is within the normal range; otherwise seek help from FoxESS.
- Pv Volt Fault
PV Voltage Fault
PV (solar) input voltage is outside the allowed range.
What to do
Check the output voltage of the PV panels; otherwise seek help from FoxESS.
- Iso Fault
Isolation (Insulation) Fault
Isolation/insulation resistance to ground has failed, typically from damaged cable insulation or moisture.
What to do
Check whether the insulation of the electric wires is damaged; wait to see if it returns to normal; otherwise seek help from FoxESS.
- Res Cur Fault
Residual Current Fault
Detected residual (leakage) current is too high, often from damaged insulation.
What to do
Check whether the insulation of the electric wires is damaged; wait to see if it returns to normal; otherwise seek help from FoxESS.
- DCI Fault
DCI (DC Injection) Fault
The DC component in the AC output current exceeds the permitted limit.
What to do
Disconnect PV, grid and battery, then reconnect; otherwise seek help from FoxESS.
- SW Inv Cur Fault
Software Inverter Current Fault
Output current detected as too high by the software protection.
What to do
Disconnect PV, grid and battery, then reconnect; otherwise seek help from FoxESS.
- HW Inv Cur Fault
Hardware Inverter Current Fault
Output current detected as too high by the hardware protection.
What to do
Disconnect PV, grid and battery, then reconnect; otherwise seek help from FoxESS.
- Temp Fault
Over-Temperature Fault
The inverter internal/ambient temperature is too high.
What to do
Check the environment temperature; wait to see if it returns to normal; otherwise seek help from FoxESS.
- Ground Fault
Ground Connection Fault
The ground (PE) connection has failed.
What to do
Check the voltage of neutral and PE, check AC wiring, then disconnect PV/grid/battery and reconnect; otherwise seek help from FoxESS.
- Over Load Fault
Overload Fault (On-Grid)
The connected load exceeds the inverter's limit while in on-grid mode.
What to do
Check whether the load power exceeds the limit; otherwise seek help from FoxESS.
- Eps Over Load
EPS Overload (Off-Grid)
The connected backup/EPS load exceeds the inverter's limit while in off-grid mode.
What to do
Check whether the EPS load power exceeds the limit; otherwise seek help from FoxESS.
- Bat Power Low
Battery Power Low
The battery state of charge / available power is low.
What to do
Wait for the battery to be recharged; otherwise seek help from FoxESS.
- PvCon Dir Fault
PV Connection Reversed
The PV string polarity is connected the wrong way round.
What to do
Check that the positive and negative poles of the PV are correctly connected; otherwise seek help from FoxESS.
- BatCon Dir Fault
Battery Connection Reversed
The battery polarity is connected the wrong way round.
What to do
Check that the positive and negative poles of the battery are correctly connected; otherwise seek help from FoxESS.
- Meter Lost Fault
Meter Communication Lost
Communication between the energy meter and the inverter has been interrupted.
What to do
Check that the communication cable between the meter and the inverter is correct and well connected.
- BMS Lost
BMS Communication Lost
Communication between the battery BMS and the inverter has been interrupted.
What to do
Check that the communication cable between the BMS and the inverter is correct and well connected.
- Bms Int Fault
BMS Internal Fault
DIP switch in the wrong position, or communication between battery packs is interrupted.
What to do
Move the DIP switch to the correct position; check that the communication cable between battery packs is correct and well connected.
- Bms Volt High
Battery Over-Voltage (BMS)
The battery BMS reports an over-voltage condition.
What to do
Contact the battery supplier.
- Bms Volt Low
Battery Under-Voltage (BMS)
The battery BMS reports an under-voltage condition.
What to do
Contact the battery supplier.
- Bms ChgCur High
Battery Charge Over-Current (BMS)
The battery BMS reports a charge over-current.
What to do
Contact the battery supplier.
- Bms DchgCur High
Battery Discharge Over-Current (BMS)
The battery BMS reports a discharge over-current.
What to do
Contact the battery supplier.
- Bms Temp High
Battery Over-Temperature (BMS)
The battery BMS reports an over-temperature condition.
What to do
Contact the battery supplier.
- Bms Temp Low
Battery Under-Temperature (BMS)
The battery BMS reports an under-temperature condition.
What to do
Contact the battery supplier.
- 1030
AC Overcurrent
The AC output current has exceeded the safe limit (R-series three-phase string inverter).
What to do
The inverter will reconnect after the grid is restored. If the fault recurs, contact FoxESS Customer Service.
- 1034
DC Component Current Fault
A DC component has been detected in the output current beyond limits.
What to do
Wait for the inverter to return to normal; if it recurs, turn off AC and DC switches, wait 10 minutes, then restart; otherwise contact FoxESS Customer Service.
- 1035
Leakage Overcurrent Fault
Excessive leakage (residual) current, often caused by high parasitic capacitance in poor light or moist conditions.
What to do
Once the environment improves the inverter reconnects; if the environment is normal, check insulation of AC and DC cables; otherwise contact FoxESS Customer Service.
- 1040
Grid Voltage Imbalance
Imbalance between the grid phase voltages (three-phase R-series).
What to do
Inverter reconnects after grid is restored; if it recurs, check protection parameter settings in the app, measure actual grid voltage/frequency per phase and contact the power company; otherwise contact FoxESS Customer Service.
- 1042
Grid High Frequency
Grid frequency above the permitted limit (R-series 'Grid High Freq').
What to do
Inverter reconnects after grid is restored; if it recurs, check protection settings and measure actual grid frequency, contact power company; otherwise contact FoxESS Customer Service.
- 1043
Grid Low Frequency
Grid frequency below the permitted limit (R-series 'Grid Low Freq').
What to do
Inverter reconnects after grid is restored; if it recurs, check protection settings and measure actual grid frequency, contact power company; otherwise contact FoxESS Customer Service.
- 1044
Grid Phase Voltage Over-Limit
A grid phase voltage has exceeded its limit (R-series 'Grid Phase Volt Over-limit').
What to do
Inverter reconnects after grid is restored; if it recurs, check protection settings and measure actual grid voltage, contact power company; otherwise contact FoxESS Customer Service.
- 1045
Grid Line Voltage Over-Limit
A grid line (phase-to-phase) voltage has exceeded its limit (R-series 'Grid Line Volt Over-limit').
What to do
Inverter reconnects after grid is restored; if it recurs, check protection settings and measure actual grid voltage, contact power company; otherwise contact FoxESS Customer Service.
- 1051
Grid Phase Lost Fault
A grid phase has been lost on the three-phase supply.
What to do
Inverter reconnects after grid is restored; if it recurs, measure actual grid voltage and check each phase meets grid-tied requirements, contact power company; otherwise contact FoxESS Customer Service.
- 1066
DC Input MPPT1 Reverse Fault
The PV string on MPPT1 has reversed polarity.
What to do
Check whether the positive and negative polarities of the affected string are reversed; if so, correct them when string current is low; otherwise contact FoxESS Customer Service.
- 1099
Over-Temperature Protection
The inverter has triggered over-temperature protection.
What to do
Check if the inverter is in direct sunlight and shade it; check and clean the air outlet; check the app for a fan alarm; otherwise contact FoxESS Customer Service.
- 1116
Ground Impedance Fault
Abnormal ground (earth) impedance detected.
What to do
Check the ground cables are connected properly and that insulation between ground and live cables is good; otherwise contact FoxESS Customer Service.
- 1123
Grid Relay Fault
Fault in the grid relay.
What to do
Wait for the inverter to return to normal; if it recurs, turn off AC and DC switches, wait 10 minutes, restart; otherwise contact FoxESS Customer Service.
- 1124
Insulation Resistance Low Fault
PV array insulation (ISO) resistance to ground is too low.
What to do
Check the ISO impedance protection value in the app meets local regulations; check DC cable and ground contact; if cables are normal and it occurred on a wet day, re-check in better weather.
- 1145
Arc Fault
An arc fault has been detected on the DC side (AFCI protection).
What to do
Disconnect the DC input and check for damaged cables, loose terminals/fuses and burn marks; reconnect and clear the arc fault in the app; if it persists, contact FoxESS Customer Service.
- 1188
AC SPD Abnormality
The AC surge protection device (SPD) is abnormal.
What to do
Check the status of the SPD and contact FoxESS Customer Service.
- 1189
DC SPD Abnormality
The DC surge protection device (SPD) is abnormal.
What to do
Check the status of the SPD and contact FoxESS Customer Service.
- 1191
External Fan Alarm
The external cooling fan has alarmed, e.g. blocked by debris.
What to do
Check whether the fan is blocked by foreign objects and remove them; contact FoxESS Customer Service.
- 1193
EEPROM Read-Write Alarm
Internal communication / EEPROM read-write abnormality.
What to do
Internal communication is abnormal; turn off AC and DC switches, wait 10 minutes, restart; if it persists, contact FoxESS Customer Service.
- 1313
DC Input MPPT1 Voltage High Fault
The DC input voltage on MPPT1 is too high.
What to do
Wait for the inverter to return to normal; if it persists, contact FoxESS Customer Service.
- 1345
String1 Warning
A warning for PV String 1 (e.g. unreliable connection or a damaged DC fuse).
What to do
Confirm the relevant MPPT is reliably connected (ignore if no connection needed); check whether the string DC fuse is damaged and replace it; otherwise contact FoxESS Customer Service.
Sources
- FoxESS H1(G2)/AC1(G2) Series User Manual V1.0.8 (official)
- FoxESS R-Series (R75/R100/R110) User Manual (official)
- FoxESS H3/AC3 Series User Manual (official)
- FoxESS Community Forum — Error Code-1 No Utility, Code-26 Grid Voltage, Code-27 Grid Frequency
- FoxESS Community Forum — Error Code 28, 10 Minute Average Grid Voltage Fault
Frequently asked
- Where do these FoxESS fault codes come from?
- We compile them from publicly available FoxESS inverter documentation and field references, then rewrite each entry in plain English. Solar Analytica is independent and not affiliated with FoxESS.
- Can I clear these faults myself?
- Some clear automatically once conditions return to normal. Anything involving DC isolators, AC switches, wiring or opening the unit is licensed-electrician work — if in doubt, contact your installer rather than working on a live system.
- My exact code isn't listed — why not?
- Firmware and model variants differ, and manufacturers occasionally revise their codes. We document the most common ones; if yours isn't here, check your inverter's manual or ask your installer.
- How current is this reference?
- Last reviewed June 2026. We revise it when the underlying manufacturer documentation changes.
Other inverter fault libraries
Inverter Fault Library
Huawei Inverter Error Codes
Major and minor alarm codes for Huawei SUN2000 residential and commercial inverters, with plain-English causes and field-tested fixes.
Inverter Fault Library
Sungrow Alarm Codes
The complete Sungrow fault reference — string, SH hybrid and battery families — with every alarm number searchable and grouped by root cause.
Inverter Fault Library
Solis Alarm Codes
Solis (Ginlong) inverter alarm codes covering grid, insulation, temperature and hardware faults, with diagnostic next steps.