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Fox ESS inverter error codes, the full list
Fox ESS hybrid inverters (H1, AC1, AIO, KH and T-series) show faults as named alarm messages like Grid Lost Fault or BMS Lost on the screen and in the FoxCloud app under Current Alarms. Some series also show a numeric Error N that maps to the same message. Find your fault below, see how urgent it is, and open the step-by-step fix. Start by typing it:
| Code | What it means | Urgency | Fix |
|---|---|---|---|
| Grid Lost Fault | No utility grid detected | Self-clears | Full fix guide → |
| Grid Volt Fault | Grid voltage out of range (Error 26) | Self-clears | Full fix guide → |
| Grid Freq Fault | Grid frequency out of range (Error 27) | Self-clears | Full fix guide → |
| 10min Volt Fault | 10-minute average grid voltage too high (Error 28) | Self-clears | Full fix guide → |
| Bat Volt Low | Battery charge/voltage too low | Self-clears | Full fix guide → |
| BMS Lost | Lost communication with the battery BMS (Error 14) | Check & restart | Full fix guide → |
| Meter Lost Fault | Lost communication with the meter/CT (Error 242) | Check & restart | Full fix guide → |
| Temp Fault | Inverter over temperature | Check & restart | Full fix guide → |
| Bat Over Temp | Battery temperature out of range | Check & restart | Full fix guide → |
| PV Volt Fault | PV string voltage out of range (Error 17) | Check & restart | Full fix guide → |
| Bat Volt Fault | Battery voltage out of range (Error 194/198) | Check & restart | Full fix guide → |
| SW Bus Vol Fault | Internal DC bus voltage out of range | Check & restart | Full fix guide → |
| Over Load Fault | Demand exceeds the inverter rating | Check & restart | Full fix guide → |
| Iso Fault | Low PV insulation to earth (Error 3) | Check & restart | Full fix guide → |
| Res Cur Fault | Excess earth-leakage current (RCD) | Stop, call a pro | Full fix guide → |
| DCI Fault | DC injected into the AC output too high | Stop, call a pro | Full fix guide → |
| Arc Fault | DC arc detected (AFCI), fire risk | Stop, call a pro | Full fix guide → |
| M1 Close Fault / M2 Close Fault | Grid relay stuck or welded | Stop, call a pro | Full fix guide → |
| PvCon Dir Fault | PV polarity reversed (Error 15/16) | Stop, call a pro | Full fix guide → |
| Inv EEPROM Fault | Inverter memory corrupted | Stop, call a pro | Full fix guide → |
| Bms HW Protect | Battery BMS hardware protection tripped (Error 211) | Stop, call a pro | Full fix guide → |
| Communication Fault (Master/Manager) | Internal master-manager comms lost (Error 11) | Stop, call a pro | Full fix guide → |
Reading the fault on your Fox ESS
The alarm shows on the inverter's LCD and in the FoxCloud app and web portal under Current Alarms / History. Note the exact message (and any Error number) and whether it cleared on its own before you start.
How to read the urgency rating
Self-clears usually a passing grid or weather event; the inverter reconnects itself.
Check & restart do a few safe checks and a proper power cycle.
Stop, call a pro a safety or hardware fault; don't keep resetting it.