The Complete Guide To Fox ESS Inverter Error Codes

The average grid voltage over the last ten minutes was above the limit, so the inverter disconnected as the rules require. It reconnects itself; if it happens most days the street voltage is high and the network may need to be told. The string inverters show it as Grid 10Min OVP; Fox Cloud logs it as Error 28.

The grid frequency went outside the inverter's limits for a moment and it disconnected. It reconnects by itself once the grid is steady. The Fox Cloud app logs this as Error 27.

The inverter cannot see mains power on its AC side. Usually the power is out, the solar supply main switch or breaker in the switchboard is off, or an AC connection is loose; it reconnects by itself once the grid is back. The Fox Cloud app logs this as Error 1 (No Utility).

The mains voltage at the inverter went outside the range it is allowed to export at, so it disconnected. It reconnects by itself; if it happens most sunny afternoons the cable run or the street voltage needs checking. The Fox Cloud app logs this as Error 26. The S, T and F string inverters show it as Grid Voltage Fault.

On the S, T and F string inverters, PLL Fault means the inverter lost its lock on the grid waveform and will reconnect itself when the grid is clean again. On the H3 three-phase hybrids the related message PLL_ OverTime means a three-phase unit is connected to a single-phase supply, which is a wiring or supply matter for the installer.

On the S, T and F string inverters, the grid voltage jumped suddenly for an instant, often a switching event or storm on the network, and the inverter disconnected to protect itself. It normally restarts on its own; if it repeats on calm days the AC connections need checking.

During a blackout the appliances on the backup (EPS) circuit are drawing more than the inverter can supply, often an air conditioner, oven, pump or kettle starting together. Switch off the heavy appliances and it recovers; if it trips with little connected the backup wiring needs checking.

On a hybrid, the household load the inverter is trying to supply while the grid is connected is above what it is rated for, often a large appliance starting. Switch off the heavy appliance and it recovers; if it trips with ordinary loads the settings or the inverter need checking.

The voltage from the panels is outside what the inverter accepts, usually too many panels in one string, which shows up most on cold clear mornings. The string design needs checking by an electrician. The S and F string inverters show it as PV OVP. Over-voltage, over-current and short-circuit faults can damage hardware, so we treat them as a call.

A string from the panels is connected the wrong way round at the inverter. This is a wiring fault and must be corrected by an electrician; do not keep restarting it.

The inverter's arc-fault detector (AFCI) picked up the signature of an electrical arc in the panel wiring, usually a loose or corroded DC connector or a damaged cable. Fox lists it on its three-phase string inverters as code 1145 and the newer hybrids carry AFCI too. An arc is a fire risk, so the DC wiring must be inspected by an electrician before the fault is cleared in the app.

The inverter's two processors each measure the grid voltage, grid frequency, DC injection and leakage current, and their readings do not agree (GridV, GridF, Dci or Rc Cons Fault). The S, F and T string inverters show it as Consistent Fault or Inconsistency. One restart may clear it; if it comes back a measuring circuit has failed and the inverter needs a technician.

The inverter's earth connection is missing or poor, or the voltage between neutral and earth at the inverter is wrong, which usually means an AC wiring problem. The earthing and the AC neutral and earth wiring need an electrician; do not keep restarting it.

The inverter found too little insulation between the solar wiring and earth, usually water in a connector or isolator, a chafed cable or a damaged panel. Morning alarms that clear by midday point to dew; a fault that stays is an electrical safety issue and needs an electrician. Fox Cloud logs it as Error 3.

The inverter measured current leaking to earth from the solar wiring, usually damaged cable insulation, water in a connector, or high humidity. On the S, T and F string inverters the same trip shows as GFCI Fault. Because this is an electrical safety trip, a repeat needs an electrician.

The inverter's own leakage-current sensing circuit has failed its check, as opposed to finding a real leak. If one restart does not clear it the sensor or board inside has failed. On the S, T and F string inverters the matching message is GFCD Fault.

On the fan-cooled T-G3 three-phase string inverters, a cooling fan has stopped or is jammed, often by leaves, dust or a nest. The inverter may keep running but will overheat on hot days until the fan is cleared or replaced. Heat shutdowns point at a failing fan, a blocked vent or a bad installation spot, so we treat them as a call.

The inverter's temperature went over its limit, so it cut back or stopped. Usually it is mounted in direct sun or a hot, closed space; it comes back once it cools, but if it happens on ordinary days the heatsink, fan or mounting spot needs a look. The string inverters show it as Over Temp Fault. Heat shutdowns point at a failing fan, a blocked vent or a bad installation spot, so we treat them as a call.

The inverter is letting a small amount of DC into its AC output, which the grid rules do not allow, so it disconnected. A one-off usually clears with a wait or one restart; if it keeps coming back the output stage or its sensor needs testing. Fox Cloud logs it as Error 132. DC on the AC side is a protection fault, so we treat it as a call.

The relay that switches the backup (EPS) circuit over during a blackout failed its self-test, so backup power will not work until it is fixed. If one restart does not clear it the relay or board has failed.

The relays that connect the inverter to the grid failed their self-test: stuck open (Main Relay Open) or stuck closed (S1, S2, M1 or M2 Close Fault on the H1 and KH; Grid Relay Fault on the H3; Relay Fault on the S and T string inverters). A restart may clear a one-off; a repeat means a relay has failed and the inverter must not keep running, so it needs a technician.

The inverter's hardware protection tripped because the internal DC bus voltage went well outside its range. This is usually a fault inside the inverter; if one restart does not clear it the power board needs a technician.

The inverter's hardware protection tripped on a large output current surge, which is more serious than the software trip. If one restart does not clear it, or it comes back at ordinary loads, the power stage needs testing by a technician.

The inverter's hardware protection tripped on a large current from the panels. Fox's H3 manual says to check the PV positive and negative are connected the right way; if a restart does not clear it the input stage needs testing by a technician.

The inverter's settings memory failed a read or write, on the inverter board (Inv EEPROM Fault) or the manager board (ARM EEPROM Fault). It is often a one-off after a firmware update and a restart clears it; if it comes back the memory or board needs repair. The string inverters show it as EEPROM Fault. Internal and hardware faults need testing with the right instruments, so we treat them as a call.

The circuit the inverter uses to measure voltages and currents has failed its self-check, so the inverter cannot trust its own readings and stops. One restart may clear it; if it comes back the control board has a fault. The S, T and F string inverters show it as Sample Fault.

The two processors inside the inverter (master and slave DSP) have stopped talking to each other. It can recover with one restart; if it comes back the control board needs a technician. The S and T string inverters show it as SPI Fault, the F series as MS Comm Lost.

The inverter has lost contact with the energy meter or CT clamp in the switchboard, so export limiting and the home-use figures in the app stop working and a hybrid may charge or discharge at the wrong times. Usually a loose or damaged meter cable or a setting changed after a firmware update. Fox Cloud logs it as Error 242 (meter) or Error 240 (fail to detect CT). The T-G3 shows it as Meter fault.

The main processor and the manager board inside the inverter have stopped talking to each other. This is not the wifi or app connection. It can recover with one restart; if it comes back the control board or its ribbon cable needs a technician. The F series shows it as Comm Lost; Fox Cloud logs it as Error 11.

On the S, T and F string inverters, the small power supply that runs the inverter's own electronics has failed its check. One restart may clear it; if it comes back the control board needs a technician. Fox Cloud reports a related message on F-series units as Error 191, Auxiliary Power fail.

The voltage on the inverter's internal DC bus went outside its normal range. On hybrids it often appears when the unit switches to backup power or during a forced charge; Fox's H3 manual also says to check the neutral is connected to the GRID port and that the firmware is current. If a restart does not clear it the inverter needs testing. The S and T string inverters show it as Bus Volt Fault.

The inverter's software saw more output current than it allows for an instant, often a heavy appliance starting on the backup circuit or a grid disturbance. It usually clears within a minute; if it repeats with normal loads the inverter needs testing. The S, T and F string inverters show the equivalent as OCP Fault. Over-voltage, over-current and short-circuit faults can damage hardware, so we treat them as a call.

The inverter's software measured more current from a string than it allows, often two strings paralleled into one input or a brief surge. It often clears with one restart; if it repeats the string wiring needs checking against the inverter's input rating. Internal and hardware faults need testing with the right instruments, so we treat them as a call.

The part of the inverter that steps the battery voltage up or down (the boost or buck converter) has failed its check. Fox's H3 manual says Bat Boost Fault can also mean the battery-side relay did not close and that the firmware should be current. If a restart does not clear it the inverter needs a technician.

The battery has reached its minimum charge and the inverter has stopped drawing from it to protect it. This is normal protection, not a fault: it clears once the sun or the grid recharges the battery. If it shows on a sunny day the charge settings need a look.

The relay inside the inverter that connects the battery is stuck open (Bat Relay Open) or stuck closed (Bat Relay Short Circuit), so it failed its self-test. One restart may clear a one-off; a repeat means the relay or board has failed, which is a job for a technician. Stuck closed is the more serious of the two.

The battery voltage the inverter sees is higher or lower than it expects, often a very flat battery, a battery that has switched itself off, or a mismatch between the battery and the inverter's settings. Let it charge if it is just low; if the fault stays the battery, its cables and the settings need checking.

The battery positive and negative appear to be swapped at the inverter. This is a wiring fault that must be corrected by an electrician; do not keep restarting it.

The battery's own management system saw more current flowing in (Bms ChgCur High) or out (Bms DchgCur High) than it allows, often during a heavy backup load or a forced charge. It usually clears on its own; if it repeats the inverter's charge and discharge current settings need matching to the battery. Battery protection faults are not something to ride out at home, so we treat them as a call.

The inverter asked the battery to charge and the battery's management system did not respond. It is usually a communication or software problem between the two rather than a hardware fault; a restart often clears it, and a repeat needs the firmware checked. Internal and hardware faults need testing with the right instruments, so we treat them as a call.

The data link between the battery's management system and the inverter is dropping out, a close cousin of BMS Lost. Usually the battery data cable is loose, damaged or in the wrong port. The cable and ports need checking. Battery protection faults are not something to ride out at home, so we treat them as a call.

The battery's own management system has tripped a hardware protection (Bms HW Protect), found a fault in its own circuitry (BmsCircuit Fault) or in its internal relay (Bms Relay Fault). These are faults inside the battery; do not keep restarting it. Fox says to contact the battery supplier.

The battery's own management system found too little insulation between the battery's high-voltage circuit and earth. This is a different fault from the panel Iso Fault and is an electrical safety issue inside or around the battery; it needs a qualified technician, not a restart.

The battery modules in the stack have stopped talking to each other, or the address (DIP) switch on the battery is in the wrong position, which often happens after a module is added. The installer needs to set the switch and check the cables between the battery modules.

The inverter has lost contact with the battery's management system, usually a loose or damaged battery data (CAN) cable, the cable in the wrong port, a battery that has switched itself off, or on single-battery EP and HV2600 setups the missing terminator or bypass plugs. The battery stops charging and discharging until it is back. Fox Cloud logs it as Error 14.

The battery's own management system reports its cells are too hot and has paused charging or discharging until they cool. Usually the battery is in direct sun or a hot, closed space; it comes back once it cools, but if it happens on ordinary days the location or the battery needs a look. Heat shutdowns point at a failing fan, a blocked vent or a bad installation spot, so we treat them as a call.

The battery's own management system reports its cells are below the temperature it allows charging at, so it is waiting. It clears itself once the day warms; in a cold garage on a winter morning this is normal.

The battery modules in the stack do not match each other: different capacities (Bms Type Unmatch), different software versions (Bms Ver Unmatch, Bms SwHw Unmatch, Bms M&S Unmatch) or different cell makers (Bms Mfg Unmatch). It usually appears after a module is added or a firmware update. The installer needs to align the firmware or the modules; Fox says to contact the battery supplier. Battery protection faults are not something to ride out at home, so we treat them as a call.

The battery's own management system reports its voltage is too high and has paused charging to protect the cells. It often follows a firmware mismatch or cells that need balancing. Fox says to contact the battery supplier; your installer can check the battery firmware and run a supervised balancing charge. Over-voltage, over-current and short-circuit faults can damage hardware, so we treat them as a call.

The battery's own management system reports its voltage is too low and has shut off output to protect the cells, usually a battery that has been run flat and left, for example through a long blackout or a power cut at the switchboard. It needs charging under supervision; Fox says to contact the battery supplier and the installer can check the minimum charge setting. Battery protection faults are not something to ride out at home, so we treat them as a call.

The cells inside the battery are at noticeably different charge levels, so the pack cannot use its full capacity. It can follow a long stretch of partial charging; a few full charge cycles under the installer's supervision often brings it back, but a repeat means a cell or module is failing. Battery protection faults are not something to ride out at home, so we treat them as a call.

A sensor inside the battery that measures voltage (BmsVoltsSen Fault), temperature (BmsTempSen Fault) or current (BmsCurSen Fault) has failed, so the battery cannot protect itself properly and stops. This is a fault inside the battery and needs the supplier or a technician.

The inverter's hardware protection tripped on a large current surge on the battery side, which is more serious than the software trip. If one restart does not clear it the battery connection and the inverter's battery stage need testing by a technician.

Shown on the battery's own lights and in the app: the EP, ECS or HV2600 battery stack could not number its modules at start-up, so the battery will not run. The usual causes are a missing terminator or bypass plug on a single-battery setup, a loose link cable between modules, or a wrong DIP switch. The installer needs to check the plugs, cables and switch settings.

Shown on the battery's own lights and in the app: the EP or ECS battery has lost its data link to the inverter (the PCS), the battery-side view of BMS Lost. Usually the CAN cable between the battery and the inverter is loose, damaged or in the wrong port. The cable and ports need checking.

The inverter's software measured more current flowing to or from the battery than it allows for a moment, often during a heavy backup load or a forced charge. It usually clears with one restart; if it repeats the charge and discharge current settings and the battery need checking.