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← Fault codes
Hybrid inverter

EG4 18kPV / 12kPV Hybrid

EG4 shows named faults on the LCD rather than numbered codes. A red dot beside the item means the fault is active; grey means it cleared but is still logged.

Faults — the unit stops (24)
M3 Rx failure. Fault. The M3 microprocessor stopped receiving data from the DSP. Internal comms, not your wiring.
Check first
  1. Power cycle the inverter fully — battery, PV, and AC all down, then back up in order.
  2. If it returns, it is an internal board fault. Open a ticket with the distributor; do not keep resetting it.
Model fault. Fault. The unit is reporting an invalid model value to itself. Firmware or board-level.
Check first
  1. Restart. If it persists, the unit needs the supplier — nothing field-serviceable here.
EPS short circuit. Fault. Do not just reset. A short was detected across the load output terminals.
Check first
  1. Kill everything and verify L1, L2, and N landing correctly on the LOAD terminals — a swapped neutral reads as a short.
  2. Open the load breaker. If the fault clears with the load disconnected, the short is downstream in the subpanel, not in the inverter.
  3. If it faults with nothing connected, the unit is bad.
EPS power reversed. Fault. Power is flowing backwards into the load terminal.
Check first
  1. Confirm nothing is backfeeding the LOAD side — a generator or a second inverter wired to the wrong terminal will do this.
  2. Restart. If it persists with the load side dead, contact the supplier.
Bus short circuit. Fault. Do not just reset. The internal DC bus is shorted. Hardware.
Check first
  1. Do not keep resetting this. Shut down and call the supplier.
Relay fault. Fault. An internal transfer relay is not behaving as commanded.
Check first
  1. Restart once. A relay that will not pass self-test is a return, not a repair.
M8 Tx failure. Fault. The DSP is not receiving data from the M8 microprocessor. Internal.
Check first
  1. Full power cycle. Check for a firmware mismatch after any partial update.
  2. Persistent means supplier.
M3 Tx failure. Fault. The DSP is not receiving data from the M3 microprocessor. Internal.
Check first
  1. Full power cycle.
  2. Persistent means supplier.
Vbus over range. Fault. Do not just reset. Internal DC bus voltage climbed out of range. Usually driven by PV input, but not always — the bus is fed by battery too.
Check first
  1. Measure actual string Voc at the terminals with a meter, cold, first thing in the morning. Do not trust the design number.
  2. Confirm every string is inside the 100–600 V input window and under the 550 V MPPT high-protection trip.
  3. If the array is off and it still faults, look at the battery side before you blame PV.
EPS connect fault. Fault. Do not just reset. The LOAD and GRID terminals appear to be swapped or miswired.
Check first
  1. Trace both terminal blocks. Grid feeds GRID, subpanel lands on LOAD. Getting this backwards can energize the wrong side.
  2. Verify before re-energizing.
PV volt high. Fault. Do not just reset. String voltage exceeded the inverter's PV input limit. This is the fault that kills inverters.
Check first
  1. Measure Voc on every string with the array cold. Correct it to your record low temperature.
  2. Compare against 600 V absolute. Anything over is a design error, not a glitch.
  3. If the string is legal and this keeps firing, the input stage may already be damaged. Do not just clear it.
Hard over curr. Fault. Hardware-level overcurrent protection tripped.
Check first
  1. Restart once. Repeated hardware overcurrent trips mean the unit goes back.
Neutral fault. Fault. Do not just reset. More than 30 V measured between neutral and ground.
Check first
  1. Find the ground-neutral bond. There must be exactly one, at the first service disconnect — the 18kPV never creates one itself.
  2. A floating neutral, a bonded generator, or a bonded RV plug will all do this.
  3. Measure N-G at the panel and at the inverter.
PV short circuit. Fault. Do not just reset. A short was detected on a PV input.
Check first
  1. Disconnect every string. Ring out each one for a positive-to-negative short and a conductor-to-ground short.
  2. A pinched conductor under a rail or a wet, unseated MC4 is the usual culprit.
  3. If it faults with all strings off, the unit is bad.
Temperature fault. Fault. Heat sink temperature exceeded the safe limit.
Check first
  1. Check the clearances — the manual calls for 7.9 inches of free space on all four sides.
  2. Get it out of direct sun. An inverter cooking on a south wall derates and then faults.
  3. Clear debris from the heat sink and confirm the fans spin.
  4. If ambient and clearance are fine, an internal NTC connector may be loose.
Bus sample fault. Fault. The inverter measured DC bus voltage below its PV input voltage, which is not physically sensible. Sensor or board.
Check first
  1. Restart. Persistent means supplier.
Inconsistent. Fault. The DSP and the M8 microprocessor disagree about what the grid voltage is.
Check first
  1. Restart. If the two processors keep disagreeing, the unit needs service.
M8 Rx fault. Fault. The M8 microprocessor is not receiving data from the DSP. Internal.
Check first
  1. Full power cycle. Persistent means supplier.
Para Comm error. Fault. Parallel communication between inverters failed.
Check first
  1. Reseat the parallel cable at both ends. It must be a straight-through CAT5 or better.
  2. Check the CAN termination DIP switches: ON at the first and last inverter in the chain, OFF for everything between.
Para master loss. Fault. No Master is present in the parallel group.
Check first
  1. Set exactly one inverter to '1 phase Master'. Everything else is a Slave.
  2. A single-unit system still has to be set as '1 phase Master' — this catches a lot of people.
Para rating Diff. Fault. The paralleled inverters do not all have the same power rating.
Check first
  1. You cannot parallel mismatched ratings. Confirm every unit is the same model.
Para Phase set error. Fault. The phase setting in the parallel group is wrong.
Check first
  1. Verify the parallel wiring first, then connect each unit to the grid — the system detects phase sequence on its own and usually clears this.
  2. If it persists after grid connection, the wiring is wrong, not the setting.
Para Gen in Accord. Fault. Some inverters in the parallel group see a generator and some do not.
Check first
  1. Either every inverter gets the common generator output, or none of them do. No mixing.
Para sync loss. Fault. The parallel group lost its synchronization trigger signal.
Check first
  1. Restart the group. Recheck the parallel cable and termination before you blame the unit.
Alarms — it may keep running (23)
Bat com failure. Alarm. The inverter cannot talk to the battery BMS. It will fall back to guessing state of charge from voltage, which on a flat LFP curve is nearly useless.
Check first
  1. Check the RJ45 pinout end to end. On the inverter side, CAN H is pin 4 and CAN L is pin 5; RS485 B is pin 1 and A is pin 2.
  2. Confirm the correct Lithium brand is selected in Advanced settings — for EG4 batteries choose Lithium, then brand '1'.
  3. LifePower4 V1 batteries need a firmware update before closed-loop comms will work at all.
  4. The comm cable must land on the master battery, not a slave.
AFCI com failure. Alarm. The inverter lost communication with its arc-fault detection module.
Check first
  1. Restart. If it does not come back, the AFCI board is a supplier issue — and you are running without arc-fault protection until it is fixed.
AFCI high. Alarm. Do not just reset. An arc fault was detected on the DC side. Treat this as real until proven otherwise.
Check first
  1. Do not simply clear and walk away. An arc fault is a fire in progress somewhere.
  2. Check every MC4 on the roof. A connector that was never fully seated, or a cross-mated pair from two different brands, is the overwhelming cause.
  3. Measure Voc and Isc on each string and compare against expected.
  4. Only clear the alarm after you have physically inspected the DC path.
Meter com failure. Alarm. The inverter cannot reach the energy meter.
Check first
  1. Check the meter comm cable and its terminations. Restart.
  2. Confirm the meter is actually powered.
Bat Fault. Alarm. Do not just reset. The battery is refusing to charge or discharge.
Check first
  1. Check the comm cable pinout at both ends.
  2. Verify the correct battery brand is selected in the inverter.
  3. Look at the battery's own indicator. If the BMS is faulting, this is a battery problem, not an inverter problem — call the battery supplier.
  4. Cold is a common cause. A BMS will block charging below freezing, exactly as it should.
LCD com failure. Alarm. The display cannot talk to the M3 microprocessor.
Check first
  1. Restart. The inverter may still be running correctly with a dead screen — check the monitor portal.
Fwm mismatch. Alarm. The microprocessors are running mismatched firmware versions.
Check first
  1. Re-run the firmware update, start to finish. A partial update leaves the processors out of step.
  2. Never interrupt an update. If it failed, restart it from the first task.
Fan stuck. Alarm. A cooling fan is not turning, or is turning too slowly.
Check first
  1. Kill power and look for debris, a wasp nest, or a seized bearing.
  2. A stuck fan becomes a temperature fault under load. Fix it before summer.
Trip by GFCI high. Alarm. Do not just reset. Leakage current detected on the AC side.
Check first
  1. Look for a ground fault on both the grid and load sides. Do not assume it is nuisance.
  2. Moisture in a junction box and a conductor pinched under a rail are the two classics.
  3. Restart only after you have inspected. If it trips again, stop resetting it.
Trip by dci high. Alarm. The inverter measured excessive DC injection into the grid terminal.
Check first
  1. Restart. Persistent DC injection is a hardware fault and a utility compliance problem — contact the supplier.
PV short circuit. Alarm. Do not just reset. A short was detected on the PV input.
Check first
  1. Disconnect strings and ring each one out individually.
  2. Restart after the DC side is proven clean.
GFCI module fault. Alarm. The ground-fault detection module itself is misbehaving.
Check first
  1. Restart. If it stays faulted you are running without ground-fault protection — get it serviced.
Bat volt high. Alarm. Do not just reset. Battery voltage is above the inverter's window.
Check first
  1. Measure the pack. Anything above roughly 59.9 V on a 48 V nominal system is out of spec.
  2. Check the charge voltage settings against the battery manufacturer's numbers, not the inverter's defaults.
  3. A BMS that has stopped balancing will push one cell group high.
Bat volt low. Alarm. Do not just reset. Battery voltage is below the inverter's window.
Check first
  1. Measure the pack. Below roughly 40 V on a 48 V nominal system is out of spec.
  2. Check the low-voltage cutoff and the on-grid and off-grid discharge cutoffs.
  3. A deeply discharged LFP pack may need the BMS woken up before it will accept charge.
Bat open. Alarm. The inverter cannot see the battery at all.
Check first
  1. Check the battery breaker and any fuse in the DC path.
  2. Confirm the DC disconnect is closed and the pack's own breaker is on.
  3. Reconnect in the right order — battery breakers closed before the BMS pre-charges.
Off-grid overload. Alarm. The load on the backup output exceeds what the inverter can carry.
Check first
  1. Total up what is actually on the LOAD subpanel. Continuous rating is 12 kW at 240 V.
  2. Motor inrush is the usual trigger. A soft start on the compressor is cheaper than a bigger inverter.
  3. Shed loads or re-split the backup panel.
Off-grid overvolt. Alarm. Backup output voltage is too high.
Check first
  1. Restart. Persistent overvoltage on the load output is a supplier issue — do not leave loads connected.
Meter reversed. Alarm. The meter or CT connection is backwards.
Check first
  1. Check the CT arrows — they must point toward the inverter, CT1 on L1 and CT2 on L2.
  2. There is a 'CT direction reversed' checkbox in Advanced settings, but fix the physical install first.
  3. A backwards CT will happily charge the battery from the grid all night.
Off-grid dcv high. Alarm. Too much DC component measured on the backup output while running off grid.
Check first
  1. Restart. Persistent means supplier.
RSD Active. Alarm. Rapid shutdown has been initiated. This is the system doing its job.
Check first
  1. Check whether the RSD or E-Stop button is pressed or latched.
  2. On EG4 batteries in closed-loop comms, RSD also triggers the ESS disconnect, so the battery will drop too.
  3. Reset the button, then restart.
Para phase loss. Alarm. A phase is missing in the parallel group.
Check first
  1. Verify the wiring at every inverter.
  2. A 3-phase Master needs at least 3 inverters; a 2x208 Master needs at least 2. Grid L1, L2, and L3 must land correctly on each.
Para no BM set. Alarm. No Master has been set in the parallel group.
Check first
  1. Set exactly one inverter as Master.
Para multi BM set. Alarm. More than one Master has been set in the parallel group.
Check first
  1. Two or more units are claiming Master. Keep one, set the rest to Slave.
Source: EG4 18kPV user manual, v2.7.5, sections 12.3-12.4. Firmware and manual revisions change these tables. Confirm against the manual for the unit in front of you before you act.