Solar & Off-Grid Power Systems Troubleshooting
Photovoltaic arc-fault protection, grid synchronization impedance faults, transformerless leakage current alarms, and hybrid battery inverter error codes.
Manufacturers & Brands
OEM hardware vendors indexed under Solar Inverters
Deye
Hybrid solar inverters, low-voltage battery storage, and microinverters.
Enphase Energy
Enphase IQ8 microinverters with Sunlight Jumpstart grid-forming technology, Envoy communications gateway, and IQ Battery 5P telematics.
Fronius
High-efficiency SnapINverter and GEN24 Plus hybrid solar systems.
GoodWe
GoodWe ET Series high-voltage hybrid inverters, UPS-level 10ms power transfer switching, and SEMS smart energy management.
Growatt
Global residential and commercial inverter manufacturer with off-grid and hybrid energy storage units.
Huawei FusionSolar
High-efficiency commercial and residential smart string inverters.
SMA Solar
German manufacturer of Sunny Boy and Sunny Island series inverters.
SolarEdge
SolarEdge HD-Wave single phase string inverters, DC power optimizers with module-level MPPT, and StorEdge battery interface telemetry.
Sungrow
Sungrow commercial string inverters and SH residential 3-phase hybrid inverters with built-in DC arc-fault circuit interrupter (AFCI).
Victron Energy
Rugged off-grid and marine MultiPlus inverters, Cerbo GX, and SmartSolar MPPTs.
Indexed Fault Guides in Solar Inverters
Machine-verified error code diagnostic walkthroughs
DC Isolation Resistance Low
Error 18x8F indicates that the inverter's Residual Current Monitoring Unit (RCMU) detected an insulation resistance between the DC PV array conductors and protective earth (PE) below the safety threshold (typically <600kΩ on residential systems). The inverter halts grid injection to prevent electric shock or fire hazards.
DC Resistance Low Isolation Fault
The IQ8+ microinverter has detected an insulation resistance fault between the DC input conductors (PV module positive or negative leads) and equipment ground that falls below the 1000 kΩ (1 MΩ) safety threshold. To prevent electrical shock, arc faults, and fire hazards, the microinverter shuts down its DC-AC H-bridge conversion and logs an active isolation event until DC impedance integrity is re-established.
IQ8 DC Isolation Fault
The microinverter detected that DC insulation resistance between the PV module leads and equipment ground fell below the mandatory threshold (typically < 1000 kΩ / 1 MΩ), indicating a ground fault or moisture ingress on the DC circuit, which trips internal safety isolation to inhibit power generation.
Insulation Resistance Fault
The inverter detected an insulation resistance (Riso) fault on the DC side dropping below the safety threshold (typically < 200 kOhm to ground) during pre-grid connection checks or operational residual current monitoring, preventing grid feed-in to avert ground fault and shock hazards.
DC Isolation Leakage Current Fault
Error 18xBD indicates an RISO/isolation fault where the DC bus isolation resistance to earth has dropped below the safety limit (typically <600 kΩ for single-phase or <1 MΩ for three-phase), causing an excessive residual/leakage current detection prior to grid connection.
DC Isolation Resistance Low
The inverter detected an insulation breakdown between the active DC conductors (PV array or battery circuit) and Protective Earth (PE). Measured isolation resistance fell below the mandatory threshold (typically < 600 kΩ for single-phase or < 1 MΩ for three-phase systems), tripping ground-fault protection to prevent electrical shock and arc hazards.
AFCI DC Arc Lockout
The inverter's internal Arc-Fault Circuit Interrupter (AFCI) detected high-frequency electrical noise characteristic of a series or parallel DC arc fault. Per UL 1699B safety standards, the inverter ceased power generation and engaged a permanent software lockout until manually inspected and cleared.
DC Arc Fault Detected
The integrated Arc Fault Circuit Interrupter (AFCI) detected high-frequency electrical noise characteristic of an electric arc in the DC string circuit (UL 1699B compliance). The inverter has ceased power export and opened internal safety contactors to prevent thermal escalation or fire hazard.
Isolation Fault Low DC Resistance
Error 18x8B indicates the inverter's Residual Current Monitoring Unit (RCMU) detected an insulation resistance between the DC string conductors and Earth ground lower than the threshold (typically <600kΩ to 1MΩ). The inverter automatically disconnects from the grid to prevent leakage currents and electric shock hazards.
RCMU Residual Current Limit Exceeded
State 1030 triggers when the internal Residual Current Monitoring Unit (RCMU) detects leakage current exceeding statutory thresholds (typically >30mA continuous or sharp differential spikes up to 300mA) flowing to ground, disconnecting the inverter from the grid to prevent electric shock or fire.
Excessive Ground Leakage Current Trip
Alarm 2064 triggers when the inverter's internal Residual Current Monitoring Unit (RCMU) detects continuous or surging leakage current (Idc/Iac) to protective earth exceeding safety thresholds (typically >300 mA surge or sustained >30 mA difference), characteristic of parasitic capacitance discharge or isolation degradation in transformerless topologies.
DC Overvoltage MPPT Transient Surge
Fault 008 indicates that the DC input voltage on one of the MPPT trackers exceeded the hardware safety threshold (typically 1000V DC absolute max) or experienced an abrupt transient spike, triggering an immediate shutdown to protect the internal DC-DC boost stage and power capacitors.
Relay Test Fault Error 11
Victron Error 11 occurs when the inverter-charger's internal grid backfeed protection check fails during connection sequence. Before closing internal transfer contacts, the MultiPlus-II measures potential across the safety relays; if voltage is detected when the relays are commanded open or if contact welding is sensed, the unit trips to prevent dangerous islanding.
DC Bus Bar Overvoltage Fault
Error F56 indicates that the internal intermediate DC busbar voltage has exceeded the maximum safety threshold (typically exceeding 800V DC on low-voltage battery architecture hybrid platforms). The DSP firmware engages hardware protection, instantly disabling IGBT gate pulses to prevent capacitor burst or semiconductor breakdown.
Transient Leakage Current Fault
Error 201 indicates the internal Residual Current Monitoring Unit (RCMU) detected an excessive transient leakage current (residual current spike typically >30mA or sudden jump >30mA to ground) exceeding safety limits defined in DIN VDE 0126-1-1 / IEC 62109-2, causing the inverter to immediately disconnect from the grid.
Grid Inverter Hardware Overcurrent
Error F13 indicates that the inverter hardware protection circuit detected an instantaneous AC current spike exceeding the safe threshold during a grid-tied operational mode transition, tripping the IGBT driver protection latch.
Internal DSP Sampling Inconsistency Fault
Error 102 indicates a hardware sampling inconsistency between the master and slave Digital Signal Processors (DSP) or redundant analog-to-digital converter (ADC) channels. The safety supervisor detected a divergence in internal voltage/current telemetry across the internal bus, tripping redundant safety shutdown relays.
Ground Current N-PE Bonding Fault
VE.Bus Error 8 indicates that the internal grounding relay test failed prior to inverter connection or an unexpected current is circulating between Neutral and PE. MultiPlus-II monitors N-PE integrity to ensure safety during transition between grid-tied and islanded mode.
Auto Test PV Isolation Low
Error 407 triggers when the inverter's internal diagnostic test detects that the insulation resistance between the DC PV array conductors and earth is below the safety threshold (typically <50 kΩ or standard local limit), preventing grid synchronization to avoid electrical shock or ground-fault fires.
GFCI Leakage Current Trip
Error F18 indicates that the residual current monitoring unit (RCMU/GFCI) detected an AC or DC leakage current to ground exceeding the safety limit (typically >30mA continuous or >300mA instantaneous spike), triggering an emergency disconnect from the grid.
Deye F24 Grid Relay Failure
Error F24 indicates an internal grid relay self-test failure. During pre-synchronization or disconnection routines, the digital signal processor (DSP) senses an abnormal state across the AC grid safety contactors—such as welded/shorted contacts, open drive coils, or a corrupted voltage feedback signal across the relay bridge.
Inverter Soft Start Failure
Fault 04 trips when the inverter's DC-to-AC conversion stage fails to ramp up the AC output voltage to target operating parameters (230VAC) within the designated soft-start window. This safety mechanism protects the power conversion board from destructive overcurrent events typically caused by high inrush loads connected during startup, an external AC short circuit, or failed internal H-bridge power switches.
Inverter/Charger Temperature Too High
Victron Error 17 (or flashing Temperature LED) triggers when internal power transformers or FET heat sinks reach thermal shutdown thresholds, reducing continuous power to preserve hardware integrity.
AC Over Current Fault
Fault F18 occurs when instantaneous AC output current exceeds the hardware peak current threshold, indicating a downstream short circuit, heavy inrush current, or internal inverter bridge failure.
Bus Voltage Too High
Error Code 08 represents an internal DC bus over-voltage condition (exceeding 500VDC internally). This is a critical protective shutdown to protect the main capacitor bank and IGBT bridge from catastrophic rupture.
Grid Over Frequency Fault
Fault F13 indicates that the utility grid or generator frequency has exceeded the country-code safety limits (typically 50.5Hz or 51.5Hz for 50Hz grids, or 60.5Hz for 60Hz grids).
Heatsink Over Temperature
Error Code 02 triggers when internal thermal sensors register temperatures exceeding 90°C (194°F) on the main power MOSFET heatsink or transformer core.
Low Battery Voltage
Error Code 04 indicates that the battery bank voltage has plummeted below the low-voltage cutoff threshold configured in the inverter settings, prompting an emergency shutdown to prevent irreversible battery cell degradation.