Arc Fault
Fronius · Symo Advanced
What does 402 mean?
This status code indicates that the internal Arc Fault Circuit Interrupter (AFCI) of the Fronius Primo GEN24 208-240 inverter has detected an electrical arc fault in the DC circuit. Arc faults are serious safety hazards caused by loose connections, damaged cables, or faulty components in the PV array.
Common Causes
- Loose or poor connections in the DC wiring, particularly at MC4 connectors or terminal blocks.
- Damaged PV modules or DC cables, where insulation breakdown can lead to arcing.
- A defective AFCI unit within the inverter, leading to false detections.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Inspect all DC connections, especially MC4 connectors, for proper seating, tightness, and signs of overheating or corrosion.
- 2
Visually inspect all PV modules and DC cabling for any physical damage, such as cuts, abrasions, or signs of rodent damage.
- 3
De-energize the inverter (switch off AC and DC disconnects), wait for 5 minutes, then re-energize to reset the AFCI unit. If the message persists, the inverter may require service.