What Is an Arc Fault (AFCI) on a Solar Inverter?
Of all the things a solar inverter can warn you about, an arc fault is the most important to understand. It is the inverter telling you it detected an electrical arc in the DC wiring, and an arc is a genuine fire hazard. The good news is that the protection that catches it, the AFCI, is doing exactly its job.
What an arc fault actually is
When a connection in your high-voltage DC panel wiring becomes loose, corroded or damaged, electricity can jump across the tiny gap instead of flowing cleanly through it. That jump is an arc, and it burns extremely hot, hot enough to start a fire. It is the same phenomenon as a welding arc, just unwanted and hidden in your rooftop wiring.
What the AFCI does
Modern inverters include an AFCI (Arc-Fault Circuit Interrupter). It listens to the DC side for the distinctive electrical signature of an arc. When it hears one, it shuts the system down and raises an arc-fault code, on Deye and Sunsynk this is F63. That shutdown is a safety feature, not a malfunction.
What causes an arc fault
- A loose or poorly crimped DC connector, most often an MC4, the small plugs that join panel cables. This is by far the most common cause.
- Corrosion or water ingress in a connector or junction box.
- Damaged or chafed cable insulation.
- A connector that overheated before and left a burnt, high-resistance joint.
The safe way to respond
Because this is a fire-safety issue in live DC wiring, the responsible response is not a DIY repair:
- Look for danger signs. Smoke, a burning smell, or scorch and melt marks mean you treat it as an emergency: shut the system down at the isolators if it is safe, keep clear, and get help immediately.
- Do not keep clearing the code. Resetting an arc fault without finding the arc simply re-energises a possible fire hazard.
- Shut the system down following your installer's procedure (AC breaker off, then DC isolator off).
- Call a licensed solar electrician. They will inspect every DC connector and cable, find and fix the arcing joint, and only then clear the fault.
For the brand-specific steps, see the full guide for Deye F63 or Sunsynk F63. And remember that DC solar wiring is live whenever there is daylight, which is exactly why opening connectors is a job for a professional.