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Fox ESS Arc Fault

Updated September 2026 · Reviewed for technical accuracy · ~2 min read
🔥 Treat this as a fire hazard. Arc Fault means your Fox ESS detected an electrical arc somewhere in the DC (solar) wiring. Arcing produces intense heat and can start a fire. Do not reset the alarm or restart the system, and do not open or touch the DC connectors yourself. The fault must be found and fixed by a qualified installer before the inverter goes back on.

Arc Fault means the inverter's arc-fault detector, the AFCI, sensed a series arc between the PV array and the inverter. Fox ESS lists it on models with AFCI, such as the H3-Plus and P3-Plus (fault code 1145, with 1181 Arc Permanent Fault and 1294 AFCI fault lock device in the same table). On the H1(G2) and AC1(G2), AFCI is optional and the alarm table does not list it. When the AFCI alarm trips, the inverter stops working until the alarm is cleared. This is almost always a real wiring problem, a damaged cable, a loose or corroded connector, or an arcing joint in the array, and it should be taken seriously.

What usually causes it

  • A loose or poorly seated DC connector. An MC4 connector that was not clicked fully home, or has worked loose over time, can arc across the small gap.
  • A corroded or water-damaged connector. Moisture ingress builds resistance and burning at the contact, which the AFCI reads as an arc.
  • A damaged or chafed PV cable. A cable rubbed against a roof edge, chewed by rodents or cracked by UV can arc to itself or to the frame.
  • An arcing joint in the array. A weak crimp, mismatched connector brands or a bad junction inside a combiner can all produce intermittent arcing.

How to handle it safely

  1. Do not clear the alarm. Clearing it before the cause is fixed tells the inverter to re-energise a circuit that may be arcing. Leave the system shut down.
  2. Switch off the DC isolator if you can reach it safely. Turn the DC rotary isolator to OFF to de-energise the strings into the inverter. Do not unplug or open any connector yourself.
  3. Look, do not touch. From a safe distance check for any smell of burning, smoke, scorch marks or discolouration around the connectors and cable runs. If you see or smell burning, keep clear and treat it as an active fire risk.
  4. Call a qualified installer. Have them inspect every PV connector and the full cable run for burns, damage and corrosion. The faulty component must be repaired or replaced before any restart.
  5. Only restart after the fix. The alarm should be cleared by the installer once the damaged part is sorted, not before. A repeat Arc Fault after a clear means the problem is still live.
When to call a professional. Arc Fault is one of the few inverter faults that points at a genuine fire risk, so it always warrants a qualified installer rather than a DIY reset. The PV strings can carry several hundred volts of DC even in weak light, and DC arcs do not self-extinguish the way AC arcs do. Never open live DC connectors, never bypass the AFCI, and do not return the system to service until the arcing source has been found and repaired. If you see smoke or flame, call your local emergency number first.

Related Fox ESS codes

ISO Fault PV Volt Fault PV Connect Direction Fault

FAQ

Can I just clear the Arc Fault and see if it comes back?

No. An arc gives off enough heat to start a fire, so clearing the alarm to test it is not worth the risk. If the AFCI tripped, treat it as a real arc until an installer has checked the connectors and cabling and confirmed the array is safe. Clear it only after the cause is fixed.

Could it be a false alarm rather than real arcing?

Occasionally a marginal connector or electrical noise can trigger the AFCI, but you cannot tell that apart from real arcing by looking at the screen. The only safe assumption is that the arc is genuine. Let a qualified installer inspect the strings, find any damaged or loose connector and decide whether it was a fault or a sensor issue.

Helpful guides

Error codes explained How to safely restart your inverter What is an arc fault

Correction, 25 September 2026: An earlier version cited the H1/AC1 manual and a FoxCloud alarm list for this alarm and listed "Arc Fault Detected" and "AFCI Alarm" as other names. The H1(G2)/AC1(G2) manual does not list Arc Fault; the source is now the H3-Plus/P3-Plus manual, which does.

Sources

  • Fox ESS H3-Plus/P3-Plus user manual, V1.2: section 3.7, AFCI Function (series arc detection between PV array and inverter; the inverter stops working on an AFCI alarm), and the fault table (1145 Arc Fault: check whether the string circuit arcs or is in poor contact, fix it, then clear the fault and restart; 1181 Arc Permanent Fault; 1294 AFCI fault lock device).
  • Fox ESS H1(G2)/AC1(G2) Series user manual, V1.0.8: lists AFCI only as optional in the specifications; Arc Fault is not in its alarm table.
⚠️ Safety disclaimer. Solar inverters carry lethal DC and AC voltage even when "off". Arc Fault signals a possible fire risk in the DC wiring. Do not open DC connectors or restart the system yourself. All PV inspection, repair and restart must be done by a licensed installer or electrician.