DC insulation fault detected — ground leakage on PV string or cable. Inverter will not produce until cleared. This is a safety protection. Fault code appears as 18x (residential) or F-Isolation in SetApp.
Common causes
Damaged PV cable insulationWater ingress into MC4 connectorGround fault in PV arrayIncorrect grounding of DC conductors
What to check
STEP 1
Check all DC cables for visible damage, pinch points, or rodent damage. Inspect MC4 connectors for moisture or corrosion.
STEP 2
Test string insulation resistance with a megohmmeter — each string should show >1 MΩ to earth. Identify the affected string via SetApp Device List.
Escalate if
No visible damage, all strings >1 MΩ, fault persists after dry conditions — contact SolarEdge support. Use decision tree se_isolation_fault for full diagnostic path.
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