- Error code
- OS 79
- Category
- Insulation resistance
- Manufacturer
- KACO
1What the error means
The insulation resistance of the PV generator is being measured. The inverter runs the check before connecting — a normal stage.
On the display or in the monitoring software it appears as OS 79.
2Possible causes
- Moisture in junction boxes, connectors or modules
- Damaged or worn DC cables
- Faulty module
3What to do
- Note whether it appears after rain or early in the morning.
- Measure the insulation resistance of each string to earth.
- Check connectors and junction boxes for moisture.
- If the PV generator is fine, check the inverter's measuring circuit.
4Repair by Aineas
You send the inverter to our lab in Thessaloniki. We diagnose it, inform you of the fault and the cost, and the repair starts only after you approve it. Every inverter is tested under simulated operating conditions before delivery.