Sungrow fault 039 Low System Insulation Resistance in the morning or after rain. What now?

Plain explanation

From the Sungrow manual for the SH-RT hybrid: Wait – it may clear when modules dry. Installer checks the ISO protection value in the app is not set too high. The rest of the checklist is below; work through it in order. Installer only: DC and AC work on a live PV system is dangerous, so owners should note the code and call their installer.

Steps from the source

1. Wait – it may clear when modules dry
2. Installer checks the ISO protection value in the app is not set too high
3. Installer measures string/DC cable resistance to ground
4. If it only appears on rainy days, recheck on a dry day
5. Check battery cables/terminals
6. Persists → Sungrow service

Source

Where installers ask this

• DC current leakage to ground detected by the inverter (r/solar)
• reddit.com/r/amberelectric/comments/1sr1ilh/
• reddit.com/r/solar/comments/1nt5mk0/

General guidance based on the manufacturer's manual or the named source. Always follow the current manual for your exact model and your national code. DC and AC electrical work is for qualified installers only. Not affiliated with or endorsed by any brand named; trademarks belong to their owners.