Solar · Error codes
What does SMA Event 3501 'Insulation failure' mean on my Sunny Boy?
Short answer
SMA Event 3501 means the inverter has detected an earth (ground) fault in the solar panel wiring, so it stops feeding in. Don't touch the panels, cables or inverter. Note whether it happens after rain, then call your installer to test the insulation of each string. SMA lists 3601 and 3701 as related earth-fault events (manual checked 24 September 2026).
Last checked 24 September 2026 · 1 source
In more detail
- Red LED plus events 3501, 3601 or 3701 indicate a possible ground fault (SMA manual 11.3).
- Common causes: damaged DC cable, water in connectors, module insulation defects.
- Engineer measures insulation resistance per string.
The facts, dated
- 01SMA Sunny Boy event 3501 = Insulation failure / Check generator (ground fault in PV array) — 3501 event
manufacturer · n/a · checked 24 September 2026 · files.sma.de
Sources
- files.sma.de — files.sma.de/downloads/SBxx-1AV-41-BE-en-21.pdf
Last checked: 24 September 2026