SG04LP3/SG05LP1 hybrid families and SG01HP3-EU-DM2
Deye F21 error code
DC bus overcurrent.
Likely causes
- PV input current above the configured setting
- Battery charge/discharge current setting too high
- Bus short or power-stage fault
- Grid surge or backfeed
Checks to run, in order
- 1Check the PV input current and battery current setting
- 2Inspect the DC bus and battery wiring
- 3Restart the system
Fixes
- Reduce the PV and battery current settings
- Restart two to three times
When to escalate
If F21 persists with current within settings, the bus current sensor or power stack needs distributor service.
Fix it with the right tools
Check the system around the fault before replacing parts: load, battery bank, PV string and commissioning settings. If you need a second opinion, send the code and your inverter model to our team.
Before you open the inverter
- Isolate both the AC and DC sides, then confirm the display is dead before touching terminals.
- Use insulated tools and one hand where possible. DC arcs do not self-extinguish like AC.
- If you see burnt terminals, swollen cells, leaking electrolyte or a burning smell, stop and escalate instead of resetting the fault.
Questions installers ask
What does Deye F21 mean?
DC bus overcurrent.
How do I fix Deye F21?
Reduce the PV and battery current settings Restart two to three times
When should I escalate Deye F21?
If F21 persists with current within settings, the bus current sensor or power stack needs distributor service.
Can I reset Deye F21 myself?
Only after isolating the AC and DC sides and running the checks above. If Deye F21 returns immediately, stop resetting it and escalate; a repeating fault usually points to a real circuit, battery or hardware problem.
Which models show Deye F21?
Deye F21 is documented for SG04LP3/SG05LP1 hybrid families and SG01HP3-EU-DM2. Confirm the code on your own unit's display or manual before ordering parts.
More Deye error codes
- Deye F01PV input polarity is reversed at one or both DC inputs.
- Deye F02PV insulation resistance to earth is below the safety limit.
- Deye F03Ground fault detected on the PV array (GFDI).
- Deye F04GFDI ground-failure alarm: the PV array or inverter is not properly earthed.
- Deye F05Control-board EEPROM read failure.
- Deye F06Control-board EEPROM write failure.
Guidance reviewed 17 October 2026 by the Mishka Energy installer team. Error codes vary by brand, model family and firmware; confirm against the manufacturer manual.
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