F55 on a Sunsynk ECCO single-phase hybrid SG05LP1: DC voltage high fault - BUS voltage too high
Short answer
On a Sunsynk inverter, F55 means: DC voltage high fault - BUS voltage too high. The inverter stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: DC voltage high fault - BUS voltage too high.
Part involved: PV input / DC bus.
When it shows: DC bus over-voltage.
Likely causes:
- PV string input voltage too high; bus capacitor damaged; battery voltage too high.
Is it safe?
| Does the inverter stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The inverter stops until the fault clears or is reset.
Resetting itself: unknown.
Manual reset: Check battery and PV voltages; seek help.
What you can check
- Read the full code and message on the inverter screen or in the Sunsynk Connect app and note the date/time for your installer.
- Check the inverter's AC isolator next to the inverter and the solar/battery breaker in the consumer unit are ON (do not reset a breaker that trips again - call your installer).
What the engineer will check
- Measure PV Voc and battery voltage; check string design.
Who to ask for: MCS-certified solar PV installer (DC/string work) or the original installer.
Certification: Work on DC strings and inverter enclosures: competent PV installer (MCS-certified installer for warranty/SEG continuity); electrical work notifiable under Part P (England & Wales) or equivalent.
What you might notice
Sources
- Fault Codes Causes & Solutions Version 1.0 ↗ · Version 1.0 · page 11 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026