F26 on a Sunsynk ECCO single-phase hybrid SG05LP1: Bus unbalanced fault
Short answer
On a Sunsynk inverter, F26 means: Bus unbalanced fault. The inverter stops until the fault clears or is reset.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: Bus unbalanced fault.
Part involved: DC bus capacitors.
When it shows: Bus imbalance detected.
Likely causes:
- Series capacitor mismatch; damaged inverter bridge IGBT; badly unbalanced split-phase/3-phase loads; DC leakage current.
Is it safe?
| Does the inverter stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
The inverter stops until the fault clears or is reset.
Resetting itself: yes.
Manual reset: Wait and check; restart 2-3 times; 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
- Check load balance (3-phase), DC leakage; hardware diagnosis.
Who to ask for: Battery/hybrid installer trained on the specific battery (manufacturer-approved installer).
Certification: Battery and hybrid-inverter DC work: installer trained/approved by the manufacturer; electrical work under BS 7671 by a competent person.
What you might notice
Sources
- Fault Codes Causes & Solutions Version 1.0 ↗ · Version 1.0 · page 7 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026