F18 on a Sunsynk ECCO single-phase hybrid SG05LP1: AC side over current fault (hardware)
Short answer
On a Sunsynk inverter, F18 means: AC side over current fault (hardware). The inverter stops until the fault clears or is reset.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: AC side over current fault (hardware).
Part involved: AC output stage.
When it shows: Hardware AC overcurrent trip.
Likely causes:
- Inrush current; too many items switching on together; heavy surge; overload; voltage fluctuations; component failure.
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: Restart and check it is normal; seek help if persists.
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).
- Check whether a large load (e.g. pump, compressor, EV charger) started at the time; spread out heavy loads on backup circuits.
What the engineer will check
- Check backup and load power vs rating; check for short circuits on load side; inspect AC terminations.
Who to ask for: Qualified electrician / MCS PV 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 5 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026