PLL_ OverTime on a Fox ESS H3 three-phase hybrid inverter: Three-phase system access single-phase AC
Short answer
On a Fox ESS inverter, PLL_ OverTime means: Three-phase system access single-phase AC. The inverter stops until the fault clears or is reset.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: Three-phase system access single-phase AC.
Part involved: 3-phase grid sync (H3).
When it shows: Phase-lock failure.
Likely causes:
- Three-phase inverter connected to (or seeing) a single-phase supply - phase lost.
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: System will reconnect if utility is back to normal.
What you can check
- Read the full code and message on the inverter screen or in the FoxCloud 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 part of the house has lost power (one phase down) - report to the network operator (105) if so.
What the engineer will check
- Check all three phases at inverter; check phase sequence and wiring.
Who to ask for: Installer, with DNO (network operator) if grid supply is at fault.
Certification: None for homeowner checks; any grid-protection setting change needs installer and DNO consent (G98/G99).
What you might notice
Sources
- H3/AC3 Series User Manual ↗ · V1.0.4 · page 57 (H3/AC3 V1.0.4) · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026