Grid Volt Fault on a Fox ESS H1 G2 single-phase hybrid inverter: Grid voltage out of range
Short answer
On a Fox ESS inverter, Grid Volt Fault means: Grid voltage out of range. The inverter stops until the fault clears or is reset.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: Grid voltage out of range.
Part involved: grid voltage protection (G98/G99).
When it shows: Measured grid voltage outside country-code limits.
Likely causes:
- Grid voltage outside the configured protection limits (often high local voltage on sunny days with lots of export).
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 reconnects automatically when the 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).
- If it happens on sunny afternoons repeatedly, tell your installer - they can check whether your local voltage is high and involve the network operator (DNO).
What the engineer will check
- Log grid voltage; check AC cable voltage drop/sizing and terminations; verify grid code (UK G98/G99) selected; raise high-voltage complaint with DNO if supply is out of statutory limits (230 V +10%/-6%).
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
- H1(G2)/AC1(G2) Series User Manual ↗ · V1.0.8 · page 46 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026