Main Relay Open on a Fox ESS H1 G2 single-phase hybrid inverter: The grid relay keeps open
Short answer
On a Fox ESS inverter, Main Relay Open means: The grid relay keeps open. 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: The grid relay keeps open.
Part involved: grid relay.
When it shows: Relay check fails.
Likely causes:
- Grid relay fails to close.
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: Disconnect PV, grid and battery, then reconnect (installer).
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).
What the engineer will check
- Fox manual action: 'Disconnect PV, grid and battery, then reconnect' - this involves DC and battery isolation and is for the installer. Relay faults that persist usually need unit repair/replacement under warranty.
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
- H1(G2)/AC1(G2) Series User Manual ↗ · V1.0.8 · page 49 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026