AC-coupled Fronius GEN24 electrically isolated — Cerbo GX & Quattro II behavior?

DIY
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Behavior of Victron system (Cerbo GX + Quattro II) when AC-coupled Fronius GEN24 is electrically isolated for an extended period

Setup

  • Multiple Quattro II 48/5000 in parallel (single phase)
  • Cerbo GX
  • Pylontech LV Hub + multiple US5000 batteries
  • Multiple MPPT RS 450/200 and MPPT RS 450/100 (DC coupling)
  • Carlo Gavazzi ET112 energy meter via RS485, configured as AC load role

Project context

We are planning to add a Fronius GEN24 Primo 8.0 or 10.0 (single phase, non-hybrid, MG50) as an AC-coupled PV inverter on the AC-Out of the Quattros, following the Victron AC coupling documentation and respecting the Factor 1.0 rule.

The Fronius will be installed in a separate outbuilding (barn), connected to the main AC-Out bus via a dedicated circuit breaker. This breaker may be opened independently — for example during electrical work on that outbuilding — without shutting down the main system. In this scenario, the Fronius would be completely de-energised (no AC supply), therefore powered off and unreachable on the network (no TCP/IP), for an extended period ranging from a few hours to several days.

Note: we are aware that the GEN24 (non-hybrid, standard grid-tie) is anti-islanding by design and will not produce anything without AC present, even with PV connected and sun available.

Questions

  1. Alarms: Does the Cerbo GX generate an alarm when the Fronius becomes unreachable? If so, which alarm exactly, and is it configurable or mutable (severity, delay, disable)?

  2. Quattro behavior: How do the Quattros behave when the Fronius they were configured with suddenly disappears? Do they enter any degraded mode, generate errors, or change their charge/discharge strategy?

  3. Duration and conditions: Does the behavior evolve depending on how long the Fronius has been absent (e.g. 1 hour vs 3 days)? Does it matter whether there is DC PV production from the MPPT RS at the moment of disconnection?

  4. GX display: How is the absence of the Fronius represented on the Cerbo GX graphical overview and in VRM? Does it show as an error, greyed out, or simply disappear?

  5. Full recovery — key question: After an extended absence, when the Fronius is reconnected and powered back up, does the entire system return to normal operation automatically — including AC coupling, frequency shifting, and Cerbo GX monitoring — or is a manual intervention required on the Victron side?

Thanks in advance for any feedback or real-world experience on this scenario.