question

Hi @Robert Boerescu

The setup you've described i believe is just ESS system with AC coupled Fronius solar (connected on ACIN side). Which is like the diagrams in the below link (except you've described it without ac coupled solar on AC OUT side). I've attached the link for further details.

ESS Quick Installation Guide [Victron Energy]

The link explains it better but easysolar will charge the batteries using the solar (AC coupled) from Fronius before exporting to the grid.

ie If you've got any loads on AC IN side of connection fronius will be used to power them, any excess the victron system will detected being exported (EM24) and start charging batteries and balance it so 0 is being export to grid, until batteries are full then any excess power will be export to the grid.

This link should be hopefully be useful in setting up what you're looking for if you've not integrated fronius into victron venus os/cerbogx already

AC-coupled PV with Fronius PV Inverters [Victron Energy]

In regards to how much power easysolar send to ACIN loads without exporting to grid.

The system will automatically do this when ESS is setup. The system has all the variables it needs to calculate how much power to export so that grid import/export is 0.

ie It's got grid import/export (from EM24), solar production data (from fronius), and easysolar data. The victron system balances the equation (by outputing from batteries or charging batteries) to get EM24 to show 0 (or whatever number you set grid set point to in ESS settings)

If however you want to make sure batteries have some juice left for critical loads incase you have a power outage you can set the battery limit to a high percentage say 50% and then once state of charge reaches 50% Easysolar will no longer output from battery to ACIN to make EM24 show zero and then if there isnt sufficient solar the grid will need to take over the rest of the load on ACIN side.

The critical loads will then always have 50% of battery to run on incase grid goes down.

This is a crude drawing showing how I ended up setting it up. I did not want to mess with the Fronius part because it went through approval process and it can export to grid. Victron is more for backup power and supplementing the power with the array connected to it and sending it to critical load and normal AC load on phase 1 up to what EM24 shows.

Fronius:

Victron GX discovers Fronius on the network and it can show it but it sees it as an unknown PV inverter even if it shows the Fronius logo on it. I have seen in the docs what needs to be modified in the fronius modbus settings to see it properly but I do not have the Technician password for the Fronius and I am not sure what would be the implication. I am also not sure if I move the EM24 up next to the Fronius Smart meter if I can reliably set the EasySoalr to only feed to the loads and not export to grid but to let Fronius to export to grid.

It sounds like you want fronius system to be the main system and victorn secondary.

I'm not aware of a way of setting it up in the way you've described. If you have the victron as the "main" system you can do as i described above. It would require you meters to be in different places though. ie Fronius meter right next to the fronius inverter and the EM24 where the fronius meter currently is.