I can access the relays on the GX ( although it’s after wading through a lot of menus on the “ remote “ menu but I can’t work out how to turn on and off the relay on the inverter.
Any advice on how I can turn the inverter relay on and off ( remotely )
If you have access to the dbus path of that relay and changing the value there the relay turns on and off, then the Modbus address is not a problem.
You can either:
You can manually add / allocate an address for that path on the Modbus config in order to use Modbus.
Create the entry on the Remote Console to control that dbus path.
But both of these need for you to have some programming skills…
Many devices have an entry on their menu to show the relay state. But it’s readonly.
Easiest, if you have that option is to just enable it by modifying the qml file responsible.
Here is how it looks on my Multi RS. (It’s enabled on my system)