I have a solar inverter (Fronius Symo 15.0-3-M) and a pool heater (AstralPool Heat II). I want the heating to turn on when there is excess power from the solar power station so that the excess electricity don't go back to the grid. So to achieve desired outcome I think I need to find other devices to connect the two together. They are about 200 meters apart so long electric cords are out of the question, but they can both be connected to the same Wi-Fi and/or ethernet at their different locations.
There seems to be a few possible routes here. I am not sure which is the best way to go. Inverter has JSON API. Inverter also has HTTP POST (XML or JSON). Inverter can also send a 12V electric signal. Inverter has ModBus. Heater has ModBus.
Am I looking for a JSON to modbus device of some sort? When JSON hook sent a smart relay turns on the 3phase switch in the electric box powering the heater?
In the future there will probably be more devices using the excess power, this is why I want to set it up smart in the first place.
I have found a world of smart sensors but feel unsure of which kind of devices can perform this task. Most solutions seem like an overkill.
I own a Moxa NPort Express DE-311 which seems capable of receiving a signal and communicating with modbus, would that be a good idea?