[APP][Pro] SAJ - HS3 Modbus

Apps
1

I started to work on an app for connecting to your SAJ HS3 (and most likely H2) over Modbus TCP.
It is still an early version but please feel free to test and play around. I will try to improve it quickly based on input.

2

Troubleshooting

Full guide: Homey_SAJ_HS3/TROUBLESHOOTING.md at main · DennisBerggren/Homey_SAJ_HS3 · GitHub

Quick checks if you can’t add the device:

  1. “No answer” / “timed out” – Homey can’t reach the inverter.

    • Check the IP in your router’s client list (the AIO3 module may show up as Espressif). Give it a fixed IP.
    • Make sure Homey and the inverter are on the same network/VLAN.
    • Check that the AIO3 module is online and has decent WiFi signal.
    • Test from a computer on the same network: nc -vz <inverter IP> 502 (Windows: Test-NetConnection <IP> -Port 502). If this times out too, the problem is the network, not the app.

  2. “Refused the connection” – wrong port or wrong device. Port should be 502.

  3. “The inverter closed the Modbus connection” – the AIO3 module only accepts a limited number of Modbus clients. If Home Assistant (SAJ H2 Modbus integration) or another tool is already connected, disable it and try again.

  4. “Did not answer the Modbus request” – check that Modbus unit id is 1.

Control doesn’t work?

  • The app is read-only by default → Device settings → Control → Access → Read and write.
  • If Tibber Smart control is on, Tibber overrides all commands. Control only works with Smart control off. Reading always works.

When reporting a problem, please include: inverter model + firmware, how it’s connected (AIO3 WiFi/LAN), the exact error message, and the result of the nc test.