ESPHome Modbus Brink Flair 400 controlling questions

ESPHome
1

Hi All,

I made a script to read the status of a Brink Flair 400 (Heat recovery appliance house ventilation) by modbus (RS485). It works great. See: ESPHome RS485 Brink Flair WTW no entities shown - ESPHome - Home Assistant Community (home-assistant.io)

Now I would like to controll it, also. I made this script:

number:
  - platform: modbus_controller
    modbus_controller_id: brink
    name: "Ventilatie stand"
    id: ventilatie_stand
    address: 8001
    value_type: S_WORD      
    min_value: 0
    max_value: 3
    mode: slider

I got an error when I change the slider:

Modbus error function code: 0x6 exception: 3
Modbus error - last command: function code=0x6 register adddress = 0x1F41 registers count=1 payload size=2

I tried to ad: register_type: holding but using holding is not allowed.
What am I doing wrong?