"Connect" modbus devices

[Stieges]

Hey together,

i finally made it and can read values from my modbus devices (thank you Daniel). I thought that if i connect both devices with one object that the value will be written to the other modbus device. In particular i am talking about a PV inverter and a heat pump. I want to send the values of the current DC production and und current DC Export to the heat pump. But somehow it does not work. Unfortunately i didn't find any information in the forum. 
The steps: i read the values of the inverter and write it to an object 12/1/1 and 12/1/2 (write on bus enabled)
I added the heatpump and connected the datafields to 12/1/1 and 12/1/2

Below i send you the Profil for the heatpump.

Code:

{
    "manufacturer": "IDM",
    "description": "Heat Pump",
    "mapping": [
      {
        "name": "Aussentemperatur",
        "bus_datatype": "float32",
        "datatype": "float32",
        "type": "inputregister",
        "address": 1000,
        "units": "°C",
        "value_multiplier":1,
        "writable": true,
        "read_swap": "n"
      },
      {
        "name": "Aktueller PV Überschuss",
        "bus_datatype": "float32",
        "datatype": "float32",
        "type": "register",
        "address": 74,
        "units": "kW",
        "value_multiplier":1,
        "writable": 1,
        "read_swap": "n"
      },
      {
        "name": "Aktuelle PV Produktion",
        "bus_datatype": "float32",
        "datatype": "float32",
        "type": "register",
        "address": 78,
        "units": "kW",
        "value_multiplier":1,
        "writable": 1,
        "read_swap": "n"
      },
      {
        "name": "Aktuelle Leistungsaufnahme",
        "bus_datatype": "float32",
        "datatype": "float32",
        "type": "inputregister",
        "address": 4122,
        "units": "kW",
        "value_multiplier":1,
        "read_swap": "n"
       
      }
     
     
    ]
  }

is the procedure wrong i should have done it with a script? (German manual)
Can somebody help me out with this? i have seen several threads about connection the idm heatpump with iobroker but i didn't see a difference to my parameters.

thx in advance