Hello,
I managed to get it working with lots of trial and error and the climates integration, here’s my configuration.yaml
I hope it helps someone 
modbus:
- name: modbus_serial
type: serial
baudrate: 9600
bytesize: 8
method: rtu
parity: N
port: /dev/ttyUSB0
stopbits: 1
sensors:
- name: "wp_outlet_temp"
scan_interval: 10
address: 3
slave: 1
input_type: input
scale: 0.1
device_class: temperature
unit_of_measurement: '°C'
- name: "flow_rate"
scan_interval: 10
address: 8
slave: 1
input_type: input
scale: 0.1
unit_of_measurement: 'l/min'
- name: "outside_temp"
scan_interval: 10
address: 12
slave: 1
input_type: input
scale: 0.1
device_class: temperature
unit_of_measurement: '°C'
switches:
- name: "Heizung"
slave: 1
address: 0
write_type: coil
command_on: 1
command_off: 0
verify:
input_type: coil
address: 0
state_on: 1
state_off: 0
- name: "Warmwasser"
slave: 1
address: 1
write_type: coil
command_on: 1
command_off: 0
verify:
input_type: coil
address: 1
state_on: 1
state_off: 0
- name: "Silent Modus"
slave: 1
address: 2
write_type: coil
command_on: 1
command_off: 0
verify:
input_type: coil
address: 2
state_on: 1
state_off: 0
climates:
- name: "lg_therma_heizung"
address: 3
slave: 1
input_type: input
count: 1
#data_type: custom
max_temp: 45
min_temp: 15
offset: 0
precision: 0
scale: 0.1
#structure: ">f"
target_temp_register: 2
temp_step: 1
temperature_unit: C
hvac_mode_register:
address: 0
values:
state_cool: 0
state_heat: 4
- name: "lg_therma_warmwasser"
address: 5
slave: 1
input_type: input
count: 1
#data_type: custom
max_temp: 57
min_temp: 40
offset: 0
precision: 0
scale: 0.1
#structure: ">f"
target_temp_register: 8
temp_step: 1
temperature_unit: C
The only bug that’s still unresolved is this behaviour:
For now it’s low priority for me since it doesn’t affect the functionality, but eventually I would like to fix it. Unfortunately I don’t see a way to add a dummy sensor for that, because the climate integration directly accesses the modbus registers, and there’s no obvious way to use a “normal” sensor instead.