Modbus: Writing values / Climate control with value conversion

[tomvoo (Tom)]

Hi there,

I’m trying to control my water heat-pump and the temperature values require some conversion to become celcius. Like so:

Celcius = (value - 30) / 2

It looks like it’s Fahrenheit but it’s actually not so I cannot use the built-in C → F / F → C conversion.

For reading the registers i’ve already made a template function like so:\

- sensor:
  - name: water_heatpump_current_temperature_celcius
    state: "{{ (((states('sensor.water_heatpump_current_temperature') | int)-30) / 2)|round(0) }}"
    unit_of_measurement: "°C"
    device_class: temperature
    state_class: measurement
  - name: water_heatpump_target_temperature_celcius
    state: "{{ (((states('sensor.water_heatpump_target_temperature') | int)-30) / 2)|round(0) }}"
    unit_of_measurement: "°C"
    device_class: temperature
    state_class: measurement

I prefer to use a climates sensor to achieve this because of the UI but if that doesn’t work i’d like to know how to just go about writing converted values.

Thanks

[tom_l]

@tomvoo

For reading the registers i’ve already made a template function like so:\

You did not need to do that. The modbus sensor supports options you can use in the sensor definition to do the conversion.

So in your case just add this to your modbus sensor:

offset: -15
scale: 0.5

For writing, say you want to send the value 30

action:
  - service: modbus.write_register
    data_template:
      address: # supply this
      unit: # supply this
      hub: # supply this
      value: >
        {% set value = 30 %}
        {{ (2 * value + 30)|round(0)|int(0) }}

If you wanted to send the value of an input number or sensor:

      value: >
        {% set value = states('input_number.foobar')|float(0) %}
        {{ (2 * value + 30)|round(0)|int(0) }}

      value: >
        {% set value = states('sensor.foobar')|float(0) %}
        {{ (2 * value + 30)|round(0)|int(0) }}

[tomvoo (Tom)]

@tom_l Thanks Tom! I missed those inline conversions! Would this also work for the climates component?

[tom_l]

It has the same options: Modbus - Home Assistant It appears to be a global setting for the climate entity though.

[tomvoo (Tom)]

@tom_l Thanks again, i got it working!

[tomvoo (Tom)]

hey @tom_l sorry to hijack this again, but you might have an idea on this. After I added the climate component which reads the current temperature from address 113 it seems the original sensor current_temperature is showing as Unavailable.

sensors:
    - name: water_heatpump_current_temperature
      unique_id: f8c8a1a9-ef93-4764-a744-2aeeaa4ee2ca
      scan_interval: 30
      address: 113
      slave: 1
      offset: -15
      scale: 0.5
climates:
    - name: "water_heatpump_climate"
      address: 113
      slave: 1
      input_type: holding
      max_temp: 70
      min_temp: 30
      precision: 1
      target_temp_register: 2
      temp_step: 1
      temperature_unit: C
      hvac_onoff_register: 0
      write_registers: true
      offset: -15
      scale: 0.5

Any idea?

[tom_l]

Unfortunately no I don’t. I don’t actually use the modbus integration. Perhaps trying to read the same register is causing some sort of conflict?

As an alternative you could create a template sensor from the climate device if you need the current temperature attribute somewhere that does not support attributes directly.

[tomvoo (Tom)]

Thanks for the hint, using an entity attribute works fine! I didnt know those existed

[Evgenius]

Where should I put this?

In this menu?

[tomvoo (Tom)]

It’s an action. look for the service under actions, not triggers

[Evgenius]

I found where to add actions! Developers, couldn’t you put the actions tab somewhere else? It would be more logical to place the actions tab next to the “Trigger” tab!

[CHW1979 (Christoph Wijns)]

Hello,

I’m so confused (noob) but where do you set those entries please ?

I have a stiebel eltron heatpump and I can read data - no problem - but I like to set temperature and I don’t know how to begin.

Please help

Christoph

[tomvoo (Tom)]

Hey Christoph, writing is the same as reading in the sense that instead of checking what value is stored in a register you just write to a register. Which register you have to find out using the manual for the Stiebel unit.