I recently moved into my new house where we had opted for both a Daikin ducted heat pump and a Daikin ERV. Originally we were going to go with an Airtouch zone control to add to it, but due to the ever rising building costs at the time we had to cut this for other things. However, this meant our only control over the whole system was via the controller on the wall, which was a bit of a step back after using an ESP to previously control wall mounted heat pumps we've had at rentals over the years.

 

So, I started this project which at first seemed pretty simple, I'd just get this AirBase module which already has this Home Assistant integration. This would have worked fine for the Heat Pump, but it has no support for the ERV unit and when I asked Daikin NZ they said I'd end up losing functionality of the ERV even from the wall controller. The rep I was asking from Daikin NZ said they didn't have any controllers that provide remote functionality that are compatible with the ERV, which was a tad frustrating to hear.

 

Upon further investigation, I found that Daikin Europe makes available a range of Modbus controllers from a third party that would allow me to get the same functionality that the Airbase unit was offering in Home Assistant, but also supporting the ERV and all its functions. When I asked the Daikin NZ rep about this they weren't aware of them and weren't able to confirm whether they would be compatible. I emailed the third party company in the UK and they said while they couldn't outright say it would be compatible, since it talks on the same P1/P2 network as any other Daikin controller it should work just fine with an NZ/AU Daikin heat pump and ERV. This convinced me that it was worth a shot so I found an RTD-NET module on eBay for around NZ$200 in Austria, convinced the seller to ship to NZ and waited for it to arrive.

 

Once it arrived, I then had to connect it to the P1/P2 network on the heat pump and then run a cable from the RTD unit in the ceiling back to where I home my Home Assistant box. Thankfully, my partner has worked on heat pumps before and his day job involves electrical work so he "volunteered" to go up into the roof to connect it all up. Everything came back online after it was installed and still functioned while the RTD unit had status lights indicating that it was working and seeing communication on the network. We had passed the first test :)

 

Next was getting it into HA. I have a network based modbus gateway on the way from Aliexpress but in the meantime, I had a USB based one which HA picked up right away. Using this integration guide, I was able to set up a modbus Climate entity that matched to the correct registers outlined in the RTD manual. However, the default modbus integration assumes that the Target Temp and Current Temp use the same scale, however the RTD does not - Target Temp needs to be 1 while Current Temp needs to be 0.01. Thankfully, someone has made a mod for this exact issue which can be installed via HACS. For the ERV control, I decided just to go with switches to set each mode and to toggle between the two ventilation fan speeds. My config as of making this post now looks like this:

 

modbus:
  - name: modbus_hub
    type: serial
    port: /dev/ttyUSB0
    baudrate: 9600
    bytesize: 8
    method: rtu
    parity: N
    stopbits: 1
    climates:
      - name: "Heatpump"
        unique_id: eb2915d4-6231-4a92-b6ae-6ac75b002a98
        slave: 0
        address: 25
        scale: 0.01
        input_type: input
        data_type: int16
        max_temp: 32
        min_temp: 16
        target_temp_register: 1
        target_temp_scale: 1
        temp_step: 1
        temperature_unit: C
        hvac_mode_register:
          address: 3
          values:
            state_heat: 1
            state_cool: 3
            state_auto: 0
            state_dry: 4
            state_fan_only: 2
        # fan_mode_register:
        #   address: 2
        #   values:
        #     state_fan_low: 1
        #     state_fan_medium: 2
        #     state_fan_high: 3
        hvac_onoff_register: 5
    switches:
      - name: "ERV - Auto"
        unique_id: f5802678-2c07-4f19-a42b-4e68a5b6f585
        address: 30
        command_on: 0
        verify:
      - name: "ERV - Recovery"
        unique_id: b30a49a9-2769-4682-ad2c-b010443ef267
        address: 30
        command_on: 1
        verify:
      - name: "ERV - Bypass"
        unique_id: 6418c4ad-ee16-4771-a0b0-46cd9ffede34
        address: 30
        command_on: 2
        verify:
      - name: "ERV - High Fan"
        unique_id: 24204503-0387-409f-b182-5959db78c3d6
        address: 31
        command_on: 2
        command_off: 1
        verify:

 

With everything configured and a reboot of HA, the climate thermostat was available and all controls functioned. As you would expect, any change made via modbus is reflected on the wall controller and vice versa. With a quick addition to my HomeKit config in HA, it's now also available for Siri to control as well. I setup a simple dashboard in HA for full control as well:

 

 

Overall, it was an interesting project to undertake and pretty satisfying to get working. Even better, it's all local so all control is instant and I don't have to worry about a service being offline to control it from my phone. I figured it was worth documenting this here so others here in NZ or even Aus that want to do something similar have something to go off. Next step will be to change the config to work with the network gateway on the way.