Daikin Altherma 3 air/water heatpump, Daikin Perfera airco connect to HA through Modbus or KNX

Good day!

I’m new at home automation, am a big time open source fan and would love to use Home Assistant in the near future. I’m also at the point for deciding on some big upgrades in my house, getting rid of gas altogether and move to an air/water heatpump and airco units.

I have a nice proposal for getting the following equipment installed from Daikin:

  • 1x Daikin 3MXM68R airco outside unit
  • 2x Daikin FTXM20R airco inside unit
  • 1x Daikin FTXM42R airco inside unit
  • 1x Daikin Altherma 3 heatpump EHVH08S23E9W- LT/ERGA08EV/MADOKA

I read that Daikin offers some cloud hosted service, but I definitely want all the things in my home to run autonomously, so without any external cloud dependencies.

I understood that instead of the WIFI, I can also get either Modbus or KNX connectivity and am wondering if anyone here has experience with either. Specifically for the equipment mentioned above.

I’m not afraid to program a bit myself, but it would be nice if at least the interface exposed from the hardware is somewhat open and accessible :slight_smile:

Which would work best for interfacing with Home Assistant ?
Are all functions (read and write) properly exposed and usable from HA?

Thanks so much!

Hi :wave:!

Unless you have (or are planning to have) an existing Knx installation, I’d go for Modbus. Knx has a big overhead (money-wise) for a single device: power supply + ip interface ~200-350€, ETS license 350-1000€ (Unless you can use Demo forever).

I don’t know the Daikin devices and their differences though.

Hi Farmia, thanks! Ahh, I wasn’t aware that for this KNX I would need some other software, now reading about this ETS - is that some kind of middleware then ? No I don’t have KNX yet, just understood that either KNX or Modbus would be the two ‘open’ options.

So modbus would be good for me too, have long ago done some things with motor control over rs485/modbus. That is at least fully open and free. Thanks.

Then I would need to find out if the Daikin equipment all works with this. The company who offered me the equipment gave an option for modbus interface on the inside airco units, but didn’t specify it for the air/water heatpump, still have an open question to them about it, but they are not too knowledgeable about further integrations it seems.

It’s a (the only) programming/parametisation/commissioning tool for Knx devices. You need it to set up the devices or change their configuration, but then the devices run on their own / decentralized. ETS does not have to be running all the time - so not really middleware.
The demo version handles up to 5 devices and has some minor Limitations that may not affect you for your usecase (eg. no plugin support).

If the Modbus thing uses RTU you might need some TCP gateway, but that shouldn’t be that expensive.

The HA Modbus integration seems a tiny bit more tinkery, but also more flexible than the KNX Integration.

Ah I see, yes, then having a closed commissioning software doesn’t sound great either.

I don’t mind some tinkering at all :slight_smile:

For modbus I found some info here https://www.daikin.eu/content/dam/document-library/catalogues/ctrl/RTD_ECPEN15-308_Catalogues_English.pdf but would need info on which registers are available… Wondering if this RTD-LT/CA would be the right module…

Interesting :slight_smile:

Alright, getting a bit more confident that it may work :slight_smile:

And RTD-RA seems to be suitable for the airco units: http://www.realtime-controls.co.uk/rtd/EN%20RTD-RA%20Installation%20Instructions%2021070-1.07.pdf – i think

Wondering if someone used these with HA before

Seems this is the modbus module necessary for the Altherma 3 LT:

(page also contains tech manuals for modbus registers etc)


I’m planning on buying new Daikin air-condition units (Daikin ftxa-aw - Stylish). My older units in my old house supported the local API and I just learned that support is dropped in newer units and they only support the cloud app.

I’m very happy to learn there’s a way around this with the modbus RTD-RA. However up until an hour ago I never heard of modbus. If my installer installs this modbus on each unit how exactly do I connected it to Home Assitant? I assume I need some hub/gateway where the modbus of each unit is connected to? If that’s correct, which one did you go with?

EDIT: Did some more research and found couple of adaptors to convert RS485 to Ethernet/USB/. Which should work with Modbus - Home Assistant if I understand correctly.

Anyone that can confirm If the products I linked will work with HA?

Currently looking for affordable RS-485 to Ethernet with PoE support…

Did you get this module to work and integrate it with Home Assistant? I also have an Alterma 3LT on order that I want to eventually integrate with HA. Can you recommend a method?