Zehnder ComfoAir CA350 integration via serial connection (RS232) and MQTT

[nldav]

@st1jn

However i am not sure about the pin out i tried a couple of combinations but nothing seems to work. Has anyone got any ideas. tips or resources to set me in the right direction?

please use a multimeter to measure +12V to ground
measure the ground pin as well by measuring resistance (to chassis, or some other clear ground point)
the other two is RX and TX, if you mix those up it doesnt do damage

do not randomly try something as you might fry either the external board or the mainboard when trying this 12V output on the wrong pins of the ESP8266.

this is the pin layout of the RJ45, I expect the same sort of layout for your type of connector but measuring first doesn’t hurt.

[920er]

I am new to this topic and still diving into this to build up basic knowledge.

Our house has a Zehnder Comfoair 550 Luxe from 2012, with CC Ease connected with cables.

(RS232 and RJ45 also available but not in use.)
I plan to disconnect the CC ease and connect a PI (preferably the Zero W I have lying around) with a USB TTL Adapter to the cable terminals, so I wouldn’t need to use the RS232 or RJ45 socket adapters.

The wiki does not list USB TTL Adapters that have been tested to work. I have an old USB TTL labelled “MW 597” with CH340G chip, this shop mentions FTDI in its description:
https://eckstein-shop.de/QITAUSB20TTLKonverterAdapterCH340GUARTFTDIArduino?googlede=1&srsltid=AfmBOorgdGgFuUYK1qekxwqyBuMB5w6a2ddFOr1M0AgarGt3ASyR0x3OlIo
would this be worth a try?

Does the adapter need a separate 5V power input or will it be powered by USB from the PI?

I have another one with CPE2102 chip
https://eckstein-shop.de/32C3V2F5VTypAUSBtoTTLKonverterUART5PinSerialSTCChipCP2102ModuleArduino

In case both of these adapters are not suitable, can you recommend a USB TTL one, possibly powered by USB or with 12V from the Comfoair terminal?

[adorobis]

I’m sorry but I can’t recommend any adapter as I was using RS232 PCI-E card in my NAS. According to my knowledge TTL is not the type you are looking for, you need the RS232 protocol type. You can read a bit here:

RS232 vs TTL: Beginner Guide to Serial Communication - Latest News from Seeed...

Warning: the most notable difference is the voltage. Comfoair operates at 12V:

The minimum and maximum voltages of RS-232 signals are +/-13V, while TTL signals are 0 to 3.3V/5V.

Anyway based on my experience I would go for a RS232 - Ethernet (or Wifi) adapter and deploy the python script in Docker. Depending on a selected adapter you can also power it from 12V in the comfoair directly so no additional power adapters or cables would be required. Some of those devices are also quite small so you could even try to fit them inside the comfoair box.
This Docker Wiki is listing a few devices which have been successfully tested. I’m using the wifi one since a few months and it is super reliable.

[920er]

Ok, so I forget about TTL and we have proof that I am a complete novice in this matter.

So the RS232 converter reads and writes data from the RS232 interface and provides it via an IP entity to the local network? And the PI uses python to provide it to MQTT for HA?

The reason I am asking is that I understood from this explanation that the RS232 is directly connected to the PI via USB, no WiFi or Ethernet, only the PI exposed the Mqtt to the LAN.

I run HAOS on a Futro S920 thin client, which has a RS232 port. Is there a way I can simply connect the comfoair to this port and make use of it directly? I have no docker or proxmox experience or possibility.

I also run Pi hole on a dedicated PI 3, can I use this for the python functionality on top of Pi hole?

Or would a separate, dedicated PI be necessary for the python part?

[adorobis]

@920er

The reason I am asking is that I understood from this explanation that the RS232 is directly connected to the PI via USB, no WiFi or Ethernet, only the PI exposed the Mqtt to the LAN.

Yes, that’s correct. But you don’t need a dedicated RPi for that. If you have rs232 on you HA RPi and it is nearby your comfoair unit you can deploy the python script on HAOS directly. There is a dedicated wiki for that option:

Home Assistant Operating System

I’m just not an expert in HAOS as I don’t use it - that wiki was prepared by someone else - source of this wiki is in the following discussion.

[920er]

Thank you!
The pals in that discussion seem to use an PI 4 or an X86 with a USB adapter. My S920 with built in RS232 on HAOS x86-64 is a slightly different scenario. I can only hope that the RS232 data is somehow exposed to the HAOS so the script can access it. Will give it a try, have to find a suitable cable first. So far I haven’t used the command line in the thin client since I installed HAOS, only GUI configurations.

[920er]

Another question.

When connecting the Comfoair directly to the RS232 port of my HAOS x86-64 Thin client Futro S920, which cables/pins do I have to connect:TX/RX, GND, and not 12V as this would only be needed to power the CC Ease or a RS232 to USB converter? This would mean that I cannot simply buy a RS232 cable with two DB9 plugs for the connection, but have to get rid of the 12V pin in order no to fry my thin client’s RS232 port?

Would try to use a DB9 on my thin client and the green terminals on the Comfoair, but still I need to know which pins to use.

[adorobis]

Pinout is explained at the beginning of this post:

Zehnder ComfoAir CA350 integration via serial connection (RS232) and MQTT

You need a RS232-USB TTL adapter, ideally with FTDI chip for example something like that: https://allegro.pl/oferta/adapter-konwerter-usb-do-rs232-com-ftdi-db9-1-5m-7708396188 On the comfoair side you can use either the RJ45 plug, you need to connect cables like that: [image] rj45 pin 2 -> rs232 pin 3 - yellow rj45 pin 3 -> rs232 pin 2 - white rj45 pin 8 -> rs232 pin 5 - green [image] You can also plug the RS232 plug to the socket in the comfoair - mine has it and I use it this way. You…

[920er]

Thank you, I see the pinout. My question is: Are RX, TX and GND sufficient for the data connection to the thin client’s RS232 port? I don’t think I should connect the 12V from the Comfoair to the thin client as well, this is probably only needed to power the CC ease and can do harm to my thin client’s RS232 port.

[adorobis]

No, you just need Rx, tx and ground.

[mondychan]

how did you get it running? i have the same problem as you did, its empty, nothing shows up in the card,
i verified all the entities by hand and they are set properly

type: custom:mqttcomfoair-card
climateEntity: climate.ca300_climate
outsideTempSensor: sensor.ca300_outside_temperature
exhaustTempSensor: sensor.ca300_exhaust_temperature
returnTempSensor: sensor.ca300_return_temperature
supplyTempSensor: sensor.ca300_supply_temperature
filterStatusSensor: binary_sensor.ca300_filter_status
bypassValveSensor: binary_sensor.ca300_bypass_valve
summerModeSensor: binary_sensor.ca300_summer_mode
returnAirLevelSensor: sensor.ca300_return_air_level
supplyAirLevelSensor: sensor.ca300_supply_air_level
preheatingStatusSensor: binary_sensor.ca300_preheating_status

[adorobis]

Are you sure which card are you using? The one shown by @pusher is not the one you’ve configured in the type: section.

[mondychan]

ah, interesting, i believed we both used the same TimWeyand/lovelace-comfoair, thx tho
in the meantime I was able to get it working with this config for anyone looking for one

type: custom:mqttcomfoair-card
entity: climate.ca300_climate
tempSensor1: sensor.ca300_outside_temperature
tempSensor2: sensor.ca300_exhaust_temperature
tempSensor3: sensor.ca300_return_temperature
tempSensor4: sensor.ca300_supply_temperature
filterstatus: binary_sensor.ca300_filter_status
bypass_valve: binary_sensor.ca300_bypass_valve
summer_mode: binary_sensor.ca300_summer_mode
fan_speed_supply: sensor.ca300_supply_fan_speed
fan_speed_exhaust: sensor.ca300_exhaust_fan_speed
return_air_level: sensor.ca300_return_air_level
supply_air_level: sensor.ca300_supply_air_level

having same issue as @pusher had, no “controls” for fans, but that is not a huge problem for me, i mostly want it for monitoring anyways

[920er]

I read through this thread during the last days, now changed my plan from using my thin client’s internal RS232 to following Dapolux guide, using a dedicated PI Zero W (which I already have) with a USB/RS232 adapter (already ordered, should arrive in the next days), plus Micro USB to USB OTG Adapter for connecting USB/RS232 to the Zero.

Dapolux guide is from January 2021… is it still up to date?

I would use Pi OS lite (latest bookworm version, 32 bit) on my Zero W, headless setup, then work through the guide… or do I have to change anything due to changes in the scripts after 2021?

[naytsyrhc]

Hi there,
so I’m trying to get my Zehnder comfoair 350 luxe into HA.

I bought a device recommended in this thread/linked project (Waveshare RS232/485 TO Wifi ETH) and connected it to the device via the RS232 port of the system.

As mentioned in the thread above, I also disconnected the control unit previously connected to the board via RS232.

Unfortunately, I am currently failing to follow the instructions for the Waveshare device and how to set it up. I can connect it to my network via wifi, but I can’t get it connected via Ethernet. I also can’t connect to the device with the Docker container.

I guess I haven’t quite figured out how the device works. My naive thought was that I can simply connect the device to the Zehnder, integrate it into the network and then get a server accessible via TCP, which is then queried by the Docker container and transmits the results to Homeassistant via Mosquitto Broker.

All the examples above seem to use some devices translating the signals to USB and connected to HA directly or a raspberry Pi.

I thought the Waveshare device to be able to act on it’s own?
I want to avoid an extra raspberry pi and my HA server is too far away from zehnder to connect it.

[adorobis]

@naytsyrhc

Unfortunately, I am currently failing to follow the instructions for the Waveshare device and how to set it up. I can connect it to my network via wifi, but I can’t get it connected via Ethernet. I also can’t connect to the device with the Docker container.

Which instructions are you following? Have a look here:

Docker container

For the ethernet connection. If you can connect it to wifi, go to the web page of the device (its IP address) and you can configure the connectivity there. It might be that you have to enable the ethernet port first. I have it disabled but I don’t remember if it was disabled by default:

[naytsyrhc]

I ment the instructions for the waveshare device, as I am not able to get it connected to ethernet. I tried what you suggested (enable ethernet) but it doesn’t get an IP assigned by my DHCP. I can’t find how to set static IP for ethernet.

But even without that, following the instructions of the docker container, if connectes to Wifi, I can’t connect to any service of the waveshare device. Open ports are only 23, 80 and 8000. So I presume, some service on waveshare device it not yet enabled?

[adorobis]

So how do you configure the wifi connection of the waveshare device? Does it connect to the wifi and does it respond to ping?
If it connects to the network open its web page (device’s ip address) in a browser:

There is a page to enable ethernet port:

and another page to configure the UART service (below my settings that work well with comfoair):

and next page with network settings (again, below works for me). Ignore the IP address as it is grayed out and not relevant anyway:

Regarding the static IP, there is only one place to set it up and I’m not sure if it will apply to ethernet connection as well. Worst case you can just set static lease on your router.
Below works for me but I’m using wifi only.

It is quite hard to try to help you if you are not posting any configuration from docker or screenshots from your device config. I’ll stop here unless you share what exactly you have configured so far.

[naytsyrhc]

You’re right, it’s not easy to help, if no config is shown. But I was so completely lost with the waveshare device, that I thought it wouldn’t help to show screenshots of the “default” configs.
Your screenshots helped and I resetted the device and configured it accordingly (I omitted the ethernet setup for now, to see, if I can get it to work on Wifi).

So, what I did is almost a copy of what you showed me (can’t add all screenshots, as a new user I’m only allowed to embed one, which follows).

After rebooting I saw a new port open on waveshare device:

I configured the docker-container:

version: '2'

services:
  hassioaddon-comfoair350:
    image: k42sde/hassioaddon-comfoair350:latest
    container_name: hassioaddon-comfoair350
    environment:
      - SOCAT=True
      - COMFOAIR_IP=192.168.66.250
      - COMFOAIR_PORT=8899
        #      - SERIAL_PORT="/dev/comfoair350"
      - RS485_PROTOCOL=False
      - REFRESH_INTERVAL=10
      - ENABLE_PC_MODE=False
      - DEBUG=True
      - MQTT_SERVER=192.168.66.249
      - MQTT_PORT=1883
      - MQTT_KEEPALIVE=45
      - MQTT_USER=False
      - MQTT_PASSWORD=False
      - HA_ENABLE_AUTO_DISCOVERY_SENSORS=True
      - HA_ENABLE_AUTO_DISCOVERY_CLIMATE=True
      - HA_AUTO_DISCOVERY_DEVICE_ID=ca350
      - HA_AUTO_DISCOVERY_DEVICE_NAME=CA350
      - HA_AUTO_DISCOVERY_DEVICE_MANUFACTURER=Zehnder
      - HA_AUTO_DISCOVERY_DEVICE_MODEL=Comfoair 350
    restart: always

And started it. Unfortunately, it still doesn’t connect to the Waveshare device:

hassioaddon-comfoair350    | create serial device over ethernet with socat for ip 192.168.66.250:8899
hassioaddon-comfoair350    | 2025/08/08 12:47:34 socat[9] N PTY is /dev/pts/0
hassioaddon-comfoair350    | 2025/08/08 12:47:34 socat[9] N opening connection to AF=2 192.168.66.250:8899
hassioaddon-comfoair350    | 2025/08/08 12:49:49 socat[9] E connect(7, AF=2 192.168.66.250:8899, 16): Connection timed out
hassioaddon-comfoair350    | 2025/08/08 12:49:49 socat[9] N exit(1)
hassioaddon-comfoair350    | create serial device over ethernet with socat for ip 192.168.66.250:8899
hassioaddon-comfoair350    | 2025/08/08 12:49:50 socat[9] N PTY is /dev/pts/0
hassioaddon-comfoair350    | 2025/08/08 12:49:50 socat[9] N opening connection to AF=2 192.168.66.250:8899

The port is open however:

> telnet 192.168.66.250 8899
Trying 192.168.66.250...
Connected to 192.168.66.250.
Escape character is '^]'.

There seems to be something missing still?

Edit: .249 is the IP of my homeassistant, .250 the one for the waveshare device it obtained from my DHCP server on connecting to my WiFi.

[adorobis]

I’m personally using adorobis/hacomfoairmqtt:latest image as it contains the latest version of python script (and works very well for me).

Looks like it times out when trying to open the connection. So to troubleshoot: can you try to run a docker container in an interactive mode and see if you can create the virtual serial port from command line?
You can do the following commands from your host command line:

docker run -it bitnami/minideb bash
apt update
apt install -y socat
/usr/bin/socat -d -d pty,link="/dev/ca350",raw,group-late=dialout,mode=660 tcp:"192.168.66.250":"8899" &

and as a result you should see something like:

root@0ba0bef89ed9:/# 2025/08/08 14:18:39 socat[417] N PTY is /dev/pts/1
2025/08/08 14:18:39 socat[417] N opening connection to AF=2 10.144.30.104:8899
2025/08/08 14:18:39 socat[417] N successfully connected from local address AF=2 172.17.0.2:51262
2025/08/08 14:18:39 socat[417] N starting data transfer loop with FDs [5,5] and [7,7]

If you’ll still get a timeout/exit instead I would investigate your docker setup.