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

adorobis · June 18, 2026, 3:14pm

I would start by going straight to the new HACS integration and see if it works. It now has 90% features of my integration and is much easier to set up.

If you have local USB connection just provide which it is and if you are using RS232-network module (e.g. waveshare) configure it with manual/custom port and enter socket://{ip}:{port} providing IP and port of your network module.

bremby · June 18, 2026, 9:30pm

I need help, I cannot make it working with ESP32 + MAX3232 RS232 converter

I cannot make the integration connecting to the remote serial.
how the ESP yaml looks like? how to configure the integration?

samumar · June 19, 2026, 11:46am

Awesome! Any chance to have iti in English?

bremby · June 19, 2026, 5:16pm

I managed to make it work. The issue was the swapped TX/RX lines between the ESP32 and the MAX3232.In case others run into the same problem, a very effective test was to short‑circuit the RX and TX pins on the MAX3232. This allows you to isolate the issue and verify each part of the chain separately: ComfoAir, RS232–TTL converter, and ESP32.

FXB24 · July 3, 2026, 8:15pm

Hi @pepo83, I have now been using your integration quite happily for the last couple of months, no issues, no drama, it just works.
However, during initial setup (screw Terminal at ComfoAir to Waveshare ETH) I had to disconnect the comfosense module wires from the screw terminal since both, the Waveshare and the comfosense module didn't work at all with the comfosense module showing an alarm message with no control ability at all.
Now I was trying to start another initiative to get both running in parallel. Would you mind to share your preferences within the Waveshare module and maybe take a picture of your connection that allows both to work in parallel? Thank you very much!

pepo83 · July 5, 2026, 2:33pm

@FXB24
Hi, you can have a look there:

github.com/pepo83/ha-app-ca350-mqtt-bridge

CA160 with mandatory ComfoSense: HA commands always fail (RS232 mode = 2 permanently held)

opened 06:42PM - 22 Apr 26 UTC

closed 08:32PM - 11 May 26 UTC

Pippo012

## CA160: ComfoSense is mandatory — commands from HA always fail with RS232 mode… = 2 ### Setup - **Unit**: Zehnder ComfoAir 160 (not 350) - **Connection**: Waveshare RS232/485/422 TO POE ETH (B) → RS232 port (DB9) of the CA160 - **Add-on version**: 1.8.2 - **HA OS** on mini PC - **pc_mode tested**: 0, 1, 4 - **comfosense_connected**: True and False both tested ### Problem On the ComfoAir 160, the ComfoSense controller is **not optional** — it is required for the unit to operate. If physically disconnected, the CA160 throws an error and does not start. With ComfoSense connected, the RS232 bus is always controlled by it (RS232 mode = 2). All commands sent from HA fail after 3 retries: ``` [INFO] Sent Fan level 3 (try 1) [INFO] Sent Fan level 3 (try 2) [INFO] Sent Fan level 3 (try 3) [WARNING] Fan level 3 failed after 3 tries [DEBUG] RS232 mode = 2 ``` With pc_mode = 1, the bridge tries to set RS232 mode 1 but it also fails: ``` [INFO] Sent RS232 mode 1 (try 1) [INFO] Sent RS232 mode 1 (try 2) [INFO] Sent RS232 mode 1 (try 3) [WARNING] RS232 mode 1 failed after 3 tries ``` pc_mode = 4 shows no difference in behavior. **Monitoring works perfectly** — all sensors (temperatures, fan %, bypass, summer mode, filter, operating hours) are read correctly in real time. ### Question Is there a way to make the bridge coexist with a **mandatory** ComfoSense on the CA160, so that HA can send commands in the gaps between ComfoSense messages? On the CA160 the ComfoSense appears to hold the RS232 bus permanently. Is there a specific pc_mode or configuration that allows command injection between ComfoSense polling cycles? Thank you for the great work on this add-on — monitoring works beautifully even on the CA160!

FXB24 · July 5, 2026, 3:57pm

Hi @pepo83 ,

actually already tried that one out yesterday, unfortunately without success. As a result of that trial and error process iterating through all possible preference combinations (both Rx to Rx and Rx to Tx). I have now got a situation where setting certain fan levels always results into a verification issue in HA, whilst the actual fan level is set at the ComfoAir module and adapted. Just HA is not acknowleding the change.

04-07-2026 09:18:54 [DEBUG] Invalid escape sequence, resync
04-07-2026 09:18:54 [DEBUG] Frame sync lost, dropping 1 byte

Would you mind to guide me in the right direction on the parallel ComfoSense application and the sudden appearance of what seems to me a miscommunication somewhere in the chain?

Thank you!

pepo83 · July 6, 2026, 10:11pm

The message “Frame sync lost, dropping 1 byte” is normal if it occurs occasionally (this is down to the buffer size of the Waveshare module).
Do you have CC Ease or Comfosense module?
I’m not sure if it actually works without any issues with Comfosense (see the linked thread above); I’m using CC Ease.
What are your settings? Is “Comfosense connected” on or off?
Which commands do you see in the debug log (with RX to TX and Rx to Rx)?
You should see commanda like this:

07-07-2026 00:13:28 [DEBUG] RX 00 3c DATA=88 10 bf 06 06 77 00 00 00 e2
07-07-2026 00:13:29 [DEBUG] RX 00 e0 DATA=00 00 05 64 05 00 01
07-07-2026 00:13:29 [DEBUG] RX 00 e2 DATA=00 00 00 00 00 03
07-07-2026 00:13:29 [DEBUG] RX 00 ec DATA=07 17 17 18 00 00 00
07-07-2026 00:13:29 [DEBUG] RX 00 3c DATA=88 10 bf 06 06 77 00 00 00 e2
07-07-2026 00:13:30 [DEBUG] RX 00 98 DATA=00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
07-07-2026 00:13:30 [DEBUG] RX 00 9c DATA=02

Maybe also try a power cycle on the comfoair unit.

Mumin73 · July 13, 2026, 8:19am

It looks very good. Can you share it?