Hello everyone
I’ve been using Home Assistant for a few months now and have come across my first major issue.
I have a Zehnder ComfoAir 330, which – as far as I know – uses the same technology as the ComfoAir 350, just in a slimmer design. In theory, it should therefore be possible to integrate it into Home Assistant.
Available hardware:
Wiring setup:
StarTech adapter → DB9 RS232:
- Wire 2 → DB9 pin 3
- Wire 3 → DB9 pin 2
- Wire 8 → DB9 pin 5
RS232 → ESP32 via MAX3232:
- MAX3232 VCC → ESP32 3V3
- MAX3232 GND → ESP32 GND
- MAX3232 TXD → ESP32 GPIO16
- MAX3232 RXD → ESP32 GPIO17
The problem:
When I connected everything, I tried to hook up the StarTech adapter with a custom RJ45 cable directly to the RJ45 port of the ComfoAir. For some reason, this caused a short circuit, most likely because I was working while the unit was powered on and the other wires weren’t isolated. I suspect the 12V line was also involved.
As a result, I ended up damaging the lower board and had to replace both boards to get the ComfoAir running again – an expensive mistake.
My question:
The board has a direct DB9 port. To avoid another short circuit, I’m wondering if it would be possible to connect the MAX3232 directly to the board, which would at least bypass the 12V line.
Do you have any tips or best practices on how to implement this safely, without risking damage to the board again?
Thanks a lot for your support!
Best regards,
Goran