Supports home assistant 2023.05 or newer

Zehnder comfospot twin 40

To read/write on the bus, use this waveshare adapter. Find it on the waveshare website Others don't seem to function properly

Setup:

• Buy the waveshare adapter
• Setup you MQTT server
• In case you want to use home assistant, ensure you run 2023.05 or newer.
• Set the internal jumper to NC.
• Set the voltage to 5V
• Only A+ and B- need to be connected. GND is not connected.
• Disconnect the original touchscreen, as the protocol only supports one master on the bus.
• After cloning this repo, run pip install -r requirements.txt

To only read from the bus, a cheap RS485 reader is sufficient.

python server.py --help
usage: server.py [-h] --mqtt MQTT [--mqtt-port MQTT_PORT] [--mqtt-prefix MQTT_PREFIX] [--dev DEV] [--oscillation OSCILLATION] [--sensorvalidity SENSORVALIDITY] [--state STATE] [--reverse]

options:
  -h, --help            show this help message and exit
  --mqtt MQTT           MQTT address
  --mqtt-port MQTT_PORT
                        MQTT port
  --mqtt-prefix MQTT_PREFIX
                        MQTT prefix
  --dev DEV             Serial device
  --oscillation OSCILLATION
                        Oscillation time in seconds
  --sensorvalidity SENSORVALIDITY
                        Sensor data validity in seconds
  --state STATE         JSON file to store state
  --reverse             Fans are installed reversed

About the comfospot

This seems to be a OEM product by GetAir sold under the Zehnder brand. It's available under these brand names:

• Zehnder ComfoSpot Twin 40
• Zewotherm Fan
• GetAir SmartFan
• Kermi x-well D12 (in case you don't get a signal, try switching the A and B wires)
• Viessmann Vitovent 100-D

Only the Zehnder has been tested, but devices from other manufacturers should work as they seem identical.

Temperature & humidity sensor.

The sensor is a Sensiron SHT21 i2c based sensor.

Packet specification

Packet header

• 00 0x55 Preamble
• 01 0x4D Preamble
• 02 0x00 Preamble
• 03 0x96 Preamble
• 04 Data length excluding checksum

Fan level

The maximum fan level is 100 Setting a fan level of 101 or higher will stop the fan The minimum fan level seems to be 26 0x1a

Zones

There are 3 user zones (DIP switch 1 to 3 on the fans). If none of the DIP 1 to 3 switches is set, the fan joins the first group.

On protocol level there are 6. In fact the [protocol level] == [user zone - 1] * 2 These are the even zones (DIP switch 4 set to OFF on the fans).

If DIP switch 4 on the fan is set to ON. The fan will listen to the odd zones.