The Zehnder ComfoConnect PRO is a modular gateway that bridges Zehnder ComfoAir ventilation units (Q350, Q450, Q600, Flex and Classic series) to external building automation systems via Modbus TCP. TapHome connects to the gateway over Ethernet — the gateway then communicates with the ventilation unit over the ComfoNet CAN bus.
The template provides ventilation preset control (Away / Low / Medium / High), four temperature and humidity sensors (extract, exhaust, outdoor, supply), supply airflow reading, filter status monitoring, temperature profile selection and a configurable boost mode.
Hardware connection
The ComfoConnect PRO sits between the home network and the Zehnder ventilation unit. It connects to the ventilation unit via the included ComfoNet cable (CAN bus) and to the network via Ethernet (RJ45) or Wi-Fi.
- Protocol: Modbus TCP
- Port: 502
- Default Slave ID: 1
- Hostname: comfoconnectpro.local (mDNS)
Connector layout
Key connectors relevant for TapHome integration:
| Connector | Function |
|---|---|
| Ethernet (RJ45) | Network connection — Modbus TCP communication with TapHome |
| ComfoNet | CAN bus cable to the ventilation unit (CAN_H, CAN_L, 12V, GND) |
| Modbus RTU (H, L) | RS-485 — alternative for BMS integration (not needed for TapHome) |
| USB | Service connection |
| PSU 12VDC | Power supply input (12V, 2A max) |
ComfoNet cable wiring
| Wire Color | Connection |
|---|---|
| WHITE | CAN_L |
| YELLOW | CAN_H |
| BLACK | GND |
| RED | 12V |
Enabling Modbus TCP communication
Modbus TCP must be enabled through the ComfoConnect PRO web interface before TapHome can communicate with the device.
- Connect the ComfoConnect PRO to your local network via Ethernet or Wi-Fi
- Open a browser and navigate to http://comfoconnectpro.local (or the device IP address)
- Log in with username admin and the password set during first configuration
- Navigate to Configurations > Third Party Settings
- Select Modbus TCP from the protocol dropdown
- Keep the default settings — Slave ID: 1, TCP Port: 502
- Click Apply — the device will reboot to apply the new settings
Saving Modbus TCP settings will reboot the ComfoConnect PRO. The device will be temporarily unavailable during the restart.
Configuration in TapHome
When importing the template in TapHome, provide:
- IP Address — the ComfoConnect PRO’s IP on the local network (check the web interface Network page)
- Slave ID — Modbus slave address (default: 1)
The ComfoConnect PRO supports mDNS — it is discoverable as
comfoconnectpro.local. Assign a static IP address in the router’s DHCP settings to prevent the address from changing after a power cycle.
Device capabilities
The template exposes the following devices:
Ventilation control
- Ventilation (multi-value switch) — ventilation preset via holding register HR:0. Selects the airflow level: Away (minimum), Low, Medium, High. The ventilation unit adjusts fan speeds according to the selected preset.
- Ventilation Boost — toggle switch via coil C:6. Activates maximum airflow for a configurable duration (default 2 hours / 7200 seconds set during template initialization via HR:4). Boost is available when auto mode is disabled.
- Airflow — read-only sensor showing the current supply fan volume flow in m³/h from input register IR:6.
Temperature and humidity monitoring
The template includes four combined temperature and humidity sensors. Temperature values are stored as °C × 10 (Int16, divide by 10), humidity as percentage (Int16, divide by 100).
| Sensor | Temp Register | Humidity Register | Description |
|---|---|---|---|
| Extract | IR:8 | IR:13 | Air taken from rooms before the heat exchanger |
| Exhaust | IR:9 | IR:14 | Air leaving the heat exchanger to outside |
| Outdoor | IR:10 | IR:15 | Fresh air intake |
| Supply | IR:11 | IR:16 | Heated fresh air delivered to rooms |
Room temperature (IR:7) and room humidity (IR:12) are available in the Modbus register map but not included in the template. These require an optional room sensor connected to the ventilation unit.
Temperature profile
- Temperature Profile (multi-value switch) — selects the heat exchanger bypass behavior via holding register HR:1. Values: Normal (balanced), Cold (retains more heat), Warm (allows more bypass cooling).
Filter monitoring
- Filter Dirty — read-only binary sensor from discrete input DI:3. Indicates when the filter needs replacement or cleaning.
- Filter Days Left — read-only sensor from input register IR:25. Shows the remaining filter lifetime in days, counting down from the configured filter lifetime.
Additional register capabilities
The ComfoConnect PRO exposes additional Modbus registers not currently included in the TapHome template:
| Register | Name | Type | Notes |
|---|---|---|---|
| IR:0 | Connection State | Sensor | 0=OK, 30=not CAQ, 40=version incompatible, 50=no unit |
| IR:1–IR:5 | Active Errors 1–5 | Sensor | Error codes (84 defined codes) |
| IR:17–IR:24 | CO2 Zones 1–8 | Sensor | ppm, requires optional CO2 sensors |
| HR:2 | Temperature Profile Mode | Config | 0=Adaptive, 1=Fixed, 2=External Setpoint |
| HR:3 | External Setpoint | Config | °C×10, range 5–35°C |
| C:0 | Reset Errors | Action | Self-resetting coil |
| C:5 | Auto Mode | Config | Enable/disable automatic ventilation |
| C:7 | Away Function | Config | Enable/disable away function |
| C:8 | ComfoCool | Config | Enable/disable passive cooling |
Compatible ventilation units
The ComfoConnect PRO works with the following Zehnder ventilation systems:
- ComfoAir Q series — Q350, Q450, Q600 (ComfoNet compatible)
- ComfoAir Flex — ComfoNet compatible
- ComfoAir Classic series — ComfoAir 160, 180, 200, 225, 350, 450, 550, SL220, SL330, Standard 300, Standard 375 (available from software release 1.1)
Troubleshooting
No Modbus communication
- Verify Modbus TCP is enabled in the web interface (Configurations > Third Party Settings)
- Confirm the ComfoConnect PRO IP address — check http://comfoconnectpro.local or the router’s DHCP lease table
- Ensure TapHome Core and the ComfoConnect PRO are on the same network/subnet
- Check that no firewall is blocking port 502
- Verify the ComfoNet LED is solid green — blinking indicates a cable issue between the gateway and the ventilation unit
Gateway path unavailable error
The Modbus exception code 0x0A (GatewayPathUnavailable) indicates the ComfoConnect PRO cannot reach the ventilation unit over ComfoNet. Check the ComfoNet cable connections and verify the ventilation unit is powered on.
Boost mode not responding
Boost mode via coil C:6 only works when Auto Mode (coil C:5) is disabled. The template initialization script disables Auto Mode automatically, but if it was re-enabled manually, boost commands will be ignored.
