Hi everyone,
I’m developing an open-source Home Assistant integration for PROXON ventilation and heating systems that communicate over HESP.
My own system is a PROXON P2 without a Modbus module. I wanted to bring its existing operating data into Home Assistant, so I started working on an integration that listens to the communication already taking place inside the system.
The project is available here:
PROXON HESP for Home Assistant
English overview
This is an independent community project, with no manufacturer affiliation.
My hardware and connection
My reference system has:
- A Hermes LT-ZIM V1.6 main board.
- A PTC 4× V1.2 board.
- A BDE Comfort control panel showing V03.6.07A0.
- A transparent RS485-to-TCP gateway, configured for 19200 baud, 8N1.
On this particular board combination, the connection I monitor is between PTC-X2 and main-board X5. This is a different bus section from the direct connection between the BDE and the PTC board.
The connection looks like this:
Existing PROXON HESP bus
│
Transparent RS485-to-TCP gateway
│
Local network
│
Home Assistant + PROXON HESP integration
The gateway forwards the serial data unchanged. Modbus TCP/RTU conversion must not be enabled. No MQTT broker or separate decoding application is required.
These connector names describe my installation, not a universal wiring guide. Board revisions and pin assignments need to be checked for each system, and electrical installation work should be handled by someone qualified.
What currently works
The integration can expose supported values such as:
- System temperatures and room/target temperature.
- Requested fan level and the controller’s reported fan level.
- Supply/extract fan speeds and compressor speed.
- Compressor-running indication, bypass status and intensive ventilation.
- Operating-hour counters and remaining filter runtime.
- Diagnostic information and passive recordings for further analysis.
The beta also includes optional room monitoring using existing Home Assistant switches, power sensors and temperature sensors. It is not tied to a particular device manufacturer and does not take over the room thermostats.
The focus is monitoring. Normal operation and diagnostic recordings do not send queries or control commands. The beta has one explicit exception: an optional, manually triggered device-clock synchronization.
General fan/heating control is not available. A running compressor also does not yet give me a reliably confirmed distinction between heating, cooling and defrosting.
How to install it
For a compatible, correctly connected system:
- Configure the gateway as a transparent TCP server with the serial settings above.
- Add the repository to HACS as a custom repository of type Integration.
- Download the integration and restart Home Assistant.
- Add PROXON HESP under Settings → Devices & services, then enter the gateway address, TCP port and hardware profile.
The project currently requires Home Assistant 2026.9 or newer. Please check the compatibility documentation and release notes before installing. Other PROXON models or board revisions are not automatically supported.
This project does not currently cover the T300 hot-water unit or replace the separate PROXON Modbus approach discussed here.
Where help would make a difference
I would appreciate help from other owners, developers and anyone familiar with these controllers.
1. Compatibility reports from other installations
Which PROXON model, board revisions and BDE software version do you have? If you already have a suitable connection, which values work and which differ from the display?
A short report is useful even without a recording. Please include the bus connection point, gateway settings and integration version.
2. Diagnostic recordings with a known reference
Recordings from other installations could help distinguish common protocol behaviour from installation-specific settings.
The most useful recording comes with a short description of what the BDE showed and when. For example:
- A manually selected fan level.
- Intensive ventilation being enabled and disabled.
- A normal compressor start or stop.
- Naturally occurring defrosting, confirmed by the BDE.
A photo and timestamp can be enough for a stable state; a short video can help with transitions. Please include the timezone. There is no need to force defrosting or repeatedly switch between heating and cooling.
For supported installations, the integration can record through its existing connection. Start a recording on the device page, note the BDE state or action, then stop it and download the Home Assistant diagnostics. The default two-minute recording is a reasonable starting point for a simple comparison. Automatic event recordings are also available.
Please review diagnostic files before sharing them. The integration omits configured network addresses and identifiers, but Home Assistant metadata and raw bus data can still contain installation-specific information. Please do not post credentials, serial numbers or private documents.
3. Fan settings and their meaning
On my installation, manually checking all four fan levels gave these raw control values for both fans:
| Fan level | Raw control value |
|---|---|
| 1 | 2500 |
| 2 | 4000 |
| 3 | 5200 |
| 4 | 10000 |
Another contributor’s installation uses different values. This is why I do not want to hard-code a universal conversion.
If your BDE exposes the configured values for each supply/extract fan level, a photo including the labels and units would be particularly useful. Please leave those settings unchanged. If the menu is unavailable, there is no need to access a protected service menu.
4. Protocol knowledge and development
Documentation or confirmed explanations of HESP data points, status bits, device identification and control behaviour would be very welcome. Code reviews and tests against recorded data would also help.
The protocol work builds on Markus Mauch’s HESP documentation, and contributions from other owners have already helped substantially.
My aim is to make the integration useful across compatible installations while keeping confirmed values clearly separate from experimental interpretations.
If you have a similar system, I’d be interested to hear about your hardware and what you would like to see in Home Assistant.
Thanks!
David