Hello openHAB Community!
I’m excited to share an open-source hardware project i am working on to bridge the gap between traditional radiators and modern low-temperature heating systems. The Smart Heating Fan Controller is intended for optimizing radiator efficiency through intelligent forced convection, see also Figure 1.
Why Forced Convection?
- Efficiency: Increases heat output by 30-50% at the same flow temperature.
- Heat Pump Ready: Allows flow temperatures to drop by 10-15°C, significantly increasing Heat Pump COP.
- Comfort: Faster room warm-up and better heat distribution
I am proposing the development of a openHAB binding to bring it into our ecosystem and asking for support in advancing the PCB, as my resources are unfortunately limited.
That is why, I am making all hardware designs, PCB files, and 3D models open source:
- PCB: GitHub: Heating-#Fan-Controller (All KiCad & PCB files)
- 3D Printable Housing: Thingiverse - PCB Enclosure
- 3D Printable Fan Clips: Thingiverse - Radiator Fan Clips
While I have the hardware and basic MQTT integration running, I’m looking for community experts to help evolve this into a polished openHAB solution. Furthermore, I see the hardware as a foundation that could eventually evolve to include direct valve control, creating a full radiator management system.
Figure 1: Illustration of the Smart Heating Fan Controller System
What is this System?
The system is based on ESP32-S3 board that manages fans mounted beneath radiators, see Figure 2. By monitoring four distinct temperature points, it enables the implementation of sophisticated control strategies to increase heat transfer.
Figure 2: PCB with ESP , temperature sensor connectors (S1-S4) and 4Pin fan connectors (F1-F2)
Key Hardware Features:
- MCU: ESP32-S3 (WiFi/Bluetooth).
- Sensors: 4× DS18B20 inputs (S1 - Flow, S2 - Flow Return, S3 - Air Inlet, S4 - Air Outlet)
- Outputs: 6x synchronized fan channels (F1 to F6) with a common PWM signal.
- Power supply: via 12V DC connector (DC0)
- Tactile Buttons:For manual interaction ( SW1 - SW3, e.g. Fan speed ±, Fan On/OFF)
- Firmware (option): Tasmota configuration for easy MQTT integration is available.
- GPIOs: All unused GPIOs accessible via PIN Headers
Recommended Fans: High-quality PC fans operating at low speeds (<500 RPM) are essentially inaudible while providing significant heat output improvement. The controller supports both 3-pin and 4-pin fans.
Performance Analysis & Data:
The chart in Figure 3 shows real system behavior over a 24-hour period using a standard ON/OFF fan logic. The data was recorded using the fan installation shown in Figure 4. The smart heating fan controller is not depicted as it is mounted on the back side of the heating.
Figure 3: System performance chart
The performance chart in figure 3 shows:
- Temperature Deltas: The chart tracks the critical relationship between the water flow/return (VL/RL) and the air inlet/outlet. You can clearly see the “Temperaturdelta Luft” (Yellow line) spikes when the fans are active, indicating successful heat extraction.
- System Latency: The “On/Off” green blocks show the current binary logic. There is a clear opportunity here for PID control: instead of these hard pulses, a dedicated binding could modulate fan speed to maintain a constant, optimal air delta.
- Efficiency Correlation: Note how the “Temperaturdelta HK” (Blue line) reacts to fan activity. This real-world data proves that we can extract significantly more energy from the water loop than natural convection alone allows.
Figure 4: 4x 120mm PC fan installation with flow and return flow temperature sensors straped to the pipage
Vision: Integrated Control Strategy
Current Implementation: Tasmota handles I/O and publishes MQTT data. OpenHAB switches the fans ON and OFF based on a fixed temperature threshold using a constant fan speed.
Target openHAB Binding:
-
Auto-discovery of controllers
-
PID/Adaptive control based on water and air temperature deltas
-
Real-time efficiency monitoring
Future Development: Add 3.3V motoric driver (e.g., MP6550) to control valve actuators like Homematic IP, enabling complete radiator management
Call for Collaboration
I’m seeking help to advance this project:
-
Binding Developers: Create a polished openHAB binding or MQTT template
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Hardware/Firmware Contributors: Design and test valve actuator integration and improved cable management
Happy to discuss technical details on PCB design, Tasmota templates, or thermal dynamics. Looking forward to your feedback!
Best regards,
P.S.: I am considering to order a batch of new PCBs. If you’re interested, please contact me via PM!