Hargassner Heizkesselsteuerung
Integrates Hargassner boiler control via Modbus TCP
This ModbusCloud template integrates Hargassner biomass boiler controllers over Modbus TCP. It reads outside temperature, boiler temperatures, flow temperatures for heating circuits HK1, HK2, and HKA, buffer tank temperatures at top, middle, and bottom, system status for boiler, buffer, and heating circuits, boiler output and fuel consumption. Writes include target temperature for boiler, target flow temperatures for the three heating circuits, and buffer tank target temperature.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 27, read and write
- Brand
- Hargassner
- Key readings
- Outside Temperature · Boiler Temperatures · Actual Flow Temperatures HK1/HK2/HKA · Buffer Temperatures Top/Middle/Bottom · Status Boiler/Buffer/HK1/HK2/HKA · Boiler Output and Consumption
- Available commands
- Target Temperature Boiler A/1 · Target Flow HK1/HK2/HKA · Target Temperature Puffer
- Last updated
Registers (27)
21 read, 6 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Outside Temperature | °C | Read | |||
| Boiler Temperature A | °C | Read | |||
| Boiler Temperature | °C | Read | |||
| Actual Flow Temperature HK1 | °C | Read | |||
| Actual Flow Temperature HK2 | °C | Read | |||
| Actual Flow Temperature HKA | °C | Read | |||
| Status HK1 | Read | ||||
| Status HK2 | Read | ||||
| Status HKA | Read | ||||
| Status Boiler | Read | ||||
| Buffer Temperature Middle | °C | Read | |||
| Status Boiler A | Read | ||||
| Status Buffer | Read | ||||
| Control Status | Read | ||||
| Boiler Temperature 1 | °C | Read | |||
| Buffer Temperatur Bottom | °C | Read | |||
| Buffer Temperatur Top | °C | Read | |||
| Boiler Output | % | Read | |||
| Consumption | Read | ||||
| Storage Volume | Read | ||||
| Status Boiler 1 | Read | ||||
| Target Temperature Boiler A | °C | Write | |||
| Target Flow HK1 | Write | ||||
| Target Flow HK2 | Write | ||||
| Target Flow HKA | Write | ||||
| Target Temperature Boiler 1 | °C | Write | |||
| Target Temperature Puffer | °C | Write |
Loading registers…
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Use cases
- Pre-heat the buffer tank during a cheap electricity window (for systems that also include an electric backup element).
- Automatically drop heat curve output overnight to save fuel while keeping rooms comfortable.
- Alert the installer when boiler status indicates a malfunction or feed problem, common with pellet systems running damp fuel.
- Track fuel consumption per week or month to compare against invoiced pellet deliveries.
- Monitor buffer tank stratification to detect a failing mixing valve or pump.
Installation
Enable Modbus TCP in the Hargassner controller menu (engineer menu, contact the installer if locked).
Connect the Hargassner controller to the local LAN.
Note the controller IP and set a DHCP reservation.
In ModbusCloud, add a Modbus TCP device at the controller IP, port 502, slave ID 1.
Import the Hargassner template. All readings should appear within one polling cycle.
Things to watch for
Read registers are float32 but write registers are uint16. Why?
This is the Hargassner design choice. Reads report precise measured values with decimals, writes accept only integer setpoints. The template scales writes appropriately so you can enter target temperatures in degrees Celsius without thinking about the encoding.
Buffer tank top reads higher than the boiler. Is that a wiring mistake?
Not necessarily. If the boiler just finished a burn and entered clean-out, the buffer tank may briefly read hotter than the quickly cooling boiler. Persistent wrong ordering suggests a sensor swap, but a few minutes of inversion around a firing cycle is normal.
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