Daikin Heating & Cooling
Controls Daikin Altherma heat pumps via Modbus TCP or RTU through the HomeHub interface.
This ModbusCloud template controls Daikin Altherma 3 heat pumps through the Daikin HomeHub (EKRHH) interface over Modbus TCP (also supports Modbus RTU). It reads electrical power, flow and return temperatures, outside temperature, hot water storage temperature, flow rate, and heat pump error codes. Writes include operation mode, heating and cooling target flow temperatures, hot water storage target temperature, and room target temperatures. Requires Daikin MMI2 firmware 7.3.0 or higher.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 42, read and write
- Brand
- Daikin
- Key readings
- Heatpump Electrical Power · Flow and Return Temperatures · Outside Temperature · Hot Water Storage Temperature · Flow Rate · Heatpump Error Code and Sub Code
- Available commands
- Heatpump Operation Mode · Heating/Cooling Target Flow Temperatures · Hot Water Storage Target Temperature · Room Target Temperatures
- Compatible models
- Altherma 3 H HT · Altherma 3 H MT · Altherma 3 R · Altherma 3 R MT · Altherma 3 M
- Last updated
Registers (42)
31 read, 20 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| 38 State Heatpump Operation Mode | Read | ||||
| 21 State Heatpump Error | Read | ||||
| 32 State Heatpump Electrical heater | Read | ||||
| 23 State Heatpump Error Sub Code | Read | ||||
| 30 State Hot Water Circulationpump [PZ] | Read | ||||
| 31 State Heatpump Compressor [C] | Read | ||||
| 33 State Disinfection Operation mode | Read | ||||
| 35 State Defrost/Starting Operation mode | Read | ||||
| 36 State "Hot" Start | Read | ||||
| 37 State 3-Way Valve Heat+Cool/ Hot Water [3UV1] | Read | ||||
| 40 Actual Heatpump Flowtemperature after PlateHeatExchanger [PHE] | °C | Read | |||
| 41 Actual Heatpump Flowtemperature after Backupheater [BUH] | °C | Read | |||
| 42 Actual Heatpump Return Flowtemperature | °C | Read | |||
| 43 Actual Hot Water Storage Temperature [tWW] | °C | Read | |||
| 44 Actual Outsidetemperature [tAU] | °C | Read | |||
| 49 Actual Heatpump Flow Rate [E] | l/h | Read | |||
| 50 Actual External Roomtemperature | °C | Read | |||
| 51 Actual Heatpump Electrical Power | kW | Read | |||
| 52 State Hot Water Operation mode | Read | ||||
| 53 State Heating/Cooling Operation mode | Read and write | ||||
| 54 State Target Mainheating Flowtemperature Lower limit | °C | Read and write | |||
| 55 State Target Mainheating Flowtemperature Upper limit | °C | Read and write | |||
| 57 State Target Maincooling Flowtemperature Upper limit | °C | Read and write | |||
| 56 State Target Maincooling Flowtemperature Lower limit | °C | Read and write | |||
| 58 State Target Addheating Flowtemperature Lower limit | °C | Read and write | |||
| 59 State Target Addheating Flowtemperature Upper limit | °C | Read | |||
| 60 State Target Addcooling Flowtemperature Lower limit | °C | Read | |||
| 61 State Target Addcooling Flowtemperature Upper limit | °C | Read | |||
| 10 State Hot Water Storage Targettemperature | °C | Read and write | |||
| 2 State Cooling Target Supply Flowtemperature | °C | Read and write | |||
| 1 State Heating Target Supply Flowtemperature | °C | Read and write | |||
| 3 Heatpump Operation Mode | Write | ||||
| 6 Heating Room Targettemperature | °C | Write | |||
| 7 Cooling Room Targettemperature | °C | Write | |||
| 4 Space Heating/Cooling Operation Mode | Write | ||||
| 9 Heatpump Quiet Mode Operation mode | Write | ||||
| 12 Hot Water Storage Operation mode | Write | ||||
| 13 Hot Water Storage Electrical Heater Operation mode | Write | ||||
| 63 Offset Weather Operation Mode Heating Supply Flow Targettemperature | °C | Write | |||
| 65 Weather Operation mode HC2 | Write | ||||
| 66 Offset Weather Operation Mode Heating Supply Flow Targettemperature HC2 | °C | Write | |||
| 67 Offset Weather Operation Mode Cooling Supply Flow Targettemperature HC2 | °C | Write |
Loading registers…
Send your device list
If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Raise Altherma hot water setpoint during cheap electricity hours and lower it during peak tariffs.
- Override the heat curve from an external building management system during events or occupancy changes.
- Track instantaneous COP using electrical power read from the heat pump compared to thermal output computed from flow, return, and flow rate.
- Alert the installer when the error code becomes non-zero, with sub code included for faster diagnosis.
- Integrate Altherma with external room temperature sensors by writing Room Target Temperature values from a ModbusCloud automation.
Installation
Confirm the Altherma 3 MMI2 firmware is 7.3.0 or newer. Update if needed via the Daikin service tool.
Install the Daikin HomeHub (EKRHH) following UseCase 3 of the HomeHub installation manual. This wiring case enables the full Modbus register set.
Configure the HomeHub for Modbus TCP or Modbus RTU per your installation topology.
In ModbusCloud, add a Modbus TCP or RTU device targeting the HomeHub.
Import the Daikin Heating and Cooling template. Readings start within a polling cycle and writes can be tested by changing operation mode.
Things to watch for
I installed the HomeHub but some registers return zero or errors. What to check?
Confirm you used UseCase 3 during HomeHub commissioning. Other wiring cases expose a smaller register set. If you installed UseCase 1 or 2, you need to rewire to UseCase 3 to get full access.
Which heat pump models work with this template?
Daikin lists Altherma 3 H HT, 3 H MT, 3 R, 3 R MT, and 3 M. Check the HomeHub installation manual for the current compatibility list. Altherma LT (1st generation) and older indoor units are not supported.
Room Target Temperature write has no effect on the indoor climate. What now?
The zone needs to be configured for external control in the Altherma installer menu. Without this, the heat pump ignores room setpoint writes and uses its own control logic.
Want to see how it works?
