IDM idm
The IDM idm is a heat pump controlled by the IDM Navigator 2.0 unit, designed for residential and light-commercial heating, cooling, and domestic hot water production. This Modbus TCP template reads actual power consumption (address 4122), cumulative energy, and fresh water temperature (address 1014), and writes the PV surplus setpoint (address 74) so the Navigator 2.0 can direct surplus solar energy into heating and hot water loads. Connecting the IDM idm to your ModbusCloud Gateway gives installers continuous visibility into heat pump performance and enables solar self-consumption optimisation from a single portal.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 4, read and write
- Brand
- IDM
- Last updated
Registers (4)
3 read, 1 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| setmaxpower | kW | Write | |||
| power | W | Read | |||
| energy | Wh | Read | |||
| temp | °C | Read |
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Use cases
- Monitor actual heat pump power consumption to verify the unit operates within expected load bands across seasons.
- Track cumulative energy to calculate heating coefficient of performance over monthly or annual billing periods.
- Alert on unexpected drops in fresh water temperature to catch domestic hot water system faults early.
- Write PV surplus values to address 74 so the Navigator 2.0 automatically directs solar overproduction into heating loads.
- Compare power and energy readings against utility meter data to verify metering accuracy and detect billing discrepancies.
Installation
Enable Modbus TCP on the Navigator 2.0 controller: enter the installer service level, navigate to the building management or Modbus section, and set Modbus TCP to on. Assign the heat pump a static IP address to prevent address changes after router restarts.
Connect the IDM heat pump's LAN port to the same network switch as the ModbusCloud Gateway using a standard Ethernet cable. The network socket is located on the outside of the heat pump casing or inside the electrical compartment depending on your model.
In the ModbusCloud portal, add a new device, select the ModbusCloud Gateway as the data source, import the IDM idm template, and set the Modbus unit ID to 1 and port to 502.
Verify the connection by spot-checking the power register (address 4122) in the portal live-data view. A non-zero float value confirms the link is active. If the value stays at zero, confirm Modbus TCP is enabled and no IP address conflict exists on the local network.
Things to watch for
Port 502 is unreachable even though the heat pump web UI responds. Why?
Modbus TCP must be explicitly enabled in the Navigator 2.0 service level under the building management or communication section. The web interface and Modbus TCP run independently. Without this activation, port 502 stays closed even after a firmware update. Have a qualified installer enter the service menu and switch Modbus TCP on.
The gateway connects but register values appear sporadically or drop out. What now?
The IDM Navigator 2.0 is known to stop responding to Modbus TCP queries if the polling interval is too long. Users report that keeping at least one register polled every 10 to 13 seconds prevents the controller from entering a sleep-like state. ModbusCloud polls at most once per minute, every 5 minutes by default, so it cannot poll this often.
float32 values from the energy register look garbled or byte-swapped. How do I fix this?
The Navigator 2.0 transmits 32-bit floats as two consecutive 16-bit registers in big-endian byte order per the Modbus specification, but the word order follows the IEEE 754 float32s (swapped word) convention. If your values look incorrect, try the float32s decode mode in your client. The IDM template uses this layout for all float registers.
Is it safe to write to the setmaxpower register frequently from an automation?
Use caution. IDM documents that writable holding registers on the Navigator 2.0 store values in EEPROM, which has a maximum write cycle limit per register. Writing the same value repeatedly does not consume a cycle, but writing a continuously changing PV surplus value every few seconds will degrade the EEPROM over time. Debounce writes in your automation so you only send a new value when it changes by a meaningful amount.
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