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. Increase polling frequency or add a keep-alive register to the template schedule.

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.

Free Modbus template: 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.

Name	Address	Function	Type	Unit	Access
setmaxpower PV surplus power setpoint written to the heat pump, in kW.	74	FC16	float32	kW	W
power Actual electrical power consumption of the heat pump.	4122	FC03	float32	W	R
energy Cumulative electrical energy consumed by the heat pump.	4128	FC03	float32	Wh	R
temp Fresh water draw-off temperature at the domestic hot water tap.	1014	FC03	float32	°C	R