Known Limitations

Device Compatibility

Navigator 10 has direct maintainer hardware confirmation. Navigator 2.0 and Navigator Pro are expected from the typed register model but still need complete diagnostics across current firmware variants.
Older IDM controllers without Navigator firmware are not supported
Modbus register mapping may vary slightly between firmware versions

Only Modbus TCP is supported (no serial Modbus RTU)
Port and Slave ID must be configured correctly
Some controller/firmware combinations tolerate only limited parallel Modbus clients. If timeouts correlate with another automation system, test with that client stopped or increase the polling interval

Some Modbus registers are backed by EEPROM storage on the controller and tolerate only limited write cycles over the hardware lifetime.
The integration logs a warning when the same register address is written more than once within 5 seconds, which helps catch runaway automation loops.
For the raw write_register service, users must acknowledge the risk explicitly. No automatic hard-block prevents frequent EEPROM writes — treat unknown addresses with care.

Multiple IDM heat pumps are supported. Each connection must have a unique host, port, and slave-ID combination.
For multiple heat pumps on the same bus: use separate Slave IDs and create a separate entry for each

Some registers are read-only (e.g., energy meters, temperature sensors)
Attempting to write to read-only registers may return a Modbus error
The write_register service deliberately permits an explicitly acknowledged custom address, but still validates datatype and numeric encoding. It cannot infer safe ranges, EEPROM behavior or semantics for unknown addresses — for experienced users only

A maximum of 10 zone modules with up to 8 configurable rooms each is supported. Six rooms is the current Navigator 10 default; only configure physically present rooms.

Navigator 10 has direct maintainer hardware coverage.
Navigator 2.0 and Navigator Pro remain dependent on complete community diagnostics across firmware variants.
A responding probe address alone may not prove an optional feature exists; unavailable sentinels are considered where hardware evidence exists.
See Stability & Release Readiness for the current blockers before removing the beta label.
Zone module configuration is adjustable via options after initial setup
Rooms without a physical sensor may return -1.0 as a value (marked as unavailable)

Home Assistant state is updated through scheduled Modbus and optional web refreshes. The integration does not currently expose unsolicited controller events as immediate Home Assistant push updates.
Changes made elsewhere become visible after the relevant refresh interval.

The current firmware version is read as a diagnostic sensor (firmware_version)
Firmware updates directly from Home Assistant are not possible
Updates are done via the myIDM cloud portal or via a USB stick using the controller display's service menu (unlocked with the Fachmann Ebene codes the integration can calculate).
The three local interfaces exposed by the controller (Modbus TCP 502, Navigator HTTP 80, Navigator 10 WebSocket 61220) do not carry any firmware-update endpoint. All candidate WebSocket controllers (firmware, update, upgrade, software, usb, upload, maintenance, system.update, system.firmware, system.software, system.usb) respond with provided controller [...] is not supported!. See Navigator Protocol Analysis for the full verified controller catalog.

Web connection as the core path: Modbus operation does not depend on a web login. The optional read-only supplement uses the supported local Navigator HTTP or WebSocket session and can provide a limited web-only fallback.
Global force_update: Not enabled by default. External time-series systems should use recorder/InfluxDB configuration or selected helper sensors to avoid unnecessary Home Assistant database load.