`disturbance_output` (C0049 / `ID_WEB_ZW2SSTout`) reports false fault when ZWE2 is active

[arclabch]

Description

The binary sensor disturbance_output (mapped to calculations.ID_WEB_ZW2SSTout, register C0049) produces false fault alerts whenever the second additional heat generator (ZWE2) is active, most notably during the weekly thermal disinfection cycle.

Root cause

The Luxtronik register ID_WEB_ZW2SSTout is a shared output for both:

• ZWE2 (Zusatzwärmeerzeuger 2 / Additional heat generator 2) activation
• SST (Sammelstörung / Collective fault signal)

The integration maps this register exclusively as a problem/disturbance indicator (BinarySensorDeviceClass.PROBLEM in binary_sensor_entities_predefined.py:60-64), but the register also goes true during normal ZWE2 operation.

Observed behavior

• Weekly thermal disinfection runs (e.g. 00:00–00:58), ZWE2 heats DHW to 60°C
• binary_sensor.luxtronik_*_disturbance_output goes ON for the duration
• Fault notifications are triggered
• Heat pump journal shows no error, there is no actual fault
• sensor.luxtronik_*_error_reason and its timestamp attribute remain unchanged

Expected behavior

The disturbance_output sensor should only report a problem when there is an actual fault, not when ZWE2 is operating normally.

Suggested fix

The integration should disambiguate by cross-referencing other registers when ZW2SSTout is true. For example:

• If C0095 (ID_WEB_ERROR_Time0, exposed as the timestamp attribute on error_reason) has not changed → ZWE2 is running, not a fault
• If C0069 (ID_WEB_Time_ZWE2_akt, ZWE2 timer) is counting up → ZWE2 is active

Alternatively, consider splitting the register into two entities:

• A binary_sensor for ZWE2 state (device_class: running): currently missing, only operation hours are exposed
• A computed binary_sensor for actual system fault

Workaround

A template binary sensor that cross-references the disturbance output with the error timestamp:

- binary_sensor:
    - name: "Heat Pump Fault"
      unique_id: heatpump_fault
      device_class: problem
      state: >
        {% set disturbance = is_state('binary_sensor.luxtronik_XXXX_disturbance_output', 'on') %}
        {% set disturbance_changed = as_timestamp(states.binary_sensor.luxtronik_XXXX_disturbance_output.last_changed, 0) %}
        {% set error_changed = as_timestamp(states.sensor.luxtronik_XXXX_error_reason.last_changed, 0) %}
        {{ disturbance and (error_changed >= disturbance_changed) }}

Related issues

• HP status idle when doing thermal disinfection #519
• Add missing sensors ID_WEB_HUPout, ID_WEB_ZW1out, ID_WEB_Zaehler_BetrZeitZWE2 #239

[rhammen]

@arclabch Can you implement your proposed changes and create a PR?