Add a ventilation mode select entity for Duco

[ronaldvdmeer]

Summary

Add a select entity that exposes supported Duco ventilation states directly.

Problem

The current fan entity provides simplified control. That is useful for basic interaction, but it does not expose the full set of supported ventilation states in a clear and explicit way.

Scope

Add a select entity for supported ventilation states.

The exact list should be derived from supported device capabilities and client models, and may include states such as:

• AUTO
• AUT1
• AUT2
• AUT3
• MAN1
• MAN2
• MAN3
• CNT1
• CNT2
• CNT3
• EMPT

Requirements

• keep the existing fan entity behavior stable
• avoid exposing unsupported or invalid states
• make sure the select reflects the current device state accurately
• avoid an ambiguous overlap between the fan entity and the select entity

Acceptance criteria

• a select entity is added for supported devices
• selecting an option updates the device state successfully
• entity state stays in sync with device changes
• tests cover state mapping and device updates

[ronaldvdmeer]

Update: select platform abandoned - fan presets extended instead

During implementation of the select entity, I ran into several fundamental design problems that led me to take a different approach. This comment documents the full reasoning.

Problem 1: AUT1/2/3 are not selectable states

AUT1, AUT2 and AUT3 look like regular ventilation states in the API model, but they behave differently. When you write one of them to the device, the device immediately transitions to AUTO with an adjusted target flow. They are one-shot commands, not persistent states.

This breaks a select entity completely. The moment you pick "Automatic boost (15 min)", the device reports back AUTO. The select would have to either keep showing AUT1 (wrong - the device is in AUTO), or flip back to AUTO immediately (confusing - the user just selected something and it reverts). There is no way to represent these as stable options in a select without misleading the user.

Problem 2: CNT1/2/3 already have a UI control

The fan entity exposes a speed percentage slider that maps directly to CNT1 (33%), CNT2 (66%) and CNT3 (100%). Including these in a select as well would give two independent controls for the same states, which is an overlap that Home Assistant core reviewers specifically flag as undesirable. The fan entity owns the speed slider; that does not belong in a select.

Problem 3: the overlap problem is not solvable cleanly

After removing AUT1/2/3 (not stable) and CNT1/2/3 (already on the slider), the remaining writable states are: AUTO, MAN1, MAN2, MAN3, EMPT. These are exactly the states that make sense as preset modes on the fan entity.

Home Assistant's FanEntity has first-class support for preset modes. They represent named operating modes, which is precisely what AUTO / MAN1-3 / EMPT are. Putting them into a separate select entity would add an extra entity without adding any new capability.

Solution: fan presets (in progress)

I extended the fan entity with five preset modes:

Preset	Duco state written	Meaning
auto	AUTO	Hand control back to Duco's algorithm
man1	MAN1	Manual continuous low speed
man2	MAN2	Manual continuous medium speed
man3	MAN3	Manual continuous high speed
empt	EMPT	Empty house / away mode

The speed slider (33/66/100%) remains for CNT1/CNT2/CNT3. When a preset is active, percentage returns None, so the slider and preset buttons never conflict.

Timed variants (MAN1x2, MAN1x3, etc.) set externally - for example via a wall switch - are read correctly and displayed as their corresponding base preset label. Writing is always done via the base variant; for timers, an HA automation with a delay is the right tool.

What is NOT included, and why

• AUT1/2/3 - one-shot commands, not stable states. Cannot be represented in a select or preset without misleading the user.
• MAN1x2, MAN1x3, etc. - timed variants. Readable (mapped to their base preset), not writable via the UI. Timers belong in automations.
• CNT1/2/3 - already exposed via the speed slider. Not duplicated as presets.

Status

The fan preset implementation is complete on branch feat/duco-fan-ventilation-presets. This issue stays open until the corresponding PR is merged.

[ronaldvdmeer]

PR submitted: home-assistant#169685

[ronaldvdmeer]

Edit — correcting the table and status in the comment above.

The preset descriptions had a wording error: MAN1/2/3 are timed states (the device returns to AUTO when the timer expires). CNT1/2/3 are the continuous overrides. Updated table:

Preset	Duco state written	Meaning
auto	AUTO	Hand control back to Duco's algorithm
man1	MAN1	Manual low speed (timed — device returns to AUTO after the configured timeout)
man2	MAN2	Manual medium speed (timed)
man3	MAN3	Manual high speed (timed)
empt	EMPT	Empty house / away mode

The speed slider (33/66/100%) maps to CNT1/CNT2/CNT3, which are continuous overrides with no time limit.

Status update: PR is now open: home-assistant#169685