Settings to Wolf CWL-2 with Ebusd-Adapter shield are overwritten by BM-2

[megawusl]

This is a question if anyone could solve the issue that using a BM-2 controller in parallel with an ebus adapter shield the BM-2 overwrites the ebusd adapter commands with the BM-2 settings.

Some background:
I have a Wolf CWL-2-325 ventilation system and a BM-2 controller connected via ebus. In addition I have connected an eBUS Adapter Shield v5 which is controlled by ebusd. So far everything is working fine. I can read the relevant values from my Wolf CWL-2 and publish them via MQTT using the ebus adapter shield.
Now the problem is as soon as I write a value via my ebus adapter like the Ventilator Mode using command "ebusctl hex 3c40cb0407010002", the value is written to the CWL-2 (address 3c) but overwritten by the BM-2 in regular intervals.
For instances: in the BM-2 I have set Ventilation mode "reduced" (BM-2 sends ebus command: 40cb0407010001 in regular intervals).
Now I send a write command from my ebus adapter shield which shall set ventilation mode "normal" (ebusctl hex 3c40cb0407010002). The command is confirmed with ok but a few seconds later the BM-2 is sending its current setting (again with a "40cb0407010001") which "overwrites" my ebus setting and sets back the ventilation mode to "reduced".

When I disconnect the BM-2 from the bus, the value set by the ebus adapter is persistent and all works fine. But I would like to keep the BM-2 connected as a central manual interface.

Does anyone faced the same issue and could find a solution?

[JonesGW-MGD]

I know nothing about Wolf equipment but in the Vaillant world it is similar - first, controllers repeatedly send settings not just on instantiation (in Vaillant world using SetMode) so you have contention with these devices. And also heating devices at least revert to defaults too after fairly short time periods.

So generally the 'hack' is to broadcast the control (in your case - ventilation mode) very frequently - minutes if not seconds using a HA automation or similar.

You might like to search the discussion forum for this similar pattern looking at 'SetModeOverride, and Set Mode' and 'replacing controller' to see if that helps with your understanding

[megawusl]

thanks a lot for the hint. I remember that I saw this hack, but for Vaillant and therefore simply did not think to try it with my Wolf...
However I confirm it is working for Wolf too.

Just in case someone else has a similar issue with Wolf CWL-2 (or the base Brink Flair 325) here is my final solution:
before sending a "ebusctl hex 3c40cb040701000x" message a "ebusctl hex 3c40ca0101" message has to be sent.

Thus I created a script with the following 2 lines for testing:
ebusctl hex 3c40ca0101
ebusctl hex 3c40cb0407010002

Where the last value (here a 2) has to be replaced with the value for the ventilation mode (0,1,2,3)

Running this script in a frequency of <20 seconds (because my BM-2 is sending its message every ~20 seconds) does set the required ventilation mode.

Another thing I've learned while testing:
when setting a different (to the set mode on the BM-02) ventilation mode directly on the display of the Wolf base device, it is not possible to change this mode from neither the BM-2 nor the ebusd. To be able to change the mode with the ebus, the ventilation mode set on the wolf base device needs to be set to the current ebus ventilation mode. Only then the display of the Wolf device is showing "Ebus" in the inner circle. And only then its possible to modify the setting with an external ebus master.