Possibilities to integrate Wolf ventilation unit CWL 300


as a next step, I’m trying to integrate non-smart systems, like ventilation, into OH. The ventilation unit is a Wolf CWL 300 Excellent. Additional to the control unit on top of the unit, a second control unit, called BM-2, is installed. As far as I understood the manual correctly, then the BM-2 is connected via eBus.

The question is now, how to get that stuff into OH. First, I’m trying to get an overview about the different possibilites and their pro’s and con’s.

For me it is important, that I can switch between different fan speeds and to stop the fan (e.g. during summer time, to avoid warm air from outside; if a neighbor does BBQ; etc.). Additionally it would be nice, if I can see some status information in OH

Possible Solutions:

  1. step resp. multi-contact switch
    The manufacturer also provides the possibility to use an old-school 4-step-switch. Each step uses a defined fan-speed. Idea: This one could be (maybe?) simulated by a sonoff 4-channel smart switch.
  • Pro: Very cheap solution, about 30 EUR.
  • Con: No status information, just control fan speed via 4 steps. Turning the fan off is not possible (but maybe in combination with an shelly 1pm to power on/off?).
  1. Genuine Wolf Addon: Link Home
    The Link Home or Link Home Pro addons could also be used. In my case, it is probably (?) the pro version.
  • Pro: Optimal solution for Wolf products
  • Con: Too expensive, the pro version about 270 EUR.
  • Unkown: Turning the fan off is not possible?
  1. Raspberry and eBus-Coupler
    As far as I understood this thread correct, then using a Rasperry with eBUSd and an eBUS coupler could this job.
  • Pro: The coupler is about 130 EUR plus Raspberry (but I’ve always some spare Raspi’s here :wink:). From the OH perspective, I could use MQTT
  • Con: The BM-2 is already connected via eBUS (I’m not sure, if this is a problem).
  • Unkown: Turning the fan off is not possible?
  1. OpenTherm
    The manual says, that there is also an OpenTherm (OT) connection interface. I found some OT entries here, but I’m not sure, if the gateways are the same for ventilation units. Are there some experiences (config, costs, features)?

  2. Modbus / Genuine Wolf Addon
    Looks like, that there is also a Modbus interface available. Are there some experiences (config, features)?

  • Pro: ?
  • Con: Too expensive, about 270 EUR.

Are there some more possibilities?

Does anyone has some experiences? Pro’s and con’s?

Thank you!

It’s a shared bus, so you can connect multiple devices to it.

If you’re planning on using OpenTherm, the OpenTherm Gateway binding has support for heat recovery and ventilation units.

Thank you for the information. The wolf manual says, that it possible to continuously adjust the fan speed via OpenTherm (very good!). The only question for me is then, how to do the connection on the hardware level. The genuine wolf equipment is too expensive. Are there some alternative ideas for OpenTherm solutions?

Currently this thread is delayed by me, because I’ve several improvements for my openhab system in parallel :slight_smile: But after the others are done, then I’ll re-start this one!

The OpenTherm Gateway binding works with the OpenTherm Gateway designed by Schelte Bron. Schematics and part list can be found on his website if you want to assemble it yourself. There are also pre-built modules available like this one.

Please note that it seems that your ventilation unit is either eBus or Opentherm and not both at the same time. There is one connector on top. The BM-2 control module is specific eBus and not Opentherm. So if you want Opentherm, you probably also need another controller to control your ventilation if OpenHab is down.

Furthermore the ventilation unit does not allow switching ventilation off. It is possibly to power it down from the control panel at the unit itself, but that is meant to be able to clean/replace filters. Other remote controls (or eBus commands) do not seem to have this option. But then again, you can use the Shelly option in any case.