KNX and HA logic priority

Hardware
1

Dear HA community,

I am planning to build a new home and I would like to automate it.

After a few analysis I would like to go with a wired solution and I think to choose KNX.

One of the questions that I have is the following: I would like to have a basic logic imbedded in KNX (the dimmers and light switches should work) and a more advanced logic in HA. The idea is that if the HA server is up and running, the applied logic is the one from HA and not from KNX. If the server is down then the basic KNX logic should work.

Is that possible?

I thank you for your help and I hope my post is clear.

2

In theory, yes this is possible. In practice I think it’s best to use the right tool for each job - but it heavily depends on the actual function you want to implement and the used devices.

3

Thanks for the answer.

What I would like to do is use HA for scenario that are depending on the time of the day.

For instance I push the button on the KNX switch and if it is morning there is the morning routine starting.

Actually this is silly, the answer that you gave me is enlighting. The way to go could be the following:

-Basic logic is started trough certain KNX switches (dimmer and light switch mainly)
-Advanced logic is started trough other KNX switches (but those are only connected to KNX to server as an input to HA)

At this point it might be interesting to ditch KNX. I could have zigbee dimmer and switch and use the local control as a backup, zigbee would be use only for advanced logic!

4

Don’t ditch KNX. You do a new installation and you can do it properly.

I highly recommend to take a look at LogicMachine (https://openrb.com/).
In general try to keep the basic logics as low level as you can.

5

I also have a KNX installation, my reasoning was basic stuff needs to work from KNX itself, what I have from KNX itself:

  • Simple buttons on the wall turning on lights and activating shutters
  • Motion sensors in hallways and toilets
  • Lights turn on when smoke alarms are trigerred

HA does the more advanced stuff, such as triggering the ventilation modes (in KNX) based on humidity, time of day and room presence. Lights from KNX currently get turned on a low setting and get set by HA using adaptive lighting (I might want to change this at some point, if HA goes down, the lights work but have very little brightness).
I don’t really use scenes in HA nor KNX, but I have hooked up some KNX buttons to send commands to a group address, KNX doesn’t listen for that one, only HA does and acts accordingly

6

Another option (if your switches, dimmers and actuators support it), is set a blocking object on the KNX bus when HA is active. That way, you could block certain actions from happening if this object is active.

7

I’d rather not ditch a widespread wired system for a wireless - especially at the dawn of thread and matter.
Knx is a fine and solid System for your signaling path of switches and actuators. You can easily control your entire lighting, heating and shading devices. And there is a plethora of good looking switch/sensor devices available. I’d buy it again.

8

That is also the way I use it: Basic stuff is inside KNX, but HA has the UI/dashboard for everything (incl. KNX), my (light) scenes and my automation that e.g. turn the KNX controlled ventilation on and off at certain times, etc.

9

Many thanks for all the answers. Yes KNX is not off the table for me. Especially since I struggle to find zigbee dimmer and light switch that have a “clear” behavior in case the zegbee mesh is out, maybe someone has an idea regarding that?