Home automation planning and costs

Thank you also to you, the tip about MDT was very helpful and insightful! Likewise, the hint regarding the software, although I still need to read up on what these "projects" then mean/can do. If that only means more effort with the same functionality, that would be IO

Please don’t misunderstand me, I don’t want to badmouth the system, quite the opposite. I want to form a proper opinion for decision-making.

And I want to help you form that opinion by dispelling the common belief that “KNX is a pharmacy.”

As O'Neill already said, you don’t have to opt for the “premium segment”… there are cheaper manufacturers especially for simple actuators and the relays inside all come from the same foundry anyway.

And also regarding the limit of 20 devices… just create multiple projects (i.e. several files in the software) such as one for the outdoor area, one for the ground floor, and one for the upper floor… then you can have 60 devices in your installation and manage everything with the 20-device version, just sequentially.

I had the electrician lay the cables/outlets for me, here I simply believe that I can use my time better (compared to many other homeowners) and then I carried out the rest of the KNX installation myself, meaning from here on:



So planning / purchasing / wiring / parameterizing the KNX components.

At the moment there are about 90 devices.

What’s against a KNX solution with small sub-distributions per room that house the actuators and thus greatly reduce the cabling effort and amount in the walls? Then you could also expand it step by step, as desire/time/money allow, which would make the whole thing much more attractive to me.

Basically nothing! Everyone as they like… this is again an advantage of KNX, you can set it up as you want as long as you comply with the standards.

However, I would then avoid actuators with loud relays… they do click quite loudly when switching… and that would personally bother me.

And what is the stance of relevant companies on the topic of DIY work in this area? Do you get approvals for self-wired but provider-planned systems?

That depends on the executing company. My partner let me intervene at every point and eventually accepted the system and basically granted approval. However, there are many who only offer full services because they are simply afraid—due to warranty issues—that someone else might botch things up.

A true knowledge pool here

One more critical question: Why can't (or can?) the power lines themselves be used as communication lines, similar to the powerline system in IT networks? That would greatly reduce retrofit capability and cabling effort.

Manufacturer: Thanks to KNX, they all have to be compatible with each other, right? Because especially the switches are really expensive, and those are needed the most. A cost-effective manufacturer would be very desirable.

The comparison chart seems a bit embellished at first glance. Of course, it would be all the better if that actually reflects reality later on.

There was a Powerline KNX line from B&J but it was discontinued because it was limited to one manufacturer and probably also due to lack of demand.

It simply isn’t worth it. The bus cable only costs about 30 cents per meter and for my entire installation it was under 100 euros, which is negligible. You just lay it everywhere, since it can be placed right next to power cables, and then you have BUS at every possible and impossible spot in the house. Which is also fail-safe and without additional hardware.

Yes, everything that the red-gray terminal on board has is compatible with each other.

I even pushed it to the extreme in some cases, simply out of curiosity. My B&J weather station runs with Merten software and receives data from a JUNG multisensor (actually according to all three manufacturers not possible) because compatibility is only given from the KNX terminal onwards.

The prices for pushbuttons are now moderate, you can also use conventional ones if you want. But then you need a flush-mounted pushbutton interface behind each, and functionality is somewhat limited, though you do save some money that way.

Or you can do it the other way around:

In a room with 3 roller shutters and a fireplace, you usually have 5 switches at the entrance: 1x RTR, 1x light, 3x roller shutters.

In total, the installation costs per drilled box are about 15 euros + switch insert 10 euros each + RTR 20 euros = 135 euros.

With KNX (if we stay with MDT) you need two boxes + KNX pushbutton with 8 functions and temperature sensor, so about 30 euros for drilling and 130 for the MDT pushbutton = 160 euros.

Yes, of course that’s 20% more, but the functionality also increases because you can do far more with the MDT pushbutton than with the simple one, and if you want to change something later, you only have to replace the pushbutton and don’t have to lay new cables.

Without RTR it obviously gets cheaper.

So my experience shows that the comparison chart is quite accurate... just a group switching of roller shutters conventionally costs a fortune. With KNX, just a few clicks.

Hello,

I am also a representative of the KNX faction.

I can only agree with Mycraft. I myself also use KNX and, like Mycraft, have bus cables AND flush-mounted conduit boxes with bus cables in all sorts of possible and impossible places. In every room, there is a box at the door at 2.0m, one at 1.5m, and the normal one at 1.15m. If later I want to install a motion, brightness, or whatever sensor, I just break open the box and that’s it. Additional effort minimal.

I can only agree with Mycraft on the costs as well. The 'expensive' part of KNX only starts when you begin with gimmicks. Simple KNX sensors (push buttons, thermostats, etc.) are in the range of 80-120€. And what you can already do with that is FAR beyond what you can do traditionally. And when wishes like 'central off,' 'central blinds,' multiple switching for hallway, staircase lights, etc., come along, it usually becomes more expensive than with KNX.

And if you have some money left over, you install a Synohr and talk to your house: status gimmick, cost 900€. The experience priceless!! When lying in bed and saying 'James Scene Sleep.' Blinds go down, lights slowly go out, soft music starts playing in the background, and the alarm clock is automatically activated depending on the entry in the calendar!!!

It's simply not worth it. The bus cable costs only about 30 cents per meter and for my entire installation it was under 100 euros, which really doesn't matter. You just lay it everywhere because it can be placed right next to power lines, and then you have BUS at every possible and impossible spot in the house. And that's also fail-safe and without additional hardware.

So what now, I thought preparing wasn't worth it? Then I'll just do a "normal" electrical installation, lay the KNX bus cable everywhere, and in 10 years gradually replace the components?