Slots in Poroton T12

What do you mean by centrally switching, [Stromstoßrelais]??? Otherwise it doesn't make sense, since the lamps are usually wired at the switch. However, I also have a supply line from the meter cabinet to the switch for a maximum of 2 lamps each, of course in a conduit... Same for sockets, just the sockets in the living area have 3 supply lines with corresponding 3 fuses.

What do you mean by centrally switching, relay???

If you mean the actuators by relays, then yes.

Otherwise it doesn't make sense, the lamps are usually wired at the switch. However, I also have a supply line from the meter cabinet to the switch for a maximum of 2 lamps each, of course in conduit...

That is one of the two main differences. All switches, or motion detectors (sensors) require an additional line (bus, or KNX cable, the green wire), otherwise the wiring can remain the same.

Sockets as well, just the sockets in the living area have 3 supply lines with 3 corresponding fuses.

And here we have the second difference. For a normal room size (except kitchen), the electrician might have made two circuits. One for lighting, one for three sockets in three corners of the room. As preparation for KNX, he has to wire each socket separately from the distribution board.

If you read about wiring for KNX on the web, mostly KNX proponents talk about simplified installation effort. If you talk to an electrician, they say higher costs due to increased installation effort. I consider the installation effort to be the same (excluding materials); the technician just has to think more during laying and especially during connecting, because KNX is not commissioned that often.

Back to the topic.

Even if I had laid the cables to the sockets, with or without KNX, in the Poroton wall (not suspended ceilings) without conduit (in case of uncertainty, instead of 3x1.5 use 5x1.5 to possibly expand later), if someone wants a conduit to the socket, then google "Fränkische cable protection conduit".

The hardware store cable protection conduits are single-walled, meaning the inside is just as angular as the outside. "Fränkische cable protection conduit" is double-walled, outside angular, inside rounded. This makes it much easier to pull a cable through.

Although, when preparing for KNX, I would pull KNX cables in immediately. When replacing cables, cables are pulled from the front and pushed from the back at the same time, which is already difficult enough. If a conduit is laid empty, there is a risk that it is narrowed somewhere, e.g., due to too small a radius. Then even the best conduit won't help.

3 x 1.5??? nah, for me only 2.5

Sockets as well, the sockets in the living area alone have 3 feed lines with accordingly 3 fuses.

3 x 1.5??? no, for me only 2.5

Who advised you? Did you have 2.5 sqmm laid for each individual socket? If a suitable 20A circuit breaker was installed for the cross-section, you can now connect devices of up to 4.4 kW instead of up to 3.5 kW.

From 9/2017 onwards, a new vacuum cleaner is not allowed to have more than 900W, the current ones no more than 1600W. What do you intend to connect to your sockets?

Who advised you?
Did you have 2.5 sq mm installed for each individual socket?
If a suitable 20A circuit breaker was installed for the cross-section, you can now connect devices up to 4.4 kW instead of up to 3.5 kW.

Since 9/2017, a new vacuum cleaner is not allowed to exceed 900W, the current ones no longer 1600W.
What do you intend to connect to your sockets?

??? There are not only 3 sockets in the living area, I was talking about 3 supply lines. Of course, each has several sockets.
Apart from that, you can’t generally say that a 2.5mm² cable can be protected with 20A; it depends on the length of the cable and the corresponding resistance. If you install 1.5 and this is a longer supply line and you daisy chain 4-5 sockets, you are quickly at the limit of what is allowed.
For example, our stairwell lighting runs once from the basement to the attic and back. With 1.5mm², a 16A fuse was out of the question.
I don’t know to what extent the regulations differ from federal state to federal state, but I wouldn’t save on cables—that is, the things you don’t want to replace.
Besides, only vacuum cleaners with the corresponding power are no longer allowed to be sold, but do you immediately buy a new vacuum cleaner, washing machine, dryer, hairdryer etc. because of that?

You are right and I am wrong.

It is good that several sockets were installed; most multi-socket outlets are only approved up to 3500W.

I was aware that the resistance depends, among other things, on the length of the cable. Thank you.

For the limit of what is allowed, the number of sockets is not decisive. For the number of circuits for lighting and sockets in a residential building, the living area is decisive. Up to 50 sqm, two are sufficient.

I don’t know why your stair lighting was rerouted and why 16A and 1.5 sqmm were out of the question; most stair lights are LEDs with about 1W power. I wouldn’t recommend more than one LED per 1 meter anyway; it gets far too bright at night in the stairwell.

Of course, you are right, one should not save on electrical work, insulation, or other building materials. Everyone should keep their budget in mind; whether to oversize one or several trades is up to each person. If there are special reasons for it, why not.

Separate lines have been laid for my washing machine, dryer, and hairdryer.