ᐅ Bus systems – wiring, planning, and more?

Tarnari schrieb:

...
Truly high data rates with wireless on a consumer level only work at distances of about 1-2 meters (3-6 feet) at most.

Example measurements from the day before yesterday:
FritzBox 7530 behind a Vodafone cable router to a Note 10+ smartphone

Connection 500/50 Mbit/s
Measurement at about 1 meter (3 feet) distance: 440 Mbit/s
Measurement at about 15 meters (49 feet) distance: 45 Mbit/s
(From the utility room to the terrace, no walls or windows in between, or open (shell construction))

And: Flexible cables are generally always used from the LAN socket to the end device. Always!

@rick2018
Power outlets can be easily extended, allowing you to operate an "unlimited" number of devices. In a bus system, the layout is star-shaped, so only one end device is connected per outlet.

@superzapp
Those are poor values. However, it’s still not an issue because a real 45 Mbit/s is more than enough for virtually any household device or control system.

But another question: The bus system also carries the power supply, right? Could every outlet then be connected using just a bus cable, eliminating the need for a conventional power cable? In other words, is there a type of wall socket that can operate uncontrolled but still allow you to connect an end device later?

Also, what happens in case of a short circuit? In a normal power network, usually nothing happens—at worst a fuse blows. But the control unit of a bus system is probably more expensive than a $10 fuse. Or is there a similar type of protection upstream so that the system can never be damaged? How does it behave during a lightning strike?

AleXSR700 schrieb:

With the bus system, it has a star-shaped topology.

Now you're making me curious

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

AleXSR700 schrieb:

The bus system is a star topology. So only one end device per connection.

No, that is not entirely correct. You can connect as many end devices as the cable, actuator, and circuit breaker allow, and you can of course reconfigure them on the bus quickly and anytime as needed.

There are many different variants of bus topologies. Depending on the bus type, it can be a star, tree, ring, open ring, or various combinations of all these forms.

AleXSR700 schrieb:

The bus system also includes power supply, right? Could you then connect every socket outlet by bus cable and skip the "normal" power cable?

No, because a bus usually uses SELV voltage—that is, some kind of low-voltage variant. So you obviously cannot operate a TV or toaster with it. However, running bus cables to the sockets is not a bad idea, as it always allows you later to make any socket switchable, monitorable, etc. Or you can remove the socket at a certain location and instead install a sensor, detector, or probe.

Of course, there are more or less unusual solutions today, such as Digitalstrom, which use the 230V cables for communication and thus do not require separate bus cabling. But this approach comes with other significant disadvantages.

AleXSR700 schrieb:

So, is there some kind of wall socket that can operate unswitched but later allow connecting an end device?

In a well-planned bus cabling system, this is the standard. Each socket can usually be supplied with permanent power or easily made switchable with just a few adjustments.

AleXSR700 schrieb:

One more question: What happens in the case of a short circuit? Usually, in a normal electrical system, nothing major. At worst, a fuse blows. But the control unit of a bus system is probably more expensive than a $10 fuse.

Typically, bus components are short-circuit resistant. That means nothing happens. You fix the short circuit, and the system resumes normal operation.

Of course, you cannot foresee every fault, and failures do occur. However, a short circuit in modern systems is often dramatized, with some consultants encouraging trusting homeowners to buy expensive additional protective devices against it.

AleXSR700 schrieb:

Or is the same kind of protection installed that prevents damage to the system?

It depends on the system, but basically, very little can go wrong.

AleXSR700 schrieb:

How about lightning strikes?

This is more serious, of course. Depending on how the installation is protected, the result can range from a total system failure to "did anything happen at all?"

You can also connect a long cable to your network outlets and/or extend them.
Apparently, you don't mind having a cable running through the room. However, that doesn't quite match your statement about the final positions...
You have now read the same opinion several times, including from professionals in the field.
Bus systems are not star-shaped.
I also don’t understand why you are so resistant.
Wireless is possible but more expensive. In new construction, cables are installed more securely and provide a significantly faster network.
The cost of cabling is negligible.
I would like to learn more about your building project. Are you equally “enthusiastic” and “innovative” in other areas of the construction?
No one here has said, “this is done this way just because it always has been,” but has explained why it should be done that way.

Hi,
no, I’m not a fan of cables running across the room either. But I would prefer a single power cable rather than potentially adding a bus cable as well.
However, if the bus system doesn’t have to be star-configured, then my statement is obviously incorrect. In that case, the cable can be moved to a new location just as easily as the power cable. If it were star-configured, you would have to run a new cable through the entire house.
I understood that only one actuator is allowed per line, which is why a star topology is necessary. And that’s exactly what I found extremely complicated.

So, sorry about that. If KNX doesn’t have to be star-configured, it’s obviously much easier. Would it be enough then to lay one bus cable per room and route it from power outlet to power outlet within that room? And could the bus cable be tapped off at each outlet while still allowing multiple actuators on the same line?

By the way, my confusion came from web searches and MyCraft’s statement (no blame intended! Definitely my mistake):
No, exactly the opposite is true. They try to sell simpler solutions. It hardly gets easier than KNX. Star wiring and bus cable, and then everything is switchable, remotely controllable, etc., even via radio if you add an interface.