ᐅ Smart Home Building Control Systems / Home Automation / Bus Systems
Created on: 1 Sep 2016 13:15
M
Mycraft
This thread aims to shed some light on the topic...
Because it is becoming increasingly relevant, and the average builder is usually overwhelmed by the many offers, costs, possibilities, pitfalls, and problems involved in construction—especially when it comes to the topic of:
Modern electrical systems in the home during sales discussions. Since I live myself in a house with KNX electrical installation, I will also use examples to take a closer look at the KNX system.
Unfortunately, the term Smart Home is not protected. This results in any house with motion detectors or switchable wireless outlets from discount stores being defined as a Smart Home. It often happens that either only the bare minimum equipment is installed, or the salesperson is so enthusiastic about a certain system that, in the heat of the moment, people install devices that are completely outdated.
However, nothing here is smart... these remain "dumb" add-on components that simply increase comfort temporarily. Why temporarily? Because people are lazy, and eventually it becomes annoying to look for the remote control for the outlets, as it is always in a different place, and because motion detectors cannot be adjusted 100% to the needs of the occupants.
Every builder should become as familiar with their electrical system as with the choice of tiles or other elements of their future home. Too often, people rely on the general contractor (GC) to take care of everything.
If John Doe buys a motor vehicle today, he compares models for days, looks at features, and adds this and that to the wish list. No one wants a car without central locking or electric windows. Still, 20 years ago, it was perfectly normal—and these cars sold like hotcakes. It’s similar with home electrical systems today... you build a house, all options are open, and you could buy extras. But you opt out. Often due to lack of money, but also due to ignorance and entrenched ways of thinking, like “The switch does what it’s supposed to, it turns the light on and off.” What many don’t realize is that much more is possible. People may have heard somewhere that there is something out there, but they are absolutely unsure what, how, and why?
However, over the next 20 years, home electrical systems will likely develop as cars, phones, or televisions have. Nowadays, most people do not want cars without comfort features like central locking, nor phones with cords or CRT TVs.
A modern home electrical system typically looks like this:
The systems are interconnected via wireless or wired networks. They communicate using protocols and operate in the background without needing manual intervention. That means: the blinds automatically lower in strong sunlight to protect the house from excessive solar heat, or the skylight closes when it starts to rain.
Today we have access to a wide range of building automation technology that is available to everyone, unlike just a few decades ago.
We have simple systems with little or no intelligence, such as:
- Conventional electrical installations with push dimmers, impulse relays, etc.
Here, additional comfort is minimal, expandability is practically zero, and almost everything must be operated manually.
Mid-range systems, where many proprietary home automation solutions are found, include:
- Loxone
- Somfy Tahoma
- innogy Smart Home
- HomeMatic
- Philips Hue
- Apple HomeKit
- free@Home
Due to their limited functionality and generally less complex technology—especially regarding installation and programming—these systems tend to be cheaper than comparable building automation systems. The scope of functions and device packages should be carefully reviewed. Proprietary home automation systems are less flexible in terms of features and future expandability compared to building automation systems.
Then, there is the premium class of building automation technology (bus systems):
- LCN
- LON
- WAGO I/O
- Z-Wave
- KNX / EIB
These systems fulfill almost every wish and offer possibilities that many builders only dream of. However, they require thorough planning and are among the most expensive at first glance.
Compared to conventional installations and adding comfort functions in a conventional way, bus systems are becoming increasingly attractive and cost-effective.
Here is a graphic from a major German manufacturer with a presence in all sectors.
The idea behind building automation technology is:
- Integration of as many systems and components as possible (lighting, outlets, heating, ventilation, garden, television, sound system, etc.)
- Monitoring and control of systems from central points
- Expandability and flexibility
- Increase in comfort and ease of use
KNX offers the greatest integration of all systems because it is an open standard. This means the protocol is openly accessible, and all manufacturers who produce and sell KNX products must ensure their products comply with the KNX specifications. In other words, you can use existing experience, but the product must be designed so that it can be operated by any other KNX device from one or several manufacturers. This contrasts with proprietary systems (LOXONE, free@Home, Somfy, etc.), where you are tied to one manufacturer and thus become dependent on them. If production stops and devices in the house break down, you end up with expensive scrap and may have to start from scratch.
KNX is different. There are over 400 manufacturers and millions of products that all “speak” to each other. If a module fails, it is simply removed and replaced by another. It doesn’t matter which manufacturer the new module comes from, as long as it bears the KNX logo. KNX costs money, unfortunately. But as described earlier, the price decreases with the number of functions you want in the house. The debate about whether you need it or not is pointless here. The technology is available, and you have the choice. You can use it or not. As the saying goes: “You can get around by horse carriage too.”
An example:
If you have, for example, 15 roller shutters in the house and want them to be controllable not only locally at the window (without wireless), but also at central points (e.g., at the front door or in the bedroom), and if you want control on each floor, then the initial investment price becomes more reasonable. Because the additional components required for a conventional roller shutter installation (extra switches, separable relays, junction boxes) to provide this functionality are not free, and the labor to wire the shutters accordingly must also be paid for.
Because it is becoming increasingly relevant, and the average builder is usually overwhelmed by the many offers, costs, possibilities, pitfalls, and problems involved in construction—especially when it comes to the topic of:
Modern electrical systems in the home during sales discussions. Since I live myself in a house with KNX electrical installation, I will also use examples to take a closer look at the KNX system.
Unfortunately, the term Smart Home is not protected. This results in any house with motion detectors or switchable wireless outlets from discount stores being defined as a Smart Home. It often happens that either only the bare minimum equipment is installed, or the salesperson is so enthusiastic about a certain system that, in the heat of the moment, people install devices that are completely outdated.
However, nothing here is smart... these remain "dumb" add-on components that simply increase comfort temporarily. Why temporarily? Because people are lazy, and eventually it becomes annoying to look for the remote control for the outlets, as it is always in a different place, and because motion detectors cannot be adjusted 100% to the needs of the occupants.
Every builder should become as familiar with their electrical system as with the choice of tiles or other elements of their future home. Too often, people rely on the general contractor (GC) to take care of everything.
If John Doe buys a motor vehicle today, he compares models for days, looks at features, and adds this and that to the wish list. No one wants a car without central locking or electric windows. Still, 20 years ago, it was perfectly normal—and these cars sold like hotcakes. It’s similar with home electrical systems today... you build a house, all options are open, and you could buy extras. But you opt out. Often due to lack of money, but also due to ignorance and entrenched ways of thinking, like “The switch does what it’s supposed to, it turns the light on and off.” What many don’t realize is that much more is possible. People may have heard somewhere that there is something out there, but they are absolutely unsure what, how, and why?
However, over the next 20 years, home electrical systems will likely develop as cars, phones, or televisions have. Nowadays, most people do not want cars without comfort features like central locking, nor phones with cords or CRT TVs.
A modern home electrical system typically looks like this:
The systems are interconnected via wireless or wired networks. They communicate using protocols and operate in the background without needing manual intervention. That means: the blinds automatically lower in strong sunlight to protect the house from excessive solar heat, or the skylight closes when it starts to rain.
Today we have access to a wide range of building automation technology that is available to everyone, unlike just a few decades ago.
We have simple systems with little or no intelligence, such as:
- Conventional electrical installations with push dimmers, impulse relays, etc.
Here, additional comfort is minimal, expandability is practically zero, and almost everything must be operated manually.
Mid-range systems, where many proprietary home automation solutions are found, include:
- Loxone
- Somfy Tahoma
- innogy Smart Home
- HomeMatic
- Philips Hue
- Apple HomeKit
- free@Home
Due to their limited functionality and generally less complex technology—especially regarding installation and programming—these systems tend to be cheaper than comparable building automation systems. The scope of functions and device packages should be carefully reviewed. Proprietary home automation systems are less flexible in terms of features and future expandability compared to building automation systems.
Then, there is the premium class of building automation technology (bus systems):
- LCN
- LON
- WAGO I/O
- Z-Wave
- KNX / EIB
These systems fulfill almost every wish and offer possibilities that many builders only dream of. However, they require thorough planning and are among the most expensive at first glance.
Compared to conventional installations and adding comfort functions in a conventional way, bus systems are becoming increasingly attractive and cost-effective.
Here is a graphic from a major German manufacturer with a presence in all sectors.
The idea behind building automation technology is:
- Integration of as many systems and components as possible (lighting, outlets, heating, ventilation, garden, television, sound system, etc.)
- Monitoring and control of systems from central points
- Expandability and flexibility
- Increase in comfort and ease of use
KNX offers the greatest integration of all systems because it is an open standard. This means the protocol is openly accessible, and all manufacturers who produce and sell KNX products must ensure their products comply with the KNX specifications. In other words, you can use existing experience, but the product must be designed so that it can be operated by any other KNX device from one or several manufacturers. This contrasts with proprietary systems (LOXONE, free@Home, Somfy, etc.), where you are tied to one manufacturer and thus become dependent on them. If production stops and devices in the house break down, you end up with expensive scrap and may have to start from scratch.
KNX is different. There are over 400 manufacturers and millions of products that all “speak” to each other. If a module fails, it is simply removed and replaced by another. It doesn’t matter which manufacturer the new module comes from, as long as it bears the KNX logo. KNX costs money, unfortunately. But as described earlier, the price decreases with the number of functions you want in the house. The debate about whether you need it or not is pointless here. The technology is available, and you have the choice. You can use it or not. As the saying goes: “You can get around by horse carriage too.”
An example:
If you have, for example, 15 roller shutters in the house and want them to be controllable not only locally at the window (without wireless), but also at central points (e.g., at the front door or in the bedroom), and if you want control on each floor, then the initial investment price becomes more reasonable. Because the additional components required for a conventional roller shutter installation (extra switches, separable relays, junction boxes) to provide this functionality are not free, and the labor to wire the shutters accordingly must also be paid for.
Another advantage of a BUS installation is the ability to significantly reduce the size of large switch panels, which are now very common, without losing comfort or functionality. On the contrary, BUS switches often function as true control centers with their own timers, logic controllers, regulators, and displays.
for example:
can be replaced by something like:
or this:
or even this:
The possibilities are virtually limitless. They usually exist only in your mind or wallet.
With bus systems, you can replicate all the functions of a typical switch and, in the same space, control 2, 3... n other devices, display temperature, or even issue an alarm notification. Usually, the buttons can be assigned freely, and if your habits change, different functions can be made available with just a few mouse clicks and no extra cost. Or if you want a new design, you only have to remove the switch from the wall, replace it with a new one, reprogram it, and everything works again—no need to lay new power cables.
Many modern BUS switches also offer the familiar function of a conventional switch—just a single press to turn the light on. BUS switches often allow triggering any function by pressing multiple buttons simultaneously, for example, turning on the light.
Unlike conventional electrical wiring, bus systems separate actuators and sensors. This leads to great flexibility and functionality. You can trigger any number of actions from any sensor at any location. And if you add logic and automation beyond manual functions, actions happen automatically without any input from the occupant.
The light turns off automatically when you leave the room, or the lawn irrigation runs only until the soil is sufficiently moist. All this with feedback sent to the desired devices or locations in the house or even remotely.
No one is obliged to mount tablets on walls and navigate through countless menus until finding the right function. Everything can work without that, provided there is thorough planning. Although tablets look nice, they are only the second or third step in home automation. Large logic controllers like the GIRA Homeserver or Enertex EibPC and similar are also not strictly necessary for a modern electrical installation.
for example:
can be replaced by something like:
or this:
or even this:
The possibilities are virtually limitless. They usually exist only in your mind or wallet.
With bus systems, you can replicate all the functions of a typical switch and, in the same space, control 2, 3... n other devices, display temperature, or even issue an alarm notification. Usually, the buttons can be assigned freely, and if your habits change, different functions can be made available with just a few mouse clicks and no extra cost. Or if you want a new design, you only have to remove the switch from the wall, replace it with a new one, reprogram it, and everything works again—no need to lay new power cables.
Many modern BUS switches also offer the familiar function of a conventional switch—just a single press to turn the light on. BUS switches often allow triggering any function by pressing multiple buttons simultaneously, for example, turning on the light.
Unlike conventional electrical wiring, bus systems separate actuators and sensors. This leads to great flexibility and functionality. You can trigger any number of actions from any sensor at any location. And if you add logic and automation beyond manual functions, actions happen automatically without any input from the occupant.
The light turns off automatically when you leave the room, or the lawn irrigation runs only until the soil is sufficiently moist. All this with feedback sent to the desired devices or locations in the house or even remotely.
No one is obliged to mount tablets on walls and navigate through countless menus until finding the right function. Everything can work without that, provided there is thorough planning. Although tablets look nice, they are only the second or third step in home automation. Large logic controllers like the GIRA Homeserver or Enertex EibPC and similar are also not strictly necessary for a modern electrical installation.
Let’s now look at the structure of a KNX bus system.
KNX is a decentralized system. This means there is no central controller, no need for hubs, and no complicated wiring rules to follow.
Except for one: The bus cable, which connects to each device communicating over the bus, must not form a closed loop, as this would cause malfunctions.
Here you can see the difference between a conventional installation and KNX:
Conventional (left) vs. KNX (right)
In a typical home installation, a power line is usually run from a circuit breaker to each room. In that room, the electrician branches off power for sockets and lighting. The sockets are typically powered directly and wired in series. The lighting power line first goes to the switch; from there, it continues to the respective lamp. This ensures all loads are powered while minimizing installation effort. When the switch is flipped, it sends 230 V power to the lamp, causing it to light up.
In a KNX system, sensors and actuators are physically and electrically separated. This means the switch does not close the power circuit (as in conventional installations); instead, the actuator (a relay) in the distribution panel does. The switch only sends a command. This allows commands to be sent from various locations, and one or more actuators execute them. This reduces connection points and potential failure sources, greatly increasing the load capacity and safety of the electrical installation. Additionally, sockets, lamps, and other devices can be rewired quickly without opening walls to reassign a light switch, for example, to control multiple lights or devices.
Here is an example:
You can turn the same light on and off from any number of switches. It is only necessary to connect another switch to the bus cable and configure it. No additional changeover wiring or power cables are needed.
The smallest unit of a KNX network is the line. A line consists of a power supply, a KNX bus line, and the connected participants (devices). At least one participant must be a sensor, and at least one must be an actuator. The maximum number of devices on a line is determined by the capacity of its power supply. Using the strongest power supply variant with 640 mA continuous current, a maximum of 64 devices (assuming an average current consumption of 10 mA per device) can be connected to one line.
Most communication between bus participants takes place at the line level.
One line:
If more than 64 devices are needed, two or more lines (up to 15) can be linked into an area. The connection between individual lines and the common main line is made via line couplers. The line couplers on the main line must be powered by a separate power supply on the main line.
Line couplers serve two purposes: first, galvanic isolation between the line and the main line (so, for example, a short circuit on one line does not affect the main line); second, they filter telegrams sent over the main line to participants on other lines. Filtering reduces the volume of data transmitted on the network, as only telegrams destined for devices on a specific line are passed to that line and the main line.
Line couplers count as bus participants. Consequently, on a main line, in addition to the line coupler, only 63 other participants can be connected.
Multiple lines:
As you can see, the wiring is quite simple. Each bus participant gets one bus cable. Each line has its own power supply. Line couplers are placed between lines to enable communication. Using area coupling, KNX installations with up to 14,400 participants can be realized.
Approved bus cables recommended by ZVEI/ZVEH include types such as YCYM 2x2x0.8 or J-Y(St) Y 2x2x0.8. Bus cables compliant with the functional specification DIN V VDE 0829 Part 522 or EN V 50090-5-2 (for example, YCYM) may be laid together without restrictions with cables, wires, and conductors (for example, H07V) in electrical installation conduits.
Enough theory!
In a single-family home, there is usually one main line for the interior and a second line for the exterior. This keeps costs reasonable and prevents direct external access to the internal bus line.
Because KNX is decentralized, no central controller is required. Each KNX device can function autonomously. The minimum line setup, as already mentioned, consists of:
- Power supply with choke
- Sensor (switch/presence detector [PM]/etc.)
- Actuator
Due to this decentralized design, KNX devices can be connected anywhere in the system and are immediately ready for use after configuration—without running new cables or creating new power circuits. For example, a switch can be replaced by a presence detector, or a presence detector can be installed in parallel with a switch, or something else entirely.
If a KNX device fails (which is very unlikely), only the area that device controls will go offline. The rest of the installation remains unaffected and continues to operate normally. Simply replacing and configuring the device restores full functionality.
The high initial cost is partly due to the low failure rate. KNX was originally not developed for residential use but had to meet high standards because it is also used in sensitive industrial and commercial environments. Today, there are practically no large-scale installations without KNX. It is found in (Swedish) furniture stores, various department stores, airports, modern office buildings, and stadiums.
Here again is a direct comparison of how conventional and KNX-based automation are wired and how devices communicate:
On the left, conventional: Each system is independent and can only communicate with its own input/output devices.
On the right, KNX: All systems are connected via a bus cable and continuously communicate in the same language. Thus, every system "knows" in real time what another system is doing and what conditions currently apply.
For example, the heating does not have to wait to receive a "room too warm" message from the room thermostat; it knows earlier because the weather station has already reported "sunshine in the south."
KNX is a decentralized system. This means there is no central controller, no need for hubs, and no complicated wiring rules to follow.
Except for one: The bus cable, which connects to each device communicating over the bus, must not form a closed loop, as this would cause malfunctions.
Here you can see the difference between a conventional installation and KNX:
Conventional (left) vs. KNX (right)
In a typical home installation, a power line is usually run from a circuit breaker to each room. In that room, the electrician branches off power for sockets and lighting. The sockets are typically powered directly and wired in series. The lighting power line first goes to the switch; from there, it continues to the respective lamp. This ensures all loads are powered while minimizing installation effort. When the switch is flipped, it sends 230 V power to the lamp, causing it to light up.
In a KNX system, sensors and actuators are physically and electrically separated. This means the switch does not close the power circuit (as in conventional installations); instead, the actuator (a relay) in the distribution panel does. The switch only sends a command. This allows commands to be sent from various locations, and one or more actuators execute them. This reduces connection points and potential failure sources, greatly increasing the load capacity and safety of the electrical installation. Additionally, sockets, lamps, and other devices can be rewired quickly without opening walls to reassign a light switch, for example, to control multiple lights or devices.
Here is an example:
You can turn the same light on and off from any number of switches. It is only necessary to connect another switch to the bus cable and configure it. No additional changeover wiring or power cables are needed.
The smallest unit of a KNX network is the line. A line consists of a power supply, a KNX bus line, and the connected participants (devices). At least one participant must be a sensor, and at least one must be an actuator. The maximum number of devices on a line is determined by the capacity of its power supply. Using the strongest power supply variant with 640 mA continuous current, a maximum of 64 devices (assuming an average current consumption of 10 mA per device) can be connected to one line.
Most communication between bus participants takes place at the line level.
One line:
If more than 64 devices are needed, two or more lines (up to 15) can be linked into an area. The connection between individual lines and the common main line is made via line couplers. The line couplers on the main line must be powered by a separate power supply on the main line.
Line couplers serve two purposes: first, galvanic isolation between the line and the main line (so, for example, a short circuit on one line does not affect the main line); second, they filter telegrams sent over the main line to participants on other lines. Filtering reduces the volume of data transmitted on the network, as only telegrams destined for devices on a specific line are passed to that line and the main line.
Line couplers count as bus participants. Consequently, on a main line, in addition to the line coupler, only 63 other participants can be connected.
Multiple lines:
As you can see, the wiring is quite simple. Each bus participant gets one bus cable. Each line has its own power supply. Line couplers are placed between lines to enable communication. Using area coupling, KNX installations with up to 14,400 participants can be realized.
Approved bus cables recommended by ZVEI/ZVEH include types such as YCYM 2x2x0.8 or J-Y(St) Y 2x2x0.8. Bus cables compliant with the functional specification DIN V VDE 0829 Part 522 or EN V 50090-5-2 (for example, YCYM) may be laid together without restrictions with cables, wires, and conductors (for example, H07V) in electrical installation conduits.
Enough theory!
In a single-family home, there is usually one main line for the interior and a second line for the exterior. This keeps costs reasonable and prevents direct external access to the internal bus line.
Because KNX is decentralized, no central controller is required. Each KNX device can function autonomously. The minimum line setup, as already mentioned, consists of:
- Power supply with choke
- Sensor (switch/presence detector [PM]/etc.)
- Actuator
Due to this decentralized design, KNX devices can be connected anywhere in the system and are immediately ready for use after configuration—without running new cables or creating new power circuits. For example, a switch can be replaced by a presence detector, or a presence detector can be installed in parallel with a switch, or something else entirely.
If a KNX device fails (which is very unlikely), only the area that device controls will go offline. The rest of the installation remains unaffected and continues to operate normally. Simply replacing and configuring the device restores full functionality.
The high initial cost is partly due to the low failure rate. KNX was originally not developed for residential use but had to meet high standards because it is also used in sensitive industrial and commercial environments. Today, there are practically no large-scale installations without KNX. It is found in (Swedish) furniture stores, various department stores, airports, modern office buildings, and stadiums.
Here again is a direct comparison of how conventional and KNX-based automation are wired and how devices communicate:
On the left, conventional: Each system is independent and can only communicate with its own input/output devices.
On the right, KNX: All systems are connected via a bus cable and continuously communicate in the same language. Thus, every system "knows" in real time what another system is doing and what conditions currently apply.
For example, the heating does not have to wait to receive a "room too warm" message from the room thermostat; it knows earlier because the weather station has already reported "sunshine in the south."
Presence and Motion Detectors
PIR (Passive Infrared) or HF (High Frequency) detectors are essential components of an automated system, as they serve as its eyes and ears.
Without them, the system is blind and deaf and cannot respond to its surroundings or changes.
The simplest function of a detector is to trigger a pre-programmed response when a person is detected.
This usually involves the passive activation of light sources, which can vary depending on prior programming and ambient light conditions. However, the question of placement plays a crucial role, so that each detector is assigned to its specific application area.
PIR (Passive Infrared) or HF (High Frequency) detectors are essential components of an automated system, as they serve as its eyes and ears.
Without them, the system is blind and deaf and cannot respond to its surroundings or changes.
The simplest function of a detector is to trigger a pre-programmed response when a person is detected.
This usually involves the passive activation of light sources, which can vary depending on prior programming and ambient light conditions. However, the question of placement plays a crucial role, so that each detector is assigned to its specific application area.
This is how a building can be equipped where lighting control functions almost exclusively through occupancy sensors:
The occupancy sensor in detail
With this, you can not only automatically regulate the lighting but also save a significant amount of energy. The highly sensitive sensor can turn lights on and off throughout the entire day. The sensor passively reacts to changes in light and adjusts its functions independently. This means you don’t have to worry about forgetting to switch off the lights—once no movement is detected in the room, the light will turn off automatically via the sensor.
These sensors come in various designs, depending on their intended application, so you need to choose the appropriate one. Here are a few examples:
Standard 360° sensor
Flush-mount version for ceiling boxes:
For narrow and long rooms or specific areas:
For wall boxes:
The occupancy sensor in detail
With this, you can not only automatically regulate the lighting but also save a significant amount of energy. The highly sensitive sensor can turn lights on and off throughout the entire day. The sensor passively reacts to changes in light and adjusts its functions independently. This means you don’t have to worry about forgetting to switch off the lights—once no movement is detected in the room, the light will turn off automatically via the sensor.
These sensors come in various designs, depending on their intended application, so you need to choose the appropriate one. Here are a few examples:
Standard 360° sensor
Flush-mount version for ceiling boxes:
For narrow and long rooms or specific areas:
For wall boxes: