Power supply

Find out here how to supply your KNX bus system with power. What power requirements do the individual KNX participants have? Which items do we recommend? This eibabo catalog contains power supplies and system devices for various automation systems, such as LCN, radio bus, KNX and many other systems.

How do I determine the right KNX power supply for my installation?

The most common power supplies in this catalog are for the KNX bus system. To determine the required power supply, you should first look at the structure of a KNX network. A distinction is made here between segments that are divided into a specific hierarchy. Imagine a tree whose trunk splits into branches. Twigs come off the branches. The branches represent the smallest 'unit' and are referred to as lines in the KNX network. Each line consists of the power supply, a KNX bus line and the participants. A main line would be the branch that connects multiple lines into an area. The area line represents the trunk that connects multiple areas. This structure makes sense for larger networks or if a division into several segments is recommended due to the structural conditions of a building.

In addition to the power supply for the participants, the bus itself also requires a power supply of 24V nominal voltage. This is transmitted along with the data signals on the bus line. Depending on the manufacturer, the corresponding power supplies deliver 28V to 31V slightly more than the nominal voltage. This creates a buffer, for example for possible line losses. KNX bus participants still work stably up to 21V. The voltage difference is used to compensate for voltage drops in the bus line or at the contact resistances. A line can theoretically include up to 64 devices and provides a maximum current of 640mA at a voltage of 28V to 31V. This statement is based on the assumption that each KNX participant is allowed a maximum of 10mA from the bus voltage. The load capacity of the strongest power supply of 640mA continuous current must not be exceeded.

Please plan in reserve

When dimensioning your lines, allow at least 15% buffer for later extensions. A 640mA power supply therefore corresponds to around 54 devices.


Smaller KNX power supplies are also available for fewer participants per line. If you know in advance that a line will never have more than a maximum of 32 subscribers (27 with buffer), you can choose a 320mA power supply. The same applies to a line with a maximum of 16 devices (14 with buffer). A 160mA power supply is sufficient here. In addition, there are larger 29V-30V power supplies with current limiters 640mA and KNX chokes separately. A KNX power supply always contains a KNX choke.

The power requirement of a KNX participant is usually standardized. This should not normally exceed 200mW. 150mW for power supply of the microprocessor and 50mW for the bus terminal. There are many KNX devices that do not require this power reference. There are also KNX participants with higher requirements, for example KNX actuators, KNX room controllers or KNX displays. Please take this into account when sizing your lines. Pay attention to possible voltage drops, because the devices do not draw a certain current from the bus, but a certain power. If the maximum current is expected to be exceeded, you should integrate fewer than 64 participants in this line.

How does the KNX power supply work?

In the KNX power supply, the power supply always provides direct current (DC) at the output. The difference between the designation transformer and power supply is essentially that a classic transformer always outputs alternating current (AC) and also only works with alternating current at the input. Depending on the manufacturer, the power supplies generate a supply voltage of 28V to 31V. When the bus is idle, the supply voltage of the power pack is present. This state corresponds to a logical '1'. The logical '0' is generated by an alternating voltage. In order to send the '0', the sending KNX device reduces the voltage by around 5V for a short time. This results in an immediate compensating impulse, which comes from a choke integrated in the power pack. The KNX line is thus decoupled from the associated KNX power supply by the choke. This prevents short circuits in the data telegrams caused by the power pack. The voltage change is necessary so that the recipient can use the information

Are there KNX power supplies for more than 64 participants per line?

In the eibabo® technology store you will find KNX power supplies up to 1280mA. However, it is not possible to set up a line with 128 participants. The power is distributed at two different outputs. There is thus the classic choked output with 640mA for the KNX bus as well as another unchoked output. Participants can be supplied with an auxiliary voltage via this output, for example a heatable rain sensor. Alternatively, you can use it to set up a second line. An additional choke is required for this.

Source: eibabo®, Siemens 5WG11525-1AB22 KNX power supplyImage: Siemens 5WG11525-1AB22 KNX power supply

Can I monitor the utilization of a power supply?

If you want to check whether a power supply is reaching its limits in use, we recommend a device with an integrated diagnostic function. This allows device temperature, output current, output voltage, bus traffic and other current measured values to be sent via KNX. This enables troubleshooting or general monitoring.

What do I need a KNX emergency power supply for?

Whether you need a KNX emergency power supply depends on how high you assess the risk of a power failure and its consequences for your system. The emergency power supply is used to buffer the bus voltage. An external battery is connected to the device. This provides a voltage of 12V DC and ensures the bus voltage for some time. The integrated charging electronics of the KNX emergency power supply recharges the battery or maintains the state of charge. You can record the operating states (mains voltage, error warning, battery operation) using a binary input, for example. As a rule, KNX emergency power supplies are mounted on the DIN rail. Both the KNX emergency power supplies and the required batteries are available here in the eibabo® shop at reasonable prices.

What does PoE power supply mean?

The abbreviation PoE stands for 'Power over Ethernet'. This allows you to transmit the electrical power required for the operation of the individual participants via the data lines of the network cable. You do not need a separate power cable.

 


TIP:

With a PoE power supply, the effort involved in cabling wired Ethernet networks is reduced.


 

With this technology, the electrical voltage from the power supply is fed into the data cable. On the participant's side, this is diverted out again. To avoid interference, the participant should be PoE compatible. In this way, it can cleanly separate the incoming supply voltage from the data signal. If the end device is not PoE-compatible, the additional installation of a passive PoE splitter is necessary. The splitter takes the supply voltage from the data cable and feeds it via a separate line to the power input of the end device.

Can I get classic 12V and 24V power supplies for conventional applications from eibabo®?

Our classic power packs for the top-hat rail can be regulated depending on the model and are suitable for the power supply of external equipment. In addition, it is possible to use these for other equipment. Using a choke and a component for current limitation each, specific power supply units can also be used to supply one or more KNX lines. In addition to the installation technology, we offer you classic power supplies for universal use.

What power supplies and manufacturers would you recommend?

Basically, we recommend that you choose a device that suits your needs. Voltage supplies / power packs are standardized and are subject to legal requirements and regulations. If the technical parameters are completely identical, a price comparison between different manufacturers is of course worthwhile. In this catalog you will find KNX power supplies, KNX power supplies, KNX commissioning power supplies, KNX emergency power supplies, PoE power supplies, bus power supplies, IP power supplies PoE, battery modules for KNX power supplies, 12V power supplies and 24V power supplies for conventional applications. Rely on the excellent quality from the following leading manufacturers of smart home automation: ABB, Berker, Busch-Jaeger, EASYLUX, EIBMARKT, Gira, Hager, Issendorf, Jung, Lingg & Janke, MDT, Merten, Siemens, Somfy, Theben and Warema .

 

eibabo - technology store

 

Catalogue content:


In this eibabo® catalogue Installation bus systems > Power supply for bus system you will find items from the following product groups:

Item overview:

  • Audio electronics
  • Building system technology
  • Built-in power supply
  • Bus supply
  • Bus technology
  • Bus voltage supply
  • Care
  • Control transformer
  • DC power supply
  • DIN rails
  • Moellerfunk
  • Motion detector
  • Power supplies
  • Power supply
  • Power supply unit
  • Radio system
  • Safety power supply
  • Safety transformer
  • Switching power supply
  • System device
  • System power supply
  • System voltage


from the following manufacturers:

Manufacturer overview catalogue Power supply:

  • ABB
  • Busch Jaeger
  • Eaton
  • EIBMARKT
  • Elsner
  • Elso
  • ESYLUX
  • Gira
  • Hager
  • Issendorff
  • Jung
  • Legrand SEKO
  • Lingg & Janke
  • MDT
  • Mean Well
  • Merten
  • Peha
  • Schneider Electric
  • Siemens
  • Somfy
  • Theben
  • Wieland
  • Zumtobel


 
Find out here how to supply your KNX bus system with power. What power requirements do the individual KNX participants have? Which items do we recommend? This eibabo catalog contains power... read more »
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Power supply – energy for your KNX network

Find out here how to supply your KNX bus system with power. What power requirements do the individual KNX participants have? Which items do we recommend? This eibabo catalog contains power supplies and system devices for various automation systems, such as LCN, radio bus, KNX and many other systems.

How do I determine the right KNX power supply for my installation?

The most common power supplies in this catalog are for the KNX bus system. To determine the required power supply, you should first look at the structure of a KNX network. A distinction is made here between segments that are divided into a specific hierarchy. Imagine a tree whose trunk splits into branches. Twigs come off the branches. The branches represent the smallest 'unit' and are referred to as lines in the KNX network. Each line consists of the power supply, a KNX bus line and the participants. A main line would be the branch that connects multiple lines into an area. The area line represents the trunk that connects multiple areas. This structure makes sense for larger networks or if a division into several segments is recommended due to the structural conditions of a building.

In addition to the power supply for the participants, the bus itself also requires a power supply of 24V nominal voltage. This is transmitted along with the data signals on the bus line. Depending on the manufacturer, the corresponding power supplies deliver 28V to 31V slightly more than the nominal voltage. This creates a buffer, for example for possible line losses. KNX bus participants still work stably up to 21V. The voltage difference is used to compensate for voltage drops in the bus line or at the contact resistances. A line can theoretically include up to 64 devices and provides a maximum current of 640mA at a voltage of 28V to 31V. This statement is based on the assumption that each KNX participant is allowed a maximum of 10mA from the bus voltage. The load capacity of the strongest power supply of 640mA continuous current must not be exceeded.

Please plan in reserve

When dimensioning your lines, allow at least 15% buffer for later extensions. A 640mA power supply therefore corresponds to around 54 devices.


Smaller KNX power supplies are also available for fewer participants per line. If you know in advance that a line will never have more than a maximum of 32 subscribers (27 with buffer), you can choose a 320mA power supply. The same applies to a line with a maximum of 16 devices (14 with buffer). A 160mA power supply is sufficient here. In addition, there are larger 29V-30V power supplies with current limiters 640mA and KNX chokes separately. A KNX power supply always contains a KNX choke.

The power requirement of a KNX participant is usually standardized. This should not normally exceed 200mW. 150mW for power supply of the microprocessor and 50mW for the bus terminal. There are many KNX devices that do not require this power reference. There are also KNX participants with higher requirements, for example KNX actuators, KNX room controllers or KNX displays. Please take this into account when sizing your lines. Pay attention to possible voltage drops, because the devices do not draw a certain current from the bus, but a certain power. If the maximum current is expected to be exceeded, you should integrate fewer than 64 participants in this line.

How does the KNX power supply work?

In the KNX power supply, the power supply always provides direct current (DC) at the output. The difference between the designation transformer and power supply is essentially that a classic transformer always outputs alternating current (AC) and also only works with alternating current at the input. Depending on the manufacturer, the power supplies generate a supply voltage of 28V to 31V. When the bus is idle, the supply voltage of the power pack is present. This state corresponds to a logical '1'. The logical '0' is generated by an alternating voltage. In order to send the '0', the sending KNX device reduces the voltage by around 5V for a short time. This results in an immediate compensating impulse, which comes from a choke integrated in the power pack. The KNX line is thus decoupled from the associated KNX power supply by the choke. This prevents short circuits in the data telegrams caused by the power pack. The voltage change is necessary so that the recipient can use the information

Are there KNX power supplies for more than 64 participants per line?

In the eibabo® technology store you will find KNX power supplies up to 1280mA. However, it is not possible to set up a line with 128 participants. The power is distributed at two different outputs. There is thus the classic choked output with 640mA for the KNX bus as well as another unchoked output. Participants can be supplied with an auxiliary voltage via this output, for example a heatable rain sensor. Alternatively, you can use it to set up a second line. An additional choke is required for this.

Source: eibabo®, Siemens 5WG11525-1AB22 KNX power supplyImage: Siemens 5WG11525-1AB22 KNX power supply

Can I monitor the utilization of a power supply?

If you want to check whether a power supply is reaching its limits in use, we recommend a device with an integrated diagnostic function. This allows device temperature, output current, output voltage, bus traffic and other current measured values to be sent via KNX. This enables troubleshooting or general monitoring.

What do I need a KNX emergency power supply for?

Whether you need a KNX emergency power supply depends on how high you assess the risk of a power failure and its consequences for your system. The emergency power supply is used to buffer the bus voltage. An external battery is connected to the device. This provides a voltage of 12V DC and ensures the bus voltage for some time. The integrated charging electronics of the KNX emergency power supply recharges the battery or maintains the state of charge. You can record the operating states (mains voltage, error warning, battery operation) using a binary input, for example. As a rule, KNX emergency power supplies are mounted on the DIN rail. Both the KNX emergency power supplies and the required batteries are available here in the eibabo® shop at reasonable prices.

What does PoE power supply mean?

The abbreviation PoE stands for 'Power over Ethernet'. This allows you to transmit the electrical power required for the operation of the individual participants via the data lines of the network cable. You do not need a separate power cable.

 


TIP:

With a PoE power supply, the effort involved in cabling wired Ethernet networks is reduced.


 

With this technology, the electrical voltage from the power supply is fed into the data cable. On the participant's side, this is diverted out again. To avoid interference, the participant should be PoE compatible. In this way, it can cleanly separate the incoming supply voltage from the data signal. If the end device is not PoE-compatible, the additional installation of a passive PoE splitter is necessary. The splitter takes the supply voltage from the data cable and feeds it via a separate line to the power input of the end device.

Can I get classic 12V and 24V power supplies for conventional applications from eibabo®?

Our classic power packs for the top-hat rail can be regulated depending on the model and are suitable for the power supply of external equipment. In addition, it is possible to use these for other equipment. Using a choke and a component for current limitation each, specific power supply units can also be used to supply one or more KNX lines. In addition to the installation technology, we offer you classic power supplies for universal use.

What power supplies and manufacturers would you recommend?

Basically, we recommend that you choose a device that suits your needs. Voltage supplies / power packs are standardized and are subject to legal requirements and regulations. If the technical parameters are completely identical, a price comparison between different manufacturers is of course worthwhile. In this catalog you will find KNX power supplies, KNX power supplies, KNX commissioning power supplies, KNX emergency power supplies, PoE power supplies, bus power supplies, IP power supplies PoE, battery modules for KNX power supplies, 12V power supplies and 24V power supplies for conventional applications. Rely on the excellent quality from the following leading manufacturers of smart home automation: ABB, Berker, Busch-Jaeger, EASYLUX, EIBMARKT, Gira, Hager, Issendorf, Jung, Lingg & Janke, MDT, Merten, Siemens, Somfy, Theben and Warema .

 

eibabo - technology store

 

Catalogue content:


In this eibabo® catalogue Installation bus systems > Power supply for bus system you will find items from the following product groups:

Item overview:

  • Audio electronics
  • Building system technology
  • Built-in power supply
  • Bus supply
  • Bus technology
  • Bus voltage supply
  • Care
  • Control transformer
  • DC power supply
  • DIN rails
  • Moellerfunk
  • Motion detector
  • Power supplies
  • Power supply
  • Power supply unit
  • Radio system
  • Safety power supply
  • Safety transformer
  • Switching power supply
  • System device
  • System power supply
  • System voltage


from the following manufacturers:

Manufacturer overview catalogue Power supply:

  • ABB
  • Busch Jaeger
  • Eaton
  • EIBMARKT
  • Elsner
  • Elso
  • ESYLUX
  • Gira
  • Hager
  • Issendorff
  • Jung
  • Legrand SEKO
  • Lingg & Janke
  • MDT
  • Mean Well
  • Merten
  • Peha
  • Schneider Electric
  • Siemens
  • Somfy
  • Theben
  • Wieland
  • Zumtobel
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