How are KNX Cables Installed?
There are two aspects to consider when it comes to wiring:
Physical Wiring and Installation Topology
KNX cable is mains rated and due to the arrangement of the internal cores, it can be run directly next to mains cabling. In fact, it is usually much easier to do so as it can be run at the same time by the site electrician.
When running around a building it can be installed as a daisy chain or star wired and it is possible to create a spur. The only restriction is a loop cannot be created at any point of the bus. It is advised to daisy chain from point to point as it makes fault finding and maintenance easier. It is also common to run the cable around the building or floor in a loop but only terminate one end. This provides a back up if the cable is damaged or if the line needs to be expanded. It is important to label the cable clearly if this method is used.
A KNX device can be a maximum of 350m from a power supply, which would normally be mounted in a distribution board and the maximum length of bus cable used in a single line is 1000m.
A single KNX line segment can have up to 64 devices, however a 10% allowance for future expansion is advised. Two line segments can be joined directly together but after this a hierarchy approach is needed with each line segment needing to link to a main line. This could be achieved by having a distribution board on each floor with a main line linking them together. Each board would then have another line running around the local devices. Alternatively, each line could go back to a central point where they would each link to the main line.
Wherever line segments are connected, a line coupler and power supply will be needed, which is why this is normally completed in a distribution board or enclosure.