Cable and Installation
Standard cable: J-Y(St)Y 2×2×0.8 mm² or YCYM 2×2×0.8. The red-black wire pair carries bus voltage and data. The green-white pair is a spare and can be used for special functions.
KNX cable may be installed together with 230 V conductors in the same conduit if SELV requirements are met (EN 50174-2). No minimum separation is required, but separate conduits are recommended for maintenance and EMC.
Limits and Cable Lengths
Line, star and tree topologies are permitted, no ring. Stub connections (drops) are allowed. Maximum total cable length per line: 1,000 m; maximum distance between two devices: 700 m; maximum distance between a device and the power supply: 350 m.
For larger installations with long runs and many devices, a current budget calculation is recommended: the sum of current draw from all devices (from datasheets) must remain below the rated capacity of the power supply.
Key Facts
- Cable: J-Y(St)Y 2×2×0.8 mm² (standard)
- Max. total length per line: 1,000 m
- Max. distance between two devices: 700 m
- Max. distance device–power supply: 350 m
- No ring, line, star, tree allowed
- Bus voltage: 29 V DC SELV (25–31 V permissible)