Maximum line length
No more than 1000 metres per line
- Total length of all segments ≤ 1000 m
- Distance between two devices ≤ 700 m
- Distance from power supply to device ≤ 350 m
← All knowledge guidesKNX/EIB Standard
KNX Cable Installation Requirements
Professional guide to KNX/EIB bus cable routing and installation. Technical requirements, standards and best practices for reliable building automation.
Core installation requirements
Following these requirements ensures reliable and long-lasting operation of your KNX system.
Electrical isolation
Separation from power cables
- Minimum 4 mm from 230V power cables
- Use separate cable ducts
- Crossings only at 90° angle
EMC protection
Shielding and grounding
- Ground cable shield on one side only
- Avoid parallel routing with power lines
- Use certified KNX cable
Operating conditions
Temperature and humidity
- Operating temperature: -5°C to +45°C
- Humidity: up to 93% non-condensing
- IP20 protection for indoor installation
Prohibited
- Do not route KNX cable in the same duct as power cables
- Do not use ordinary twisted-pair cable instead of certified KNX cable
- Ring topologies within a line are strictly forbidden
Best practices
- Use colour coding: red (+), black (−)
- Leave cable slack in junction boxes
- Document all connections and topology
- Check polarity before connecting devices
Technical specifications
Detailed cable characteristics and KNX/EIB system parameters.
Cable types
YCYM 2x2x0.8
Primary cable for indoor installation
- Cores2 × 2 × 0.8 mm
- Outer diameter5.0 mm
- Resistance≤ 73 Ω/km
- Insulation voltage300 / 500 V
- ShieldNone
J-Y(St)Y 2x2x0.8
For installation in high-interference environments
- Cores2 × 2 × 0.8 mm
- Outer diameter6.0 mm
- Resistance≤ 73 Ω/km
- Insulation voltage300 / 500 V
- ShieldAluminium foil
Topology limits
| Devices per line | 64 | pcs |
| Lines per area | 15 | pcs |
| Areas in system | 15 | pcs |
| Devices in system | 57 600 | max |
Electrical parameters
| Bus voltage | 29V DC | 21–32V |
| Current consumption | 10 mA | typical |
| Data rate | 9600 | bit/s |
| Access method | CSMA/CA | — |
Wire colour coding
Red+UB (positive)
Black−UB (negative)
YellowReserve / SELV
WhiteReserve / SELV
Supported topologies
KNX supports free topology without closed loops.
Line
Devices connected in series
Advantages
- Simple installation
- Minimal cable use
Disadvantages
- Break affects entire line
Star
All devices connected to a central point
Advantages
- Device independence
- Easy diagnostics
Disadvantages
- More cable required
Tree
Combination of line and star topology
Advantages
- Flexibility
- Optimal cable use
Disadvantages
- More complex planning
Important: ring topology is prohibited
Ring connections (closed loops) are strictly forbidden in KNX. They cause telegram collisions and system failures. Always verify the absence of closed loops before commissioning.
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