KNX Cable & Connector Guide 2025

KNX is the World’s most popular open-standard for building automation.

Multi-vendor support drives tough standards for cabling & connectivity to ensure:

In a KNX installation, the use of non-certified cabling is one of the leading causes of bus failure, telegram loss, and installation problems.

High-quality KNX bus cabling is essential to reliability.

■ KNX TP1 Bus Cable — Structure, Colors, Shielding & Technical Specs

TP1 (Twisted Pair 1) is the standard cable for KNX installations. Its core build and conductor colors are standardized for easy integration.

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KNX Cable Structure

Standard KNX TP1 cabling includes:

• Solid copper conductor (Standard Ø 0.8mm)

• 1 or 2 twisted pairs

• Aluminum foil screen and drain wire

• Standard green RAL 6018 outer sheath for easy identification in the field

Standard KNX wire colors:

• Red = Bus + (positive)

• Black = Bus – (negative)

• Yellow / White = Auxiliary / Reserve pair

Standard colors reduce installation mistakes, particularly when tracking down problems.

EMC Considerations — Shielding, Drain Wires & Noise Immunity

Today’s buildings and electrical environments are more electrically noisy (LED power supplies, inverters, and HVAC units).

To ensure KNX performance:

Shielding & Grounding (Drain-Wire Rules)

• Ensure the shield implies no ground loops. If grounding is required by the topology, connect the drain wire at one end only (typically the distribution board end).

• Double grounding creates ground loops and injects electromagnetic noise into the KNX bus.

• Maintain cable twists as close to the terminals as possible to preserve noise immunity.

Cable Routing Best Practices

• Avoid long parallel runs with 230/400V power and dimmer lines.

• Cross power runs at 90° where necessary.

• Use shielded TP1 cables in high EMC areas.

■ Professional Installation Rules

IEC Standard Cable Separation Distances (IEC 60364)

To improve KNX installation safety & minimize disturbances:

• Hold a minimum of 4mm distance to 230/400V power cables

• Or use segregated trunking with insulating barriers

• Avoid running KNX cables around switching loads (e.g., motors)

Always follow separation distances for long-term reliability.

Installer Mistakes To Avoid

■ KNX Connectors — Types, Advantages, Colors & Applications

KNX connectors are standardized to guarantee compatibility with third-party manufacturers.

Type 5.1 Connector — Common KNX Terminal (WAGO 243 Design)

Commonly found in:

• Switches

• Motion Detectors (PIR)

• Actuators

• Binary inputs

• Thermostats & Temperature Sensors

Technical Specifications

• 2 pins and a spring clamp. No screw locking

• Accommodates solid wires of 0.6mm to 0.8mm

• Permits 2 or more wires to attach

• Multi-meter ready: Embedded testing slots allow for voltage checks without removing wires

Standard color orientation:

• Red = Bus + (positive)

• Black = Bus – (negative)

• Yellow/White = Auxiliary/Reserve pair

Installer Tip

• The housing color often indicates the function for fast recognition:

  Dark Grey Shell → Bus pair (Red and Black)

  Light Grey Shell → Auxiliary pair (Yellow and White)

• Ensure wires are fully inserted to guarantee reliable contact.

Type 7.1 Connector — Plug/Socket For In-The-Field Wiring

Used for structured cabling:

• Ceiling voids

• Raised floor spaces

• Modular Architecture

Features:

• Quick installation & removal

• Mechanical latch

• Durable for in-field installation

Type 7.2 Connector — KNX + Mains Connector

Used for integrated devices having:

• 230 Volts mains supply

• KNX communication

Features:

• Double insulation of circuits

• Individually optimized creepage/clearance

• Combined LV + SELV routing

Commonly found in:

• Lighting appliances

• Modular integrated electrical devices

RJ45 (Type 8.1) — Special Use Only

• Not used for KNX TP1 bus communication.

• Primary Uses:

• KNX IP Interface & IP Routing (Backbone)

• In-the-field diagnostics / PC connection

■ Certification — Why the KNX Logo Matters

The sale of ‘KNX’ products is dotted with labels and names like:

• ‘KNX Compatible’ or ‘KNX-style cable’

• ‘Suitable for KNX’

A KNX Logo means full certification and assurances of:

KNX Logo = Advanced Assurance for Specifiers and Integrators

■ Future Trends (2025 & Beyond)

KNX Secure & Cable Performance

KNX Secure requirements (prevention of replay attacks, sabotage, and eavesdropping) increase the demand for high-integrity cabling.

High-performance TP1 cabling is the physical foundation for KNX Secure networks.

CPR Performance Characteristics (Europe)

In the EU, building wire and cable products need Construction Product Regulation (CPR). Possible classifications include:

• Class Eca – for basic residential usage

• Class Dca – for medium fire risk environments

• Class Cca – for strict safety commercial applications

Increasing Class levels apply for:

• Schools

• Hospitality buildings

• Public Use Buildings

• Transport Hubs/Stations, etc.

For the European market, standard CPR classification applies.

■ Choosing the Right KNX Cable & Connector – Application Matrix

Seeking Certification For Manufacturers:

• Keep to KNX Connector and electrical specs

• Provide documentation as KNX Safety Standard

■ Conclusion

Your KNX Installation depends upon robust cabling and connections:

• Certified KNX cabling

• Standard Conductor colors

• Further drain wire & earthing rules

• IEC separation distance guidelines

• Integrated, compatible connectors, ensure:

High-Quality KNX cabling isn’t optional for reliable Automation.

Contact us for more information

michael@zion-communication.com

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