{"id":5878,"date":"2026-10-14T10:41:00","date_gmt":"2026-10-14T07:41:00","guid":{"rendered":"https:\/\/www.etkkablo.com\/en\/?p=5878"},"modified":"2026-09-10T17:16:36","modified_gmt":"2026-09-10T14:16:36","slug":"knx-cable-specification","status":"publish","type":"post","link":"https:\/\/www.etkkablo.com\/en\/blog\/knx-cable-specification\/","title":{"rendered":"How to Specify KNX\/EIB Cable: Construction, Shielding and Applications"},"content":{"rendered":"\n

A KNX cable specification<\/strong> defines the electrical, mechanical and construction requirements of the twisted-pair bus cable used to connect devices in a KNX building automation<\/a> network. Although KNX bus cable may appear relatively simple compared with high-frequency Ethernet or instrumentation cables, its conductor size, pair geometry, twisting, shielding, resistance, capacitance and insulation performance directly affect reliable communication across the building.<\/p>\n\n\n\n

KNX systems can control lighting, heating, ventilation, air conditioning, blinds, shutters, access control, energy management and many other building functions through a shared communication bus. Consequently, the cable forms the physical communication backbone connecting sensors, switches, actuators, controllers and other KNX devices.<\/p>\n\n\n\n

The terms KNX cable<\/strong> and EIB cable<\/strong> are also frequently used together. EIB, or European Installation Bus, was one of the technologies that preceded KNX. EIB became a central technical foundation of the later KNX system, which is why EIB cable terminology remains common in European specifications, product names and legacy installations.<\/p>\n\n\n\n

However, not every green twisted-pair cable should automatically be considered suitable for KNX. A professional specification should evaluate conductor diameter, loop resistance, twisting, capacitance, inductance, screen construction, voltage withstand, fire performance and environmental requirements.<\/p>\n\n\n\n

Quick answer:<\/strong> A standard KNX TP cable typically uses two twisted copper pairs, commonly red\/black and white\/yellow, with the red\/black pair serving the KNX bus. Standardized KNX cable requirements specify conductor diameters from 0.8 to 1.0 mm, controlled electrical characteristics, pair twisting and an overall screen. The exact sheath system can then be selected according to the project, including PVC, halogen-free or outdoor constructions.<\/p>\n\n\n\n

KNX Cable Specification at a Glance<\/h2>\n\n\n\n
Parameter<\/th>Typical \/ Standardized KNX Requirement<\/th>Why It Matters<\/th><\/tr><\/thead>
Transmission medium<\/td>Twisted pair<\/td>Carries KNX communication and bus power<\/td><\/tr>
Number of pairs<\/td>Two pairs for standardized cable<\/td>Provides bus pair plus spare pair<\/td><\/tr>
Common conductor colours<\/td>Red\/black and white\/yellow<\/td>Consistent identification<\/td><\/tr>
Wire diameter<\/td>0.8\u20131.0 mm for standardized KNX cable<\/td>Controls resistance and voltage drop<\/td><\/tr>
Conductor material<\/td>Copper<\/td>Provides defined electrical performance<\/td><\/tr>
Twisting<\/td>Minimum defined twist requirement<\/td>Supports balanced communication and EMC performance<\/td><\/tr>
Screen<\/td>Overall screen<\/td>Reduces electromagnetic interference<\/td><\/tr>
Drain wire<\/td>Used with the screen<\/td>Provides screen continuity and termination<\/td><\/tr>
Loop resistance<\/td>Controlled<\/td>Affects voltage drop and network length<\/td><\/tr>
Capacitance<\/td>Controlled<\/td>Influences signal transmission<\/td><\/tr>
Inductance<\/td>Controlled<\/td>Part of the KNX transmission characteristics<\/td><\/tr>
Outer sheath<\/td>PVC, LSZH or special compound<\/td>Matches fire and environmental conditions<\/td><\/tr>
Network cable length<\/td>Up to 1000 m per standard cable segment under applicable KNX rules<\/td>Important for system topology<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Therefore, KNX cable selection should not depend only on conductor count or cable colour. Electrical transmission properties and compliance with the applicable KNX requirements are equally important.<\/p>\n\n\n\n

What Is KNX?<\/h2>\n\n\n\n

KNX is an open building automation standard that allows equipment from different manufacturers to communicate within one interoperable control system.<\/p>\n\n\n\n

Typical KNX applications include:<\/p>\n\n\n\n