A KNX line coupler is required in a KNX installation when you need to connect different KNX lines or segment a KNX installation into multiple lines for better scalability, performance, and signal integrity.
You need a KNX Line Coupler in the following situations:
1. When a line exceeds the device limit:
Each KNX TP (twisted pair) line can support up to 64 devices.
If you need more than 64 devices, you split the installation into multiple lines, and each line is connected to the main line (or backbone) via a line coupler.
2. To isolate traffic between lines:
A line coupler filters telegrams, reducing the amount of KNX bus traffic on each line.
Only necessary telegrams (e.g., group addresses flagged for routing) pass through the coupler.
This improves performance and reliability, especially in large projects.
3. For better voltage and signal management:
Each KNX line must have its own power supply with choke.
Couplers electrically isolate the power supplies of each line while still allowing data communication between them.
4. When connecting a line to a backbone (area line):
In larger installations with multiple areas, each area has a main line (area line), and lines within each area connect to it via line couplers.
Similarly, backbone couplers connect area lines to the backbone.
Summary Table:
Scenario Device Required?
>64 devices on a single line Line Coupler ✅
Multiple building sections or floors Line Coupler ✅
High bus traffic management Line Coupler ✅
Single-line installation (<64 devices) Line Coupler ❌
