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KNX line limits

I want to ask general question to more experienced KNX users/installers. As we know KNX line's communication speed is very slow for now, but topology allows many devices to be installed....

I will have aprox. 20-30 devices on 12 lines (looks not so many but..), all of them will be connected over couplers with one main Schneider SL for visualization.. Now I begin think about logic programming and device configuring - from sensors I can receive MANY datas - I have so named multi-sensors.. Not all will works just in own segment...

Modern solution to use IP couplers to main line... But where are the limits?? In project design was used standard but modern (with security) KNX line couplers...

How find balance in working speed and not overload KNX lines? Can you please share your experience in this question?

Thank you in advance,

Hi Alexander.

We never use TP couplers.

If you always use IP couplers instead trafic isn't a problem.

The answer is quite simple, a KNX TP bus can handle aprox 40 telegrams a second, if you have moments where you have more then the max (this occurs most logical on the backbone) you need to switch to IP couplers.

There are a lot of devices that will increase traffic like motion sensors, thermostats and all other sensors that produce telegrams on cyclic base or motion inputs. When having only switching actuators with manual inputs you probably have a very low traffic, but adding more intelligent devices will increase traffic.

My rule of thumb is 1 to 3 lines can be done without filtering, 4 to 8 can be done with some filters (if you don't need all status infor into the visu) and any above the 8 lines must be IP. If your visu needs all info then you need an IP backbone when having more then 2-3 lines.

thank you very much for information, in future will use only IP couplers. Devices now more and more smart, it will of course increase traffic.


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