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Best topology for KNX home installation

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    Best topology for KNX home installation

    Hello,

    For the temporary installation during construction a simple topology was used for minimal functions and to evaluate and test products (for example checking real world coverage for presence detectors):
    - 0.x.x - IP backbone
    - 1.1.x - TP line, with IP router on 1.1.0

    Property is two story home, with a separate physical KNX line wired for each story and additional KNX wires for outside. There are around 80 KNX devices planned, which include presence detector for each room or distinct area in open space, wall and bed-side switches for control where presence alone cannot be used, Jung LS Touch devices in most important rooms as thermostats and control of minor functions, underfloor heating and air conditioning units integrated into KNX.

    However above topology might not be well suited for actual installation because:
    1) total calculated current for all KNX devices is ~1200mA (under 600mA per floor plus little bit for outside and distribution ), which is awfully close to 1280mA capability of the larger power supplies and would prevent expanding the installation with new devices in future without changing topology;
    2) there are few motion/presence detectors and switches, and in future weather station and automated flag pole outside; it would be best to isolate those on a separate line for security.


    Option 1
    - 0.x.x - IP backbone
    - 1.0.x - TP main line with devices in distribution and Floor 1 or 2
    - 1.1.x - TP line with devices for second floor, with bus coupler to main line
    - 1.2.x - TP line with outside devices, with bus coupler to main line
    This would require 3 KNX power supplies, 1 IP router, 2 TP bus couplers, and each of the TP lines would leave plenty of room to expand if switching to 1280mA power supplies

    Option 2
    - 0.x.x - IP backbone
    - 1.0.x - TP main line with all indoor devices on it, with 1280mA power supply, which would be sufficient initially
    - 1.1.x - TP line for outdoor devices with bus coupler to main line
    This would require one less power supply and TP coupler initially, but could the main line be expanded in future if 1280mA current has to be exceeded without reorganizing physical addresses? KNX documentation states that a single line (1.0.x in this case) can be split into multiple segments, each with it's own power supply and TP repeater (essentially a TP coupler without filter table and coupling same physical address ranges on both sides), however I have never seen or tried such deployment in practice.

    There is of course Option 3 - IP backbone with 3 IP routers and 3 TP main lines, but TP couplers are much cheaper than IP routers, so this makes no sense.

    Which of the options do you think is the best, or maybe there is a better way?

    Thanks,
    Jekabs

    #2
    As long as you have enough separate KNX cables, everything in topology can be changed later with less effort.

    So I recommend option 2.
    ----------------------------------------------------------------------------------
    "Der Hauptgrund für Stress ist der tägliche Kontakt mit Idioten."
    Albert Einstein

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      #3
      Zitat von gbglace Beitrag anzeigen
      As long as you have enough separate KNX cables, everything in topology can be changed later with less effort.

      So I recommend option 2.
      Yes, there are separate physical cables for each floor, garage/storage/boiler room, attic, outdoor areas, terrace and balcony. So the wiring allows any kind of topology by connecting TP wires in the distributor in the desired configuration.

      Kommentar


        #4
        I chose option two for my house as well. This option is sufficient in most cases for a single-family home and can be easily expanded later. As you correctly mentioned, option 3 is already ruled out due to cost reasons. With this option, you would also be dependent on the network.

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          #5
          Option 2 here (with an additional KNX RF line 1.2.x). If you get a power supply for the main line with diagnostics you can watch the current the line needs. For 80 devices I doubt you would even get close to the 1280 mA. With about 80 devices in our setup the supply shows a maximum current (so only during the startup phase of the bus) of just below 900 mA and a mean of about 600 mA. Of course those numbers highly depend on the actual devices you use, but with quite a bunch of displays (MDT GT II Smart) and even a few of Steinel's sensors (those need the most current by quite some margin) I don't think our setup is on the low end.
          Chris

          Kommentar


            #6
            Few power hungry devices ia the main reason I was worried - 6x new Jung LS Touch displays at 60mA each and few Steinel sensors as well...

            Which of the 1280mA supplies with diagnostic would you recommend? Enertex Dual Power supply looks interesting with capability to power both main indoor line and secondary outdoor and also third unchoked output for IP router power. Looks like a product designed exactly for a single family home.

            Kommentar


              #7
              Personally I would not go with a supply that covers more than one line. The PS is the single point of failure in a KNX setup, so I would not want it to be potentially harmed by whatever happens on the outside. I use an MDT STC 1280 and happy with that, but there's most likely other options out there too.
              Chris

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