How many 5104BCL in one network?

Discussion in 'General Discussion' started by 2SC, Jan 21, 2009.

  1. 2SC

    2SC

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    I searched but I didn't find anything about.

    Is there any limitation on the number of the 5104BCL that are installed in a C-Bus network?
     
    2SC, Jan 21, 2009
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  2. 2SC

    Newman

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    The same rules apply for the Bus Coupler as they do for regular 2000 series key units - a combined total of 100 units.
     
    Newman, Jan 21, 2009
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  3. 2SC

    NickD Moderator

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    A bus coupler is an "18mA" C-Bus input unit... like a standard key unit, so you can theoretically have up to 100 of them on your network (although in that case you couldn't have anything else).

    The other (and probably more practical) limitation on bus couplers is the length of cable you can use to connect to the external switches... you are limited to *a total of 10m* of cable to external switches on bus coupler *per network*.

    ie you can have one bus coupler with 10m of cabling to switches, or 10 bus couplers with 1m each.. etc..

    Note also that if you have a 4 channel bus coupler with 1m of cable on each switch... this counts as 4m...

    Nick
     
    NickD, Jan 21, 2009
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  4. 2SC

    2SC

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    Nick,
    since the bus coupler is actually a set of dry contacts, I can understand a limitation to the length of cable connecting external switches on bus coupler.
    Why this limitation of *a total of 10m per network* ?
     
    2SC, Jan 22, 2009
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  5. 2SC

    ______.

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    I've never heard that limitaion in all the time i've been working with bus couplers :confused:
    I'm with 2sc i understand a limitaion per coupler but why per network :confused:
    I know i've used more the 10m of cable from couplers to dry switches without any problems.
     
    ______., Jan 22, 2009
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  6. 2SC

    Newman

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    The total cable length issue is one of network balance. Each wire you run out to a dry contact switch from a Bus Coupler is effectively connected to the C-Bus common connection. The switch input cables introduce a small amount of capacitive coupling to the surrounding environment. This introduces a capacitive imbalance to the C-Bus network. The more cable you add, the more unbalanced the network becomes. The more unbalanced the network becomes, the more susceptible to electrical noise the network becomes and, as a result, the less reliable communication becomes.

    Page 6 of the 5104BCL Installation Instructions describes this 10m limit.

    I *think* they still teach the 10m per network in the C-Bus training courses. In a practical application there are lots of variables for how much coupling will occur to the surrounding environment such as the wall construction, the type of cable used, the type of switch, surrounding equipment, etc.

    As you have experienced, there is some leeway, however when your job site is misbehaving, the length of any wiring connected to bus couplers may be one of the questions that gets asked.

    The Aux Input unit addresses both the cable length and the network imbalance issues inherent in a bus coupler, but as a consequence it is a physically larger product.
     
    Last edited by a moderator: Jan 22, 2009
    Newman, Jan 22, 2009
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