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4A) 3
rd
Party BACnet Integration
BACnet being an open protocol also means that the Viconics zoning system products can be seamlessly
integrated into any 3
rd
party BACnet supervision system.
This enables the whole system to be integrated into an open building automation DDC system. From there
options are endless for advanced added functionality: Full graphic interface of RTU units and ZONE zones,
trends, charts and logs, automatic responses to alarms, advanced energy management, Etc……
Information on 3
rd
party BACnet integration is available on document
ITG-VZ7xxx-BAC-Exx.
4B) Communication Wiring and Layout
Wire:
Viconics recommends the use of balanced 22-24 AWG twisted pair with a characteristic impedance
of 100-130 ohms, capacitance of 17 pF/ft or lower, with a braided shield.
Layout:
RS485 networks use a daisy chain configuration. A daisy chain means that there is only one main
cable and every network device is connected directly along its path.
Other methods of wiring an RS485 network may give unreliable or unpredictable results. There are no
troubleshooting methods for these types of networks. Therefore, a great deal of site experimentation may
have to be done, making this a difficult task with no guarantee of success. Viconics will only support daisy
chain configurations. The following illustrates two improper network configurations and the proper daisy
chain configuration.
Figure 3: Three different network configurations: star, bus, and daisy chain. Only the
daisy chain configuration is correct for an EIA-485 network.
A daisy-chain wiring scheme does not allow for T connections. I.E. the network wire needs to be wired
down to each controller communication terminals before going to the next device. No junctions of any kind
are recommended to be installed. Except for the first and the last devices on the network, all controllers
should have 4 wires connected to the + and – network connection.
-
The + connection should have a wire going to the previous device and a wire going to the next device
-
The - connection should have a wire going to the previous device and a wire going to the next device
The best layout for the communication network is the one that will result in the shortest possible network
wire length. The allowed maximum network wire length is 1200 meters (4000 feet). It is not necessary to
have the wire follow each controller MAC address in sequence. The wire can be connected from one
device to the next closest without any specific preset architecture. The same applies to the RTU controller;
it can be physically located anywhere on the network and is not required to be at the beginning or at the
end of the communication wire.
Polarity:
The polarity of the network connections to the cable is important and needs to be respected.
From one controller network connection to the other it is important that the same coloured wire be
connected to “plus” or “+” and the other coloured wire be connected to the “minus” or”-“.
