Viconics VTR7300 BACnet Integration Manual - Manual (Page 27)

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End Of Line (EOL) Resistors
MS/TP network must be properly terminated. For daisy chain configurations, you must install an EOL
resistor at each end of the daisy chain. Depending on your MSTP network configuration, the resistance
value of the EOL resistor may change:
 Viconics’ devices are installed at both ends of the MSTP network:
120 Ohms resistor should be installed at each end.

A Viconics device is installed at one end of the MSTP network and a 3
rd
party device is
installed at the other end:
Install an End-Of-Line resistor value that matches the 3rd party devices instructions regarding its
EOL resistor value;

3
rd
party devices are installed at both ends of the MSTP network:
Follow the 3rd party devices instructions regarding its EOL resistor value.
Network Adapter
The polarity of the connection to the cable is important. From one module to the other it is important that
the same colored wire be connected to “plus” or “+” and the other colored wire be connected to the “minus”
or ”-“. Figures 7 shows the proper MS/TP connections and the location of the Status LED. This Status LED
may help to troubleshoot network problems.
Figure 7: Correct MS/TP connections and location of a Status LED on a BACnet
module
IMPORTANT NOTE: The Ref terminal should NEVER be used to wire shields. The 2 shields from each
feed of the network connection to a thermostat should be wired together in the back of the thermostat and
properly protected to prevent any accidental connection to the ground.
The joined shield connection should then be grounded at a SINGLE point on the whole segment. More than
one ground connection to a shielded wire may induce ground loop noises and affect communication.