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CNT-SVX05A-EN
Communications
Figure 4 — Trunk and branch configuration for communication link wiring
• Total wire length for all branches is limited to 1,600 ft (500 m). (Comm5 wire
length limitations can be extended through the use of a link repeater)
• The maximum number of branches is ten
• See the following section on
Termination resistance placement for Comm5
links
Termination resistance placement for Comm5 links
To correctly install a Comm5 link, termination resistors are required. For daisy
chain configurations, the termination resistance (measured in ohms) must be
100 ohms at each end. For trunk and branch configurations, the termination
resistance must be 50 ohms (use two termination resistors in parallel).
For correct termination placement, follow the guidelines below:
• Terminate the daisy chain configuration with a resistor at the extreme end of
each wire
• Terminate a trunk and branch configuration with a resistor or resistors placed
at one point on the link. The termination resistance for trunk and branch
configuration can be achieved by using two terminating resistors in parallel.
While it is not necessary that the termination resistance be placed at the
controller, it may be the most convenient
• When terminating a trunk and branch configuration, it is best to terminate at
the point where the branching occurs or at a point very close to it
• If the link contains more than one type of wire, the link will probably have to
be manually tuned. Trane recommends that only one type of wire be used for
the Comm5 communication link
• A set of as-built drawings or a map of the communication wire layout should
be made during installation. Any sketch of the communication layout should
feature the terminating resistor placement
