Trane LPC Install And Operation Instructions page 45

• Total wire length for all branches is
limited to 1,600 ft. Comm5 wire length
limitations can be extended through the
use of a link repeater.
• The maximum number of branches
is 10.
• 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. See Figure I-IP-6.
LPC-SVX01C-EN
Installation
Figure I-IP-7 . Trunk and Branch Configuration for Communication Link Wiring
Figure I-IPR-8. Daisy Chain Resistor Placement
Recommended Wiring
Practices
The following guidelines should be
followed while installing communication
wire.
• Comm5 is not polarity sensitive. Trane
recommends that the installer keep
polarity consistent throughout the site.
• Only strip away two-inches maximum
of the outer conductor of shielded cable.
• Make sure that the 24VAC power
supplies are consistent in how they are
grounded. Avoid sharing 24VAC
between Comm5 UCMs.
pre-startup
requirements
• Avoid over-tightening cable ties and
other forms of cable wraps. A tight tie
or wrap could damage the wires
inside the cable.
• Do not run Comm5 cable alongside or
in the same conduit as 24VAC power.
• In an open plenum, avoid lighting
ballasts, especially those using 277VAC.
• Do not use a trunk and branch
configuration, if possible. Trunk and
branch configurations shorten the
distance cable can be run.
45