IM 781-2 Page 23
A stub is a piece of cable that is wired between the node and the bus (see Figure 17). Note that if the bus is wired
directly to the node, there is no stub, and thus the stub length is zero. If you are wiring to a field terminal strip on a
unit, be sure to account for any factory wiring between the terminal strip and the controller. This wiring is considered
part of the stub.
4. Two terminations are required in each segment. One must be located at each end of the bus.
Network Cable Termination
The network integrator determines which network topology is appropriate for a particular installation. For simple networks
with a few devices on the network, the free topology is often adequate. The terminators are selected to match the network
topology. At the time of this writing, the recommended terminator for a single termination, free topology network is the
Echelon Model 44100 Terminator, and for double termination bus topology networks, two Model 44101 Terminators are
recommended.
Qualified Cables
At the time of this writing, Echelon has qualified three twisted-pair network communications cables that are available,
shielded or unshielded, from a large number of different sources. Some local codes or applications may require the use of
plenum rated cable. The following meet these cable specifications.
1) TIA568A Category 5 cable (24AWG/0.51mm)
2) NEMA Level IV cable (22AWG/0.65mm)
3)
Generic 16AWG (1.3mm) (similar to Belden 85102)
!
CAUTION
• Do not install the cable in the same conduit with power wiring.
•
The temperature of the cable must not exceed 131°F (55°C).
Note: Ideally, one continuous piece of cable should connect any two controllers. This reduces the risk of communications
errors. If the cable must be spliced, use crimp-type butt connectors (better) or solder (best). Do not use wire nuts.
AnaIog/Digital Inputs and Outputs Wiring
All inputs and outputs on the CSM are optional except the Chilled Water Supply Temperature sensor. The requirement of
all other sensors is dependent on the CSM features necessary. See Table 4 for details about sensor requirements.
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