Installation and Operations Guide
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General installation guidelines
© Honeywell LTBT-TM-AZWIOG Rev. 0001BETA
9
MS/TP LAN wiring
The AZW-5000 coordinator device communicates with the BACnet system over
the MS/TP LAN, which uses the EIA–485 signaling standard. Transceivers
communicate with their associated unitary controllers over
Note This section applies only to the coordinator device.
Terminating MS/TP LAN cabling
MS/TP terminations are located at the top of the AZW-5000. See Fig. 4 on p. 15.
Maintain polarity of the MS/TP wire run throughout the MS/TP LAN.
Note Basic information about MS/TP terminations at the AZW-5000 are
provided here. See the BACtalk System Design Guide (LTBT-TM-SYSDSGN)
for more detailed information and limitations with respect to MS/TP LANs —
distance requirements, unit loads, repeater architectures, and so on.
Table 2 MS/TP LAN facts
Transmission speed 9.6, 19.2, 38.4, 76.8Kbps (figured at global controller).
At startup, AZW-5000 devices operate at 76.8 Kbps.
Layout Bus.
Cabling BACnet specifies the following. Shielded, twisted-pair
cabling with characteristic impedance between 100 and
130 Ohms. Distributed capacitance between conductors
must be less than 30 pF/foot (100 pF/m). Distributed
capacitance between conductor and shield must be less
than 60 pF/foot (200 pF/m). Foil or braided shield
acceptable.
Segment length Segments between transceivers and controllers/devices
should be kept as short as practical to reduce cable
costs. Longer segments are acceptable to improve radio
signal strength.
The segment between a coordinator and its associated
BCM can be up to 4000 ft. (1071 m.), but will typically
be much shorter.
Maximum devices
overall
One coordinator and 15 transceivers/Repeaters.
Maximum devices
per segment
One transceiver and one controller per subnet.
MS/TP repeaters Do not use.
Terminating
resistors
not applicable
Shield grounding Ground transceiver shield drain wires at single point
earth (panel) ground, not AZW-5000 ground. Tape off
the shield drain wire at the other end.
Grounding coordinator shield wires is not necessary
unless the coordinator is located more than ten feet
from its associated BCM.
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