Submittal Sheet

FOR FAN COIL/HEAT PUMP/CONVENTIONAL SYSTEMS
3 31-00096—02
MS/TP network. Each BACnet FF device uses a high-
quality EIA-485 transceiver and exerts 1/4 unit load on the
MS/TP network.
Cabling should be selected that meets or exceeds the
BACnet Standard which specifies the following: an MS/TP
EIA-485 network shall use shielded, twisted-pair cable with
characteristic impedance between 100 and 130 ohms.
Distributed capacitance between conductors shall be less
than 100 pF per meter (30 pF per foot). Distributed
capacitance between conductors and shield shall be less
that 200 pF per meter (60 pF per foot). Foil or braided
shields are acceptable. The Honeywell tested and
recommended MS/TP cable is Honeywell Cable 3322 (18
AWG, 1-Pair, Shielded, Low Cap, Plenum cable),
alternatively Honeywell Cable 3251 (22 AWG, 1-Pair,
Shielded, Plenum cable) is available and meets the BACnet
Standard requirements (www.honeywellcable.com).
The BACnet MS/TP network is polarity sensitive. The
maximum BACnet MS/TP network Bus segment length is
4,000 ft. (1,219 m) using recommended wire. Repeaters
must be used when making runs longer than 4,000 ft.
(1,219 m). A maximum of three repeaters can be used
between any two devices.
MS/TP MAC Address
The MS/TP MAC address for each device must be set to a
unique value in the range of 0-127 on an MS/TP network
segment. The MAC address is set using the installer setup
menu through the device’s display. The factory default
MAC address is 0.
Device Instance Number
The Device Instance Number must be unique across the
entire BACnet system network because it is used to
uniquely identify the BACnet devices. It may be used to
conveniently identify the BACnet device from other devices
during installation. The Device Instance Number is set
using the installer setup menu through the device’s display
or over the BACnet network. The Device Instance Number
can be changed by the user, which may be necessary when
integrating with a third party or when attempting to replace
an existing device and it is desired to maintain the existing
Device Instance Number. The factory default Device
Instance Number is 0009999 and can range from
0-4194302.
NOTE: For complete instructions on how to set the
MS/TP MAC address or set the Device Instance
Number refer to the Installation Instructions, form
31-00093.
Termination Resistors
Matched terminating resistors wired across MS/TP+ and
MS/TP– are required at the last device on each end of the
MS/TP segment for signal integrity.
Optimum segment performance typically requires “tuning,”
a process by which the value of the terminating resistors is
selected based on the wave form of signals on the
segment. View wave forms using an industrial scope meter.
The goal is to have as square a wave form as possible with
an amplitude greater than 200 mV. Resistors affect the
wave form as follows:
• When the resistance value decreases, the amplitude of
the wave form decreases and becomes more square.
• When the resistance value increases, the amplitude of
the wave form increases and becomes less square.
Typically, precision resistors in the range 80-130 Ohms
(+1%) yield acceptable results. Ideally, the value of the
terminating resistors should match the rated characteristic
impedance of the installed cable. For example, if the
installed
MS/TP cable has a listed characteristic impedance of 100
Ohm, install 100 Ohm matched precision resistors.
Grounding MS/TP LAN Shield
Proper shield grounding of the MS/TP cabling can help
minimize the risk of communications problems and
damage to equipment because of transient voltage spikes
(for example, lightning strikes).
Follow these guidelines for grounding MS/TP cable
shields:
• Each MS/TP segment should have a single point of
shield ground, preferably as close to the middle of the
cabling run as possible.
• Do not ground the MS/TP shield using a BACnet FF
terminal.
• Never ground both ends of a shield; differences in
potential between the grounds may induce current on
the shield, causing interference.
• At termination connecting points, tie the shield through
with a wire nut.
• At ungrounded, exposed shield points (the end of a
segment), tape back the shield to the wire jacket or, for
optimum transient shunting, use 100 V gas discharge
tubes or 120 V MOVs between shield and ground.
* Refer to the PICS (Protocol Implementation Conformance
Statement) for complete details, 31-00102.
Accessories
— 50037735-001 Wireless door/window sensor
— 50037736-001 Wireless passive infrared (PIR)
motion sensor
Table 2. BACnet Interoperability Building Blocks (BIBBs)
Supported.*
DS-RP-A,B DM-DOB-B
DS-RPM-B DM-DCC-B
DS-WP-A,B DM-PT-A,B
DS-WPM-B DM-TS-B
SCHED-I-B DM-UTC-B
DM-DDB-A,B DM-RD-B