Ms/Tp Lan Wiring - Honeywell TB3026B Installation Instructions Manual

Fig. 4. Fixed Function Thermostat terminal assignments
WARNING
Do not apply line voltage to source pins.
A jumper is pre-installed between pins 1 and 2. The
jumper supplies 24 VAC to BO-1, BO-3, and BO-4. It can
be removed if those BOs are powered from an external
source. (Note: BO-0, BO-2, and BO-5 are powered from the
board.)
Refer to BACnet Fixed Function Thermostat System
Engineering Guide (31-00098) for complete application
wiring examples.
Table 1. Terminal Identification.
Terminal Label
1 24VAC
2 RELAY 24VAC
3 BO0
4 BO1
5 GND
6 AI0
7 COM
8 AI1
9 COM
10 AI2
11 MS/TP -
12 MS/TP +
13 AO1
14 COM
15 AO0
16 GND
17 BO2
18 BO3
19 BO4
20 BO5
Connection
24 VAC Power
24 VAC Power
Relay Output
Relay Output
Ground
Universal Input
Common
Universal Input
Common
Universal Input
BACnet ® Communications
BACnet ® Communications
Analog Output
Common
Analog Output
Ground
Relay Output
Relay Output
Relay Output
Relay Output
BACNET® FIXED FUNCTION THERMOSTAT

MS/TP LAN Wiring

The BACnet FF communicates on the site-wide BACnet
system over a twisted-pair MS/TP LAN, which uses the
EIA–485 signaling standard. The BACnet FFs are master
devices on the MS/TP LAN.
Each BACnet FF employs a high-quality EIA–485
transceiver and exerts 1/4 unit load on the MS/TP LAN.
Table 2. MS/TP LAN facts.
Transmission 9.6, 19.2, 38.4, 76.8Kbps (configured at
speed global controller).
Layout Bus.
Cabling BACnet specifies the following. Shielded,
twisted-pair cabling with characteristic
impedance between 100 and 130W.
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 4000 ft. (1071 m.) per segment using
length recommended wire.
Maximum Depends on classification of devices as
devices master or slave. Maximum number of
overall master devices is 128. Maximum number
of slave devices or devices overall (mixed
master and slave) is 255. This includes
BACnet FFs, BACnet global controllers (all
are considered masters) and any other
devices, regardless of their relative unit
loads.
Maximum Depends on relative unit load of devices
devices per (see "Terminating MS/TP LAN Cabling" on
segment page 3).
Repeaters Required when making runs longer than
4000 ft. Three repeaters maximum
between any two devices.
Terminating Matched resistors required at each end of
resistors segment bus wired across (+) and (–). Use
matched precision resistors rated |
1/4 W ±1% / 80 - 130 Ohms.
Shield Ground shield drain wire at single point
grounding earth (panel) ground, not BACnet FF
ground. Tape off shield drain wire at other
end. Tie shield drain wire through at each
BACnet FF.
Terminating MS/TP LAN Cabling
MS/TP terminations are located on the lower left of the
BACnet FF wallplate.
Maintain polarity of the MS/TP wire run throughout the
MS/TP LAN.
3 31-00093—01