Wiring Guidelines - Honeywell TB7600 Integration Manual

WIRING GUIDELINES

Overview
Honeywell uses EIA-485 as the physical layer between their devices and supervisory controllers
For clarity we will use the term "Device" to represent any product with an active EIA-485 network connection, including Honeywell
and non-Honeywell thermostats.
Parameter
Media
Characteristic Impedance
Distributed capacitance
Maximum length per segment
Polarity
Multi-drop
Terminations
Maximum number of nodes per segment
Maximum number of nodes per network
Baud rate
Cable Type
Honeywell recommends the use of balanced 22-24 AWG twisted pair with a characteristic impedance of 100-130 ohms,
capacitance of 30 pF/ft or lower. A braided shield is also recommended.
Impedance
A value based on the inherent conductance, resistance, capacitance and inductance that represent the impedance of an infinitely
long cable. The nominal impedance of the cable should be between 100Ωand 120Ω. However using120Ω will result in a lighter
load on the network.
Capacitance (pF/ft)
The amount of equivalent capacitive load of the cable, typically listed in a per foot basis. One of the factors limiting total cable
length is the capacitive load. Systems with long lengths benefit from using low capacitance cable (i.e. 17pF/ft or lower).
BACNET INTEGRATION MANUAL FOR TB7600 SERIES THERMOSTATS
Table 2. Summary of Specifications for a Honeywell EIA-485 Network
Twisted pair 22AWG-24 AWG, shielded recommended
100-130 ohms
Less than 100 pF per meter (30 pF per foot)
1200 meters (4000 feet)
Polarity sensitive
Daisy-chain (no T connections)
1. A TB7600, TB7300, or TB7200 device is installed at one end of
2. Other devices are installed at both ends of the MS/TP net-
64 (Honeywell devices only)
128
9600, 19200, 38400, 76800 (Auto detect)
TB7600, TB7300, and/or TB7200 Series thermostats are
installed at both ends of the MS/TP network: 120 Ohms resistor
should be installed at each end. To reduce issues with other
BACnet devices we recommended keeping like devices on the
same bus. TB7600, TB7300 and TB7200 Series thermostats can
be installed on the same bus.
the MS/TP network and another device is installed at the other
end:
Install an End-Of-Line resistor value that matches the other
device's instructions regarding the End-Of-Line resistors
work:
Follow the other device's instructions regarding the End-Of-Line
resistors.
3
Details
63-4523—02