Distech Controls RT Series User Manual

11
BACnet Wiring Guide
Overview
Distech Controls 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 Distech Controls and non-Distech Controls controllers.
Summary Specifications:
Parameter
Details
Media
Twisted pair 22AWG-24 AWG, shielded recommended
Characteristic Impedance
100-130 ohms
Distributed capacitance
Less than 100 pF per meter (30 pF per foot)
Maximum length per segment
1200 meters (4000 feet) Note: AWG 18 cable
Polarity
Polarity sensitive
Multi-drop
Daisy-chain (no T connections)
Terminations
1. Distech Controls’ thermostats are installed at both
ends of the MSTP network:
120 Ohms resistor should be installed at each end.
2. A Distech Controls thermostat is installed at one end of
the MSTP network and a 3
rd
party device is installed at
the other end:
Install an End-Of-Line resistor value that matches the 3 rd
party device instruction regarding the End-Of-Line resistors
3. 3
rd
party devices are installed at both ends of the MSTP
network:
Follow the 3
rd
party device instructions regarding the End-
Of-Line resistors.
Network Bias Resistors
510 ohms per wire (max. of two sets per segment)
Maximum number of nodes per
segment
64 (Distech Controls devices only)
Maximum number of nodes per
network
128
Baud rate
9600, 19200, 38400, 76800 (Auto detect)
Table 1: Summary of Specifications for a Distech Controls’ EIA-485 Network

Distech Controls RT Series Specifications

General

Brand	Distech Controls
Model	RT Series
Category	Thermostat
Language	English