Carrier RTU OPEN 11-808-427-01 - Manual (Page 17)

RTU Open 11
Wiring the RTU Open to the MS/TP network
The RTU Open communicates using BACnet on an MS/TP network segment communications at 9600 bps,
19.2 kbps, 38.4 kbps, or 76.8 kbps.
Wire the controllers on an MS/TP network segment in a daisy-chain configuration.
Install a BT485 on the first and last controller on a network segment to add bias and prevent signal
distortions due to echoing.
See the MS/TP Networking and Wiring Installation Guide for more details.
Wiring specifications
Cable: 22 AWG or 24 AWG, low-capacitance, twisted, stranded, shielded copper wire
Maximum length: 2000 feet (610 meters)
To wire the controller to the network
1 Pull the screw terminal connector from the controller's power terminals labeled Gnd and 24 Vac or Hot.
2
Check the communications wiring for shorts and grounds.
3 Connect the communications wiring to the BACnet port’s screw terminals labeled Net +, Net -, and
Shield .
NOTE Use the same polarity throughout the network segment.
4 Verify that the MSTP jumper is set to MSTP.
5 Set DIP switches 1 and 2 to the appropriate baud rate. See the MSTP baud diagram on the RTU Open.
The default baud rate is 76.8 kbps.
NOTE
Use the same baud rate for all controllers on the network segment.