Communications wiring
RTU Open v5
CARRIER CORPORATION ©2019
Integration Guide
All rights reserved
12
4
Set the remaining DIP switches as follows:
Modbus DIP switch settings
8
7
6
5
4
3
Off
Off
Off
On
On
Off
The following example shows the DIP switches set for 9600 baud and Modbus.
5
Connect the Modbus EIA-485 network to the RTU Open's
J19
Network Comm
port. Connect to
Net+
,
Net-
,
and
SHLD
.
Wire specifications
○
A dedicated 22 AWG shielded twisted pair wire (EIA 485)
○
Maximum wire length 2000 feet (610 meters) or 32 nodes
○
Devices should be daisy-chained and not star-wired
○
Attach the drain/shield wire to both ends of the network segment and through every controller
NOTE
Use the same polarity throughout the network segment.
6
Turn
on
the RTU Open's power.
Troubleshooting Modbus communication
The most common communication problems result from not properly following the configuration steps outlined
above in this manual. Review all of the steps and use the following list to check your settings.
Verify accuracy of the following:
Hardware settings
for speaking Modbus (8 Data bits, No Parity, and 1 Stop bit):
Baud rate DIP switches DS2 and DS1
Protocol DIP switches DS3 - DS6
