Communications wiring
Unit Ventilator
CARRIER CORPORATION ©2019
Integration Guide
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12
4
Set DIP switches
1
and
2
for the appropriate communications speed. See table below.
NOTE
Use the same baud rate for all devices on the network segment.
Baud Rate
1
2
9,600
bps
Off
Off
19.2
kbps
Off
On
38.4
kbps
On
Off
76.8
kbps
On
On
5
Set DIP switch
3
OFF and
4
ON for Modbus.
The following example is set for 38.4 kbps and Modbus.
6
Connect the communications wiring to the
Comm
port in the screw terminals labeled
Net +
,
Net -
, and
Shield
.
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.
7
Turn on the power for the Unit Vent by connecting power terminals.
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 Modbus (8 Data bits, No Parity, and 1 Stop bit):
Baud rate DIP switches 1 and 2
Protocol DIP switches 3 and 4
