Communications wiring
RTU Open v3
Carrier Proprietary and Confidential
CARRIER CORPORATION ©2016
Integration Guide
All rights reserved
6
Protocol overview
Protocols are the communication languages spoken by the control devices. The main purpose of a protocol is to
communicate information in the most efficient method possible. Different protocols exist to provide specific
information for different applications.
In the BAS application, many different protocols are used, depending on manufacturer. Different protocols do not
change the function of the controller, but they typically require the owner to change systems or components in
order to change from one protocol to another. The RTU Open is an effective solution to minimize the amount of
controllers that you may need to change in order to communicate with different types of protocols.
You can set the controller to communicate 1 of 4 different protocols:
•
BACnet MS/TP
(page 7)
•
Modbus
(page 9)
•
N2
(page 12)
•
LonWorks
(page 14)
The default setting is BACnet MS/TP. Switch 3 (
SW3
) on the board sets protocol and baud rate. Switches
MSB
(
SW1
) and
LSB
(
SW2
) set the board’s network address. See table below for specific switch settings. The third
party connects to the controller through port
J19
for BACnet MS/TP, Modbus, and N2, and through
J15
for the
LonWorks Option Card.
NOTES
•
Changing protocol requires no programming or point assignment by the installer or operator.
•
Power must be cycled after changing the
MSB
(
SW1
) -
LSB
(
SW2
) settings or connecting the LonWorks Option
Card to
J15
.
SW3 Switch Settings Table
Protocol Selection
Baud Rate
Protocol
DS8
DS7
DS6
DS5
DS4
DS3
DS2
DS1
BACnet MS/TP
(Default)
Master Unused Off
Off
Off
On
Off
Select Baud Select Baud
Modbus
Slave
Unused Off
Off
On
On
Off
Select Baud Select Baud
N2
Slave
Unused Off
Off
Off
On
On
Off
Off
Lonworks
Unused On
On
Off
On
Off
Off
On
Baud Selection Table
Baud Rate
SW3/DS2
SW3/DS1
9,600
Off
Off
19,200
On
Off
38,400
Off
On
76,800
(Default)
On
On
Communications wiring