Troubleshooting
RTU Open v5
CARRIER CORPORATION ©2019
Integration Guide
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38
The RTU Open controller acts as an intelligent embedded thermostat to the rooftop unit, but can be monitored and
controlled from a third party network. For this reason, there are 3 distinct components for troubleshooting.
The three parts to the system are:
The mechanical systems of the rooftop unit
The RTU Open controller
The third party network connected
Determining which component needs troubleshooting is the first step.
The RTU Open controller can be used to troubleshoot itself with service test, communicating LED’s, and built-in
alarms, which are discussed in the unit Controls and Troubleshooting instructions. Disconnecting the RTU Open
from the unit control inputs can be valuable in determining whether the problem is related to the unit/equipment,
the controller/equipment, or the controller/network. Generally, this should be the first step in troubleshooting
operational problems. When disconnected from the unit control inputs, simple 24V signals can be used to activate
the units G, Y1, Y2, W1, W2, etc. and verify proper unit operation. If the problem occurs without the RTU Open
connected, then the operator should begin troubleshooting the unit/equipment rather than the RTU Open or
network.
Third party network may also help in troubleshooting the controller and rooftop unit. Third party network
troubleshooting may also be required.
LED's
The LED’s indicate if the controller is speaking to the other devices on the network. The LED’s should reflect
communication traffic based on the baud rate set. The higher the baud rate, the more solid the LED’s will appear.
The LED's on the RTU Open show the status of certain functions.
If this LED is on...
Status is...
Power
The RTU Open has power.
Rx
The RTU Open is receiving data from the network segment
Tx
The RTU Open is transmitting data over the network segment
BO#
The binary output is active
NOTE
If Tx is not lit, the MS/TP token is not being passed between controllers.
The
Run
and
Error
LED's indicate controller and network status.
If Run LED shows...
And Error LED shows...
Status is..
2 flashes per second
Off
Normal
2 flashes per second
2 flashes,
alternating with
Run
LED
Five minute auto-restart delay after
system error
2 flashes per second
3 flashes, then off
Controller has just been formatted
2 flashes per second
On
Two or more devices on this network
have the same network address
Troubleshooting
