Sequence of Operation
RTU Open v3 Carrier Proprietary and Confidential CARRIER CORPORATION ©2016
Integration Guide All rights reserved
27
status may be configured on any unused binary input channel. A typical application is a differential pressure
switch that senses the pressure drop across a filter bank.
When the pressure across the filter bank exceeds the setpoint of the differential pressure switch, the
status
is displayed as
on the controller graphic. An alarm indicates a dirty filter.
Some of the
functions described in this section will only be visible on the
page >
tab >
when the appropriate inputs are configured. Alarms are not initiated when the input is
not configured.
- You may use the RTU Open's safety chain circuit to shut down the unit for a safety condition.
Examples: Low or High Temperature Cutouts (Freezestat / Firestat). This alarm indicates the safety chain circuit
(Input 4) is open. Cooling, heating, and supply fan operation stop after appropriate time guards. Normal operation
resumes when the safety chain circuit is complete.
- You may configure the RTU Open to accept a
contact on Input 5.
Examples: Smoke detectors or fire shutdown relays. This alarm indicates this device (Input 5) has tripped. Cooling,
heating, and supply fan operation immediately stop. Reset fire shutdown contact to resume normal operation.
– If configured for the IGC input function, the RTU Open will compare the state of this input with the
requirement for heat (W1 or W2). If the IGC input, which detects an active flame in the gas heat section, is present
1 minute after any call for heating has ended, a gas valve failure alarm will occur, indicating a stuck gas valve.
– You may configure the RTU Open to monitor the base unit’s compressor safety circuit. This
alarm indicates the base unit's compressor safety circuit is energized. Cooling, heating, and supply fan outputs are
not interrupted except when the RTU Open is configured for Heat Pump. Normal operation resumes when the
compressor safety circuit is de-energized.
If the Heat Pump is a HP O/B Ctrl type and is in the heating mode, it will automatically replace the compressor
stage(s) with the equivalent number of auxiliary heat stages, as available.
• If it's a Carrier Heat Pump HP Y1/W1 Ctrl, there is only 1 auxiliary heat stage output and the staging is done
by the machine itself. The RTU Open control does not take any action.
• For a non-Carrier Heat Pump, when configured for 2 stages of aux heat and two compressors, Compressor 1
is replaced by Aux Heat Stage 1 and Compressor 2 is replaced by Aux Heat Stage 2.
The compressor output stays on when the safety alarm is present. For cooling, the alarm indicates the
compressors are not operating. See Heat Pump operation (page 24) for further information.
– This alarm indicates if the space temperature is outside the configured alarm limits. If
active (Alarm), displays additional values for the space temperature when the alarm condition occurred and the
alarm limit exceeded.
The following values are related to the
alarm:
•
– Displays the value of the space temperature that caused the alarm condition to
occur and is only visible when the
is in an alarm state.
•
– Displays the value of the alarm setpoint that was exceeded by the alarming
temperature and is only visible when the
is in an alarm state.
– This alarm indicates a communication failure of a connected SPT sensor that previously had been
actively communicating. The alarm is reset when normal SPT sensor communications resume, if power is cycled to
the controller, or if the
point is set to
.
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