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RTU Open 51
• For a non-Carrier Heat Pump, when configured for two 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 down. See Heat Pump operation (page 48) for further information.
Space Temp Sensor – This alarm indicates an invalid sensor condition in a physically connected space
temperature sensor (SPT Sensor/T5*). Cooling, heating, and supply fan operation stop after the appropriate
time guards. Normal operation resumes when the controller detects a valid sensor.
Supply Air Temp Sensor – This alarm indicates a shorted or open circuit in the SAT input. Cooling, heating,
and supply fan operation stops after the appropriate time guards. Normal operation resumes when the
controller detects a valid sensor.
Outdoor Air Temp Sensor Alarm - This alarm indicates a shorted or open circuit in the OAT input. Cooling,
heating, and supply fan operation continues. OAT lockouts will not operate while the sensor is in alarm.
Normal operation resumes when the controller detects a valid sensor.
Space Relative Humidity Sensor - This alarm indicates if the mA input at the associated channel falls below
3.5 mA or rises above 21 mA. Cooling, heating, and supply fan operation continues, however, the controller’s
Humidi-MiZer™ binary output is disabled until the fault condition is corrected.
IAQ Sensor - The RTU Open generates an IAQ Sensor alarm if the mA input at the associated channel falls
below 3.5 mA or rises above 21 mA. Cooling, heating, and supply fan operation continues. However, the
controller’s IAQ control function is disabled until the fault condition is corrected.
OAQ Sensor - The RTU Open generates an OAQ Sensor alarm if the mA input at the associated channel falls
below 3.5 mA or rises above 21 mA. Cooling, heating, and supply fan operation continues. However, the
controller’s IAQ control function uses 400ppm as the fixed outdoor air CO2 level until the fault condition is
corrected.
Space Temperature –
• Occupied - The RTU Open generates a Low Space Temperature alarm if the space temperature falls
below the lower limit of the blue color bar. A
High Space Temperature alarm is generated if the space
temperature rises above the upper limit of the orange color bar.
• Unoccupied An unoccupied low space temperature alarm is generated when the space temperature falls
below the
Alarm Configuration > Unoccupied Low SPT Alarm Limit. An unoccupied high space
temperature alarm is generated when the space temperature rises above the
Alarm Configuration >
Unoccupied High SPT Alarm Limit.
The following values are related to the Space Temperature alarm:
• Alarming Temperature – This variable displays the value of the space temperature that is in alarm and is
only visible when the space temperature is in an alarm state.
• Alarm Limit Exceeded – This variable displays the value of the alarm setpoint that is exceeded by the
alarming space temperature and is only visible when the space temperature is in an alarm state.
High Supply Air Temperature – The RTU Open generates this alarm when the supply air temperature exceeds
the
Alarm Configuration > High SAT Alarm Limit setpoint for 5 minutes. This alarm is inhibited until the RTU
has been running for 30 minutes to allow for system stabilization after startup.
Low Supply Air Temperature - The RTU Open generates this alarm when the supply air temperature falls
below the
Alarm Configuration > Low SAT Alarm Limit setpoint for 5 minutes. This alarm is inhibited until the
RTU has been running for 30 minutes to allow for system stabilization after startup.
Setpoint Slider – The RTU Open generates this alarm when an open circuit is detected at Input 11 and the
RTU Open
Configuration > Unit Configuration > Input Configuration > Space sensor type is set to T56. Note
that only an open circuit results in an alarm. A short across this input offsets the setpoints negatively by the
amount configured in the
Unit Configuration > Setpoint Adjustment Range.
Switch Configuration - The RTU Open generates this alarm when any two of the Unit Configuration > Input
Functions 3, 5, 8, or 9 are configured identically. Neither input may work reliably and downstream control may
be affected, depending on the function duplicated. The alarm clears and normal control is restored when the
input function duplication is corrected.
Analog Input Configuration - The RTU Open generates this alarm when the Unit Configuration > Input