Sensor Faults And Failures; Fault Sequences - Daikin MicroTech Operation And Maintenance

Sensor Faults and Failures

Fault Sequences

Emergency Stop/Shutdown Discrete Input
Name: ShutdownDIAlarm
Description: A configured binary input is telling the unit to stop/
shutdown.
Type: Fault
Activate: Unit is configured to have a shutdown input installed
and the associated binary input is closed.
Upon active:
• Alarm type is Fault which causes unit shutdown
• State: Off Alarm
• Alarm is indicated on the LUI
• Fault relay is NOT energized
• LED output alarm indication is activated
• Space fan is immediately de-energized
• Compressor is immediately de-energized
• Outdoor fan is immediately de-energized
• Outside air damper is forced closed
• All electric heat stages are de-energized
• Face and bypass damper is positioned to bypass
• Heat/cool valves are fully closed to the coil
Deactivate: Shutdown binary input is opened.
Reset: Auto
Note: This does not power the unit off, but does halt operation.
Space Temp Sensor Failure
Name: SpaceTempSensorAlarm
Description: Space Temp Sensor Failure (short or open
detected)
Type: Problem
Activate: Appropriate input is configured for a space
temperature sensor and the sensor reading is out of range for
30 seconds.
Upon active:
• Control temp will be based on return temp if available.
If return temp is not available then ControlTempAlarm
becomes active
• Fault relay is energized if alarm output configuration is
FAULTPROB
• LED output alarm indication is activated
Deactivate: Sensor reading goes back in range
Reset: Auto
OM 1280-2 • MICROTECH UNIT CONTROLLER
High DX Pressure Fault
Name: HighDxPressureAlarm
Description: High refrigerant pressure fault.
Type: Problem
Activate: Unit is configured to have a high pressure switch
installed and the associated binary input is open.
Upon active:
• State:
— If in cooling state then transition to a non-DX cooling
state, if available, otherwise transition to Prepare to
Cool
— If in heating then transition to a non-DX heating state,
if available, otherwise transition to Prepare to Heat
• Alarm is indicated on the LUI
• Fault relay is energized if alarm output configuration is
FAULTPROB
• LED output alarm indication is activated
• Compressor is immediately de-energized
• Outdoor fan is de-energized
• Use Electric heat if possible
Deactivate: High pressure binary input closes
Reset: 2-Auto in 7-days then niResetAlarm or LuiResetAlarm
must become CLEAR_ALARM
Discharge Air Temperature Low Limit DX
Name: DATLLDxAlarm
Description: Discharge air temperature has gone lower than
the discharge air Mechanical Cooling Low Limit setpoint during
compressorized cooling.
Type: Problem
Activate: Discharge Air Temperature <= Mechanical Cooling
Low Limit and the unit is in compressor cooling.
Upon active: (describes what happens in other modules)
• State: Prepare to Cool
• Alarm is indicated on the LUI
• Fault relay is energized if cpAlarmBOut is FAULTPROB
• LED output fault indication is activated
Deactivate: Discharge Air Temperature > Mechanical Cooling
Low Limit + 1.8F
Reset: Auto reset
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