Faults - Daikin MicroTech III Operation Manuals

Freeze Problem - (Freeze: Problem)
When a unit is equipped with a waterside economizer, chilled
water, hot water, or steam coil, the Freeze problem occurs
when the optional freezestat contacts open as a result of
detecting an abnormally low water or steam coil temperature
while the fans are off .
When the Freeze problem occurs, the controller opens the
waterside economizer valve, chilled water and heating valves,
and sets a 10-minute timer . If the unit is equipped with a
waterside economizer, the pump output is also turned on .
When the 10-minute timer expires, the controller checks the
freezestat input again . If the freezestat contacts are closed
the pump output is de-energized and the valves close . If the
freezestat contacts are still open the pump output remains
energized, the valves remain open, and the 10-minute timer
resets . This continues while the unit remains off . Whenever
the freezestat closes the Freeze problem automatically clears .
This feature protects the coil(s) and allows the system to start
normally when an occupied command is received .
Heat Fail Problem - (Heat Fail: Problem)
If an RPS unit is equipped with a Daikin gas furnace and
the burner flame safeguard (FSG) control enters the "safety
lockout" state after a call for heat, a digital input is provided to
EXP B-X4 on the controller . When this digital input is present
the Heat Fail problem occurs . When the Heat Fail problem
occurs, the unit continues to operate with the heating system
disabled by the FSG. Heating remains disabled until the flame
safeguard control is manually reset . The heat fail problem
clears automatically when the FSG control is reset .
OM 920-6 • MICROTECH UNIT CONTROLLER

Faults

Airflow Fault - (Airflow: Fault)
If differential pressure switch PC7 fails to detect airflow for
longer than the airflow timer (default = 120 seconds) and on
VAV units the current duct static pressure indication is less than
half the static pressure setpoint after the unit leaves the Startup
operating state or any time afterward, while the unit is running,
the Fan Fail fault occurs . When the Fan Fail fault occurs, the
unit is shut down . It remains shut down until the Fan Fail fault
is manually cleared through the unit keypad or via a network
signal . On units equipped with a discharge fan VFD, the Fan
Fail fault only occurs if the Fan Retry condition described
above has first occurred twice within the previous twenty-four
hour period . The conditions that cause the Fan Retry and the
action taken are the same as for the Fan Fail fault with the
difference being that the Fan Retry is automatically reset once
the unit is shut off . This allows the unit to attempt to restart up
to three times within a twenty-four hour period .
NOTE: There is no Fan Retry function or three retry function
when a unit has a CAV supply fan .
If Modbus communication is lost between the MCB
and the supply fan VFD the duct static pressure is not
considered in the Fan Fail logic .
Low Discharge Air Temperature - (Lo Disch Temp:
Fault)
If the unit is not in the operating state and the discharge air
temperature is less than the Low Discharge Temperature Limit
(Default = 40°F) for longer than 30 seconds and the supply
fan has been on for longer than the LowDAT temperature
alarm delay (Default = 6 minutes), the Low Discharge Air
Temperature fault occurs . When the Low Discharge Air
Temperature fault occurs, the unit is shut down . It remains shut
down until the Low Discharge Air Temperature fault is manually
cleared through the unit keypad or via a network signal .
High Discharge Air Temperature - (Hi Disch Temp:
Fault)
If the discharge air temperature is greater than the High
Discharge Temperature Limit (Default = 170°F) and the supply
fan has been on for longer than the Temperature Alarm Delay
(Default = 30 seconds), the High Discharge Air Temperature
fault occurs . When the High Discharge Air Temperature fault
occurs, the unit is shut down . It remains shut down until the
High Discharge Air Temperature fault is manually cleared
through the unit keypad or via a network signal .
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