McQuay MicroTech III RAH User Manual

60 McQuay OM 920-1
Alarms
Faults
Airflow Fault
If differential pressure switch PC7 fails to detect airflow for longer than the airflow timer
(default = 120 seconds) 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 problem described above has first occurred twice within the
previous twenty-four hour period. The conditions that cause the Fan Retry problem and the
action taken are the same as for the Fan Fail fault with the difference being that the Fan Retry
alarm is an automatically clearing alarm 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.
Low Discharge Air Temperature
If the unit is not in the Mechanical Cooling 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 Temp
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.
High Return Air Temp
If the Return Air Temperature is greater than the Return Air Temperature Limit (Default =
120°F) and the supply fan has been on for longer than the temperature alarm delay (Default =
30 seconds), the High Return Air Temperature fault occurs. When the High Return Air
Temperature fault occurs, the unit is shut down. It remains shut down until the High Return
Air Temperature fault is manually cleared through the unit keypad or via a network signal.
Duct High Limit Fault
If the unit is Variable Air Volume, the contacts of the duct high pressure limit control (DHL)
open, and the Unit State is not Off or Startup, the Duct High Limit fault occurs. When the Duct
High Limit fault occurs, the unit is shut down. The unit remains shut down until the Duct High
Limit fault is manually cleared through the unit keypad or via a network signal.
Discharge Air Sensor Fault
If the discharge air temperature sensor (DAT) is open or short circuited for longer than the
Sensor Alarm Delay (Default= 30 seconds), the Discharge Air Sensor fault occurs. When the
Discharge Air Sensor fault occurs, the unit is shut down. It remains shut down until the
Discharge Air Sensor fault is manually cleared through the unit keypad or via a network
signal.

McQuay MicroTech III RAH Specifications

General

Brand	McQuay
Model	MicroTech III RAH
Category	Controller
Language	English