Carrier PrimeLINE 69NT40-561-200, Operation And Service Manual

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4–29 T-362
• During QUEST pulldown, supply air temperature is lowered somewhat relative to the nominal setpoint.
Evaporator fans are forced to operate at high speed.
Steady-state QUEST mode control maintains the same lowered supply air temperature that was used during
QUEST pulldown. The compressor cycles on and off according to return air high and low limits. Depending on the
fan mode of operation selected, the evaporator fans may be programmed to run at low speed some or all of the
time according to the control logic.
4.4 Controller Alarms
Alarm display is an independent controller software function. If an operating parameter is outside of expected
range or a component does not return the correct signals back to the controller, an alarm is generated. A listing of
alarms is described in
Table 4–5
.
The alarm philosophy balances the protection of the refrigeration unit and that of the refrigerated cargo. The action
taken when an error is detected always considers the survival of the cargo. Rechecks are made to confirm that an
error actually exists.
Some alarms requiring compressor shutdown have time delays before and after to try to keep the compressor on
line. An example is alarm code “LO,” (low main voltage), when a voltage drop of over 25% occurs, an indication is
given on the display, but the unit will continue to run.
When an Alarm Occurs:
• The red alarm light will illuminate for alarm code numbers 15, 17, 20, 21, 22, 23, 24, 25, 26, and 27.
• If a detectable problem exists, its alarm code will be alternately displayed with the setpoint on the left display.
• The user should scroll through the alarm list to determine what alarms exist or have existed. Alarms must be
diagnosed and corrected before the Alarm List can be cleared.
To Display Alarm Codes:
1. While in the Default Display mode, press the ALARM LIST key. This accesses the Alarm List Display mode,
which displays any alarms archived in the alarm queue.
2. The alarm queue stores up to 16 alarms in the sequence in which they occurred. The user may scroll
through the list by pressing an Arrow key.
3. The left display will show “AL##,” where ## is the alarm number sequentially in the queue.
4. The right display will show the actual alarm code. “AA##” will display for an active alarm, where “##” is the
alarm code. Or “IA##” will display for an inactive alarm. See Table 4–5 for alarm listing.
5. “END” is displayed to indicate the end of the alarm list if any alarms are active.
6. “CLEAr” is displayed if all alarms are inactive. The alarm queue may then be cleared by pressing ENTER.
The alarm list will clear and “-----” will be displayed.
NOTICE
AL26 is active when none of the sensors are responding. Check the connector at the back of the
controller, if it is loose or unplugged, reconnect it, then run a pre-trip test (P5) to clear AL26.