Emerson Liebert Challenger With Liebert iCOM Control 3000/ITR - Manual (Page 35)

Operation
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Pump Down—Air Cooled with Condenser Only Units
The Pump Down operation is performed to protect the compressor oil from being diluted with liquid
refrigerant, which helps ensure that the compressor is properly lubricated for the next startup. The
Pump Down operation operates in the following manner:
Pump down is always performed loaded (for digital scroll: control solenoid valve disabled).
Digital Scroll Only: When pump down has finished successfully, pump down will be continued for
another half-second with the control solenoid valve energized.
High Pressure Alarm
When the compressor is initially activated, the system will be monitored for a high pressure situation.
When a high pressure situation is detected during the first 10 minutes of operation, the unit will
attempt to correct the problem several times without notification. This alarm will automatically reset
when the pressure drops to an acceptable operating range. If the unit is unsuccessful in correcting the
problem, an alarm will occur and the affected compressor will be locked Off. If high head pressure
alarm trips three times in a rolling 12 hour period, the affected compressor will be locked Off.
Once the compressor is locked Off, it will not come back On until main power is reset, or until the
HP Alarm Counters (Service Menu, Diagnostics) are reset to 0.
Digital Scroll High Temperature
A protective maximum operating compressor temperature limit is imposed on units with digital scroll
compressor(s) with thermistor. Once the digital scroll temperature reaches the maximum tempera-
ture threshold, the compressor will be locked out for at least 30 minutes and an alarm will be annun-
ciated. If after 30 minutes the temperature has cooled to a safe operating temperature, the
compressor will resume operation.
The HT 1 Alarm Counter (Service Menu, Diagnostics) records the number of high-temperature
alarms. Once these counters reach five occurrences in a rolling four-hour period, the compressor will
be locked out. The alarm can be reset once the temperature returns to a safe level by:
1. Setting the counter back to 0 from the display and pressing the alarm reset button.
2. Shutting Off power to the control board by turning the cooling unit's main power disconnect
switch Off and On.
5.1.3 Compressor Timing
To help maximize the life of your compressor(s), there is a start-to-next start delay for each single
compressor.
A Minimum On time and a Minimum Off time may be selected in the Advanced menu (minimum
three minutes for single phase compressors). Consult the factory on how to modify the Minimum On
and Off time settings.
NOTE
Pump down activation is determined by the type of unit; these units do not have a pump-down
function: Glycol, GLYCOOL and remote condensing units.
NOTE
If the unit is equipped with manual reset high head pressure switches, or if the auto reset high
head pressure switches don’t reset, the compressor will not be turned back On, but there will be
a 30-second delay from when the high head pressure situation occurs and when the alarm is
annunciated.