Emerson Liebert iCOM Training And Service Manual page 44

iCOM
Control Training and Service Manual
DigiScroll compressors
Note: On units with Digital Scroll Compressors the unloader is energized 0.1
second before the compressor contactor is energized.
Let the compressor run @ 50% capacity for the LPDT value. For the last 30
seconds of the LPDT value, run compressor at 100%. If at the end of the LPDT
time the switch is closed the flow moves to "Loss of Charge Protection" (Phase 3),
and Phase 1 is finished. The "flow" is now in Phase 3, Loss of charge
protection. The "flow" checks about having the digital input continuously OK for 5
seconds. If so, continue operation.
Low Pressure Phase Conditions
Failure in Phase 1
If Phase 1 is elapsed, the "flow" moves to Phase 4, with a maximum waiting time
of 5 minutes, where it is looking for a single reading to be OK. If OK, then "flow"
moves to "Loss of charge protection".
NOTE: The compressor is OFF, no Pump down, LLSV is OPEN.
Failure in Phase 4
If pressure is not reached in Phase 4, the "flow" moves to phase 5: Sound an
alarm (Code 1), stop the compressors, leave the LLSV open, no pump down; and
waits a single reading to be above threshold 1 to move to Phase 3, "Loss of
charge protection". This waiting phase will last forever or as long as there is a call
for cooling. The compressor may operate during the alarm is active, once the
pressure conditions allow for it (see above).
Phase 3
After Phase 1, once the pressure input is NOK, the "flow" moves to Phase 8: Waits
5 minutes to reach one single OK reading. If OK continue operation, if NOK then
move to Phase 9 and sound an alarm (Code 3), stop the compressors, leave LLSV
open, no pump down; and continue to wait a single OK to start normal compressor
operation. This waiting phase will last forever or as long as there is a call for
cooling. The compressor may operate during the alarm is active, once the
pressure conditions allow for it (see above).
Pump Down
If the pump down parameter is enabled, anytime a compressor is turned OFF and
the low-pressure switch is closed (pressure OK), the compressor will be operated
with the LLSV (liquid line solenoid valve) closed (de-energized) until the low-
pressure switch opens (low pressure condition, without giving alarm). When there
is a call to turn off a compressor the LLSV is closed. If the low suction pressure
switch (LPS) does not open within 60 seconds the LLSV is turned on than back off
(to try to unstuck the LLSV). The control waits another 60 seconds for the LPS to
open, this will happen 3 times. If, after 3 times, the low suction pressure switch
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