62-11785 4–2
4.3 OPERATION
The APX Control System will energize the condenser fan motors in order to determine the phase sequence of the
incoming power. If incoming power is not correct, the system will shutdown and restart, energizing the other power
supply contactor (PSCON or PSCON2). If the phase sequence is not corrected by this action, the A00074 -
“PHASE REVERSED” alarm will be activated and the unit will shutdown.
Once the power selection is made:
• the stepper valve module will open the compressor suction modulating valve (CSMV), evaporator expansion
valve (EVXV) and economizer expansion valve (ECXV), to equalize system pressure, and then bring the
valves to a predetermined position before the unit starts.
• the contactor control boards will energize the compressor, condenser fan motors, evaporator fan motor and/
or electric heaters as required.
4.3.1 Soft Start (Bump Start)
On command to start the compressor the control system will determine if there is a need to perform a Soft Start.
Soft Start is performed to clear refrigerant from the compressor and/or return oil; Soft Start will be activated if:
• the compressor has been off for more than twenty- four hours or
• the compressor has been off for more than two hours and suction and discharge pressure are within 10 psig
(0.7 bar) or
• the compressor has been off for more than two hours and suction pressure is above discharge pressure
During Soft Start the control system will de-energize the liquid injection valve (LIV), economizer expansion valve
(ECSV) and energize the buzzer for five seconds. Then the compressor will operate for one second on, followed by
nine seconds off. The on/off sequence may repeat up to four additional times.
Following Soft Start the compressor will transition to steady state operation, and the evaporator fans will start.
If Soft Start is not required, the buzzer will be energized for five seconds the compressor will start and the evapora-
tor fans will start.
The unit will not restart for at least 30 seconds following a shutdown.
4.3.2 Start-Up
On command to perform a Start-Up, the control system will energize the buzzer for five seconds. The refrigeration
system or heaters will then operate in the mode(s) required for temperature control.
4.4 START-STOP OPERATION
Start-Stop is provided to reduce power consumption. This feature allows full automatic control of the unit by moni-
toring compartment temperature and battery condition.
The main function of Start-Stop Operation is to shutdown the unit after certain conditions are met (to provide an effi-
cient temperature control system) and to initiate a restart sequence after certain conditions are met. The Start-Stop/
Continuous key is pressed to select between Continuous and Start-Stop Operation. The mode of operation will be
indicated in the status bar.
The control system may be locked so that the unit will always operate in Start-Stop whenever the set-
point is within a specific range. Refer to Range Lock (Section 4.8.2) for additional information.
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