Ingersoll-Rand Thermo King CRR DF MPC2000, Maintenance Manual

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Microprocessor Controller
63
Continuous Temperature Control Operation
Frozen Loads — Controller Setpoint at -10 C (14 F) and Below
The controller regulates compressor operation based the return air sensor and setpoint temperatures to
determine operating mode switch points. The controller operates the unit on:
• Cool mode
• Null mode
• Defrost mode
• Evaporator fans operate on low speed to continuously circulate air inside the container (except during
defrost).
• Controller LED display shows the return air sensor temperature.
• Controller LCD display shows the setpoint.
Cool
• After initial start-up and pull-down to 1.0 C (1.8 F) below setpoint, the controller calls for the Cool
mode whenever the return air temperature increases more than 1.0 C (1.8 F) above setpoint.
• Unit operates in Cool mode for a minimum of 15 minutes to prevent rapid cycling between Cool and
Null.
• After initial pull-down to setpoint, the controller keeps the In-range LED ON as long as the return air
temperature remains less than 1.5 C (2.7 F) above setpoint.
Null
• The controller calls for Null when the Return Air Temperature decreases more than 1.0 C (1.8 F)
below setpoint.
• The controller de-energizes the compressor contactors and condenser fan contactor, stopping the both
compressors and the condenser fan.
• Units remains in Null mode for a minimum of 10 minutes to prevent rapid cycling between Cool and
Null.
• The evaporator fans continue to operate in low speed.
Defrost
During the Cool or Null modes, the controller initiates the Defrost mode when the evaporator coil sensor
temperature is below 18 C (65 F) and:
• Demand defrost function determines that defrost is required when the temperature difference between
the return air sensor and setpoint increases to a preset value and a minimum of 6 hours of compressor
ON (running) time have elapsed since the previous defrost.
• A manual defrost is initiated by pressing the Defrost special function key or by Refcon Remote
Monitoring Modem (RMM).
NOTE: If unit operating conditions do not allow the unit to enter a defrost cycle, “Defrost Not
Activated” appears on LCD display when the DEFROST key is pressed.