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Electrical Maintenance
98
Condenser Fan
Check for proper condenser fan rotation by placing a small cloth or sheet of paper against the condenser
fan grille on the front of the unit. Proper rotation will blow the cloth or paper away from the grille.
Improper rotation will hold the cloth or paper against the grille.
If the condenser fan is rotating backwards, refer to the unit wiring diagram to correct fan motor wiring at
the fan motor junction box or condenser fan contactor. To correct improper fan rotation, reverse any two
fan power cord leads at the condenser fan contactor (disconnect power supply before reversing leads). DO
NOT move the CH ground wire.
Evaporator Fans
Visually inspect the evaporator fan blades for proper rotation. Arrows located on the underside of the fan
deck indicate the correct direction of rotation.
If an evaporator fans rotate backwards, refer to the unit wiring diagram to correct motor wiring at the fan
motor junction box or evaporator fan contactor (disconnect power supply before reversing leads). (DO
NOT move the ground wire which is labeled CH.)
Electric Heaters
Twelve electric heater elements are located underneath the evaporator coil. If a heater element is
suspected of malfunctioning, inspect the connections:
•
If the connections appear correct and secure, isolate and check the resistance of each individual heater
element by disconnecting it from the circuit.
•
Check resistance with an ohmmeter.
NOTE: When repairing heater connections, protect the new connections from the ingress of moisture
with heat shrink tubing. All heaters should be secured to prevent contact with sharp metal edges.
Low Pressure Cutout Switch (R-23 System on CRR DF MPC2000ID
Units Only)
A low pressure cutout switch is located on the R-23 compressor suction line. If the R-23 suction pressure
becomes too low, the switch opens to stop both compressors:
•
LCD Display Message: R-23 Low Pressure Cutout.
•
Evaporator and condenser fans continue normal operation.
•
R-134a compressor will restart if the low refrigerant condition is corrected (switch closes) as long as
power is available. The low pressure switch resets (closes) when the pressure increases to 70 ± 20
kPa, 0.7 ± 0.2 bar, 10 ± 3 psig.
•
When R-23 low pressure switch resets, R-23 compressor restarts 30 seconds after R-134a compressor
restarts.
Summary of Contents for Thermo King CRR DF MPC2000
Page 5: ...4 ...
Page 11: ...List of Figures 10 ...
Page 13: ...Introduction 12 ...
Page 19: ...Safety Precautions 18 ...
Page 21: ...Service Guide 20 ...
Page 47: ...Unit Description 46 ...
Page 97: ...Microprocessor Controller 96 ...
Page 101: ...Electrical Maintenance 100 ...
Page 141: ...Structural Accessory Maintenance 140 ...
Page 147: ...Refrigeration System Diagnosis 146 ...
Page 150: ...149 CRR DF MPC2000 Controller Diagram ...
Page 151: ...150 CRR DF MPC2000 Main Relay Board Electrical Diagram ...
Page 152: ...151 CRR DF MPC2000 Unit Wiring Schematic Low Speed Winding ...
Page 153: ...152 CRR DF MP3000A Controller Diagram ...
Page 154: ...153 CRR DF MP3000A Main Relay Board Electrical Diagram ...
Page 155: ...154 CRR DF MP3000A Unit Wiring Schematic Low Speed Winding ...
Page 157: ...156 CRR DF Refrigeration System Components Page 2 of 2 ...
Page 161: ...160 CRR DF Full Cool Flow and Pressure Diagram Page 2 of 2 ...
Page 163: ...162 CRR DR Evacuation Station and Unit Connections Page 2 of 2 ...