Basic Unit Controls, Instruments and Protection Devices

ON/OFF Switch: ON position. Unit will operate on cool or null depending on the controller setpoint temperature and the container air temperature. OFF position. The unit will not operate.

Control System Circuit Breaker: A 7 ampere manual reset circuit breaker protects the control circuit. This circuit breaker is located in the control box beside the On/Off switch.

Main Circuit Breaker: A 32 ampere manual reset circuit breaker protects the 460/380V power supply circuit to the unit electric motors and control system transformer. The main power circuit breaker is located in the control box.

Fuses: A number of fuses are located on the main relay board and controller plug to protect unit circuits and components.

• Three 20 amp fuses protect high voltage circuits on the main relay board.

• A 2 amp fuse protects the controller’s 28 V system.

• A 2 amp fuse protects the controller’s battery charging circuit.

Overload Protection: The condenser fan motor, evaporator fan motors and compressor motors include internal overload protection with automatic reset.

Phase Sequence Selection: When the On/Off switch is turned ON, phase sensors on the main relay board determine the incoming power phase to ensure proper condenser fan, evaporator fan and compressor rotation.

A MP3000/MP3000a microprocessor controls all unit functions to maintain the cargo at the proper temperature. The controller also monitors and records system faults and performs pre-trip.

Keypad: Sixteen general purpose keys are used to display information, change the setpoint, change programmable features and initiate control tasks.

°C–°F Key: Press this key to view temperatures in the LED display in the alternate temperature value. Alternate value (C or F) shows while the key is pressed

. RET/SUP Key: Press this key to view the alternate sensor temperature in the LED display. Alternate sensor (return or supply) shows while the key is pressed.

Defrost Key: Press this key to initiate a manual defrost cycle. If the evaporator coil temperature is below 10 C (50 F), the unit will defrost. Otherwise the controller will display “Defrost Not Activated” in the LCD display and the unit will continue normal operation.

Setpoint Key: Press this key to change the setpoint. Cursor in the LCD display automatically appears in the “TEMP SETP” line of the Data menu. See “Changing the Setpoint” in the Microprocessor Controller chapter for complete instructions.

Status Indicator LEDs: located in the large LED display signal:

• Supply (Air Temperature)

• Return (Air Temperature)

• Humidity Mode (Inactive on CRR DF units)

• Compressor (Cooling On)

• Heat (On during defrost)

• Defrost

• In-Range (Temperature)

• Alarm

The In-range LED illuminates when the controlling air sensor temperature is less than 3.0 C (5.4 F) above setpoint (standard). The controller maintains the in-range signal during defrost and after defrost for 60 minutes.

LED Display: Large red LED display shows current control temperature during normal operation. LED display also shows current test state during a Pretrip (PTI) or Function test.

LCD Display: A 4-line LCD message display shows setpoint during normal operation. LCD display also shows controller menu and unit operation information when special keys are pressed.