General Description

The CRR DF unit uses a basic cascade refrigeration system to achieve to frozen and deep frozen cargo temperatures between -10 C and -70 C (+14 F and -94 F). (-70 C is the Lowest possible set-point provided the Box Size is set to 10´ or 20´, -65C would be lowest possible set-point for Box Size of 40´). The CRR DF cascade refrigeration system design allows shippers to economically carry cargo at deep frozen temperatures using proven, reliable transport refrigeration system technology.

The CRR DF cascade systems consists of two separate, single-stage refrigeration systems with different refrigerants. One system is a low temperature stage system that uses a hermetic scroll compressor and R-23 refrigerant. The evaporator of the low temperature stage system cools the cargo air, achieving cargo temperatures down to -70 C (-76 F). (-70 C is the Lowest possible set-point provided the Box Size is set to 10´ or 20´, -65C would be lowest possible set-point for Box Size of 40´).

The second system is a high temperature stage system that uses a semi-hermetic reciprocating compressor and R-134a refrigerant. The evaporator of the high temperature stage system cools the condenser of the low temperature stage system through a special plate heat exchanger. The condenser of the high temperature stage system then transfers the cargo heat to the ambient air.

MP3000/MP3000a controller incorporates refrigeration system component control, thermostat, digital thermometer and fault indication capabilities into one self-contained package. Units with a MP3000/MP3000a controller are also equipped with a separate datalogger

Each controller mounts in a weather tight, corrosion resistance enclosure. A large-character LED display (top) provides easy viewing of the control sensor temperature (return or supply air temperature). A 4-line, 20-character LCD display (bottom) display shows important data including the setpoint temperature, controller Main Menu tree and important unit operating data.

Sixteen general purpose keys are used to enter and scroll through the controller menu tree and message text; initiate Pretrip and Function tests; enter new setpoint temperature; and enter trip information. The keyboard supports both numerical and text input. Four special keys provide quick access to setpoint temperature change, manual defrost initiation, alternate return/supply air temperature display, and alternate temperature scale (C/F) display.

Each control system consists of a MP3000/MP3000a microprocessor controller, a main relay printed circuit board and six temperature sensors.

Status indicator LEDs in the LED display signal Compressor, Defrost, Heat, In-range, Alarm, Supply Temperature display and Return Temperature display.

Units with a MP3000/MP3000a controller are also equipped with a separate datalogger. The datalogger can record sensor temperatures as well as loss of power, alarms, unit operating modes, sensor failure, setpoint change and unit shutdown indications. MP3000/MP3000a data recordings are stored in a RAM memory that is backed by battery.

Logging intervals are selectable from 1 minute and 1/2, 1, 2 or 4 hours. When a 1 hour logging interval is selected, the datalogger memory can store approximately 512 days of information. The logging of USDA sensors is fixed at 1 hour intervals to comply with USDA requirements.

The datalogger clock is factory set at UTC time. All data logs include the time and date; setpoint temperature; and supply, return, USDA1, USDA2 and USDA3 sensor temperatures. All temperature logs can be viewed from the controller’s LCD message display.

A high speed serial communication port provides data retrieval using a DRU-II or SmartSponge handheld data retriever; or a REFCON power line remote monitoring system.

Three evaporator fans operate continuously to circulate air inside the container. Two-speed fans operate continuously on low speed for deep frozen and frozen cargo (setpoints of -10 C [+14 F] and below).

The datalogger includes provisions for the use of three USDA sensors. These sensors allow temperatures in various areas of the load to be monitored and recorded for United States Department of Agriculture use in monitoring Cold Treatment shipments. The USDA sensors record temperatures from -80.0 C to +10 C (-112.0 F to +50.0 F).

A REFCON remote monitoring modem is provided to permit remote monitoring via the power cable. High speed transmission reads all controller information. Data can also be retrieved from the datalogger via high speed transmission.