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MP-3000a Controller
60
•
Supply air sensor control algorithm increases
temperature control accuracy and protection
against frost damage (see “Chill Loads” under
General Theory of Operation in this chapter).
•
Controller pulses electric heaters ON and OFF
for additional frost protection if the return air
temperature decreases to within 0.3 C (0.5 F)
of setpoint (see “Chill Loads” under General
Theory of Operation in this chapter).
•
Controller turns ON the Heat LED whenever
the heaters are pulsed ON and OFF.
Heat
•
If the supply air temperature is too low and the
calculated KVQ valve setting is above the
setpoint, the controller stops the compressor,
de-energizes the liquid line solenoid and
pulses the electric heaters ON for 2 to 60
seconds every 60 seconds to provide heat. The
amount of ON time depends on the amount of
heat required to gradually increase the supply
air temperature to setpoint.
Frozen Loads — Controller Setpoint
at -10 C (14 F) and Below
At setpoints of -10 C (14 F) and below, the
controller locks out the Modulation and Heat
modes. The controller regulates compressor
operation based the return air sensor and setpoint
temperatures.
At setpoints of -10 C (14 F) and below, the
controller operates the unit on:
•
Cool mode
•
Null mode
•
Defrost mode (electric heaters On, evaporator
fans Off)
•
Evaporator fans operate on low speed and
continuously circulate air inside the container
(except during defrost; or when Economy
mode is ON and the unit is in Null mode)
•
Controller LED display shows the return air
sensor temperature.
•
Controller LCD display shows the setpoint
temperature.
A.
Cool with Modulation* (control temperature
differential is above setpoint)
B.
Heat (electric heaters pulse ON and OFF on a
60 second duty cycle if the return air
temperature decreases to 0.3 C [0.5 F] above
setpoint; or the supply air temperature is too
low)
C.
In-Range (bases on supply air temperature)
1.
Decreasing Temperature
2.
Setpoint
3.
Increasing Temperature
* If the compressor stops, it must remain OFF for a
minimum of 5 minutes.
Figure 14: Chill Load Sequence (Setpoints at -9.9C
[14.1 F] and Above)
AJA1414
Summary of Contents for CRR-40 119
Page 4: ......
Page 16: ...Safety Precautions 16...
Page 18: ...Service Guide 18...
Page 20: ...Model Features 20...
Page 32: ...Specifications 32...
Page 120: ...MP 3000a Controller 120...
Page 160: ...Wiring and Schematic Diagrams Index 160...
Page 161: ...161 MPC2000 Wiring Schematic...
Page 162: ...162 MPC2000 High Voltage Wiring Diagram...
Page 163: ...163 MPC2000 Low Voltage Wiring Diagram...
Page 164: ...164 MPC2000 WCC Wiring Schematic...