MP-3000a Controller
58
The Economy Mode also modifies the
temperature control algorithm on frozen loads to
extend the Null mode. The unit continues on Cool
operation until return air temperature reaches
ECMIN temperature. Default ECMIN setting is
2.0 C (3.6 F) below setpoint. ECMIN temperature
is adjustable from 0 to 5 C (0 to 8.9 F) below
setpoint through the Configuration menu of the
controller.
The unit remains in Null until the return air
temperature increases to ECMAX temperature at
the expiration of a 45 minute Null state time
sequence. Default ECMAX setting is.2 C (0.4 F)
above setpoint. ECMAX setting is adjustable
from 0 to 5 C (0 to 8.9 F) above setpoint through
the Configuration menu of the controller.
NOTE: On Frozen loads, supply and return air
temperatures may vary considerably during
Economy mode operation due to long periods of
no air circulation.
Probe Test
The controller constantly monitors the left hand
and right hand supply sensors, return sensor and
defrost (evaporator coil) sensor to determine when
to initiate a demand defrost. If a demand defrost is
requested and defrost has occurred within last 90
minutes, the controller initiates a Probe Test to
check for a defective sensor.
During a Probe Test, the LCD display shows
“Probe Test Please Wait”. The controller operates
the unit on high speed evaporator fans only for 5
minutes. All sensor temperatures are then
compared:
•
Sensors with large temperature differences
are discarded from the control algorithm.
The controller then activates the
appropriate Alarm codes to identify the
defective sensor(s).
•
If no sensors are found defective,
controller LCD display shows “Running
with High Supply Difference” message.
Sensor errors recorded during a Probe Test
are cleared when the next Defrost is
initiated or Unit On/Off switch is turned
OFF.
NOTE: A manual Probe Test can be performed
by a technician by selecting Sensor Check from
the Manual Test Function menu.
Dehumidify Mode (Option)
During Chill mode operation, a dehumidification
system is available to reduce the relative humidity
in the container to the desired humidity setpoint.
The Dehumidify Mode option is turned on from
Setpoint menu of the controller. The relative
humidity setpoint can be set from 60 to 95% from
the Setpoint menu too.
The use of the Dehumidify Mode should be
established by the shipper. When the Dehumidify
Mode is ON, the controller:
a. Energizes (closes) the dehumidify valve
when the humidity level is 2% or more
above setpoint; and the KVQ valve has
reduced the unit cooling capacity by about
25%. This reduces the size of the
evaporator providing cooling by 50%,
causing the coil to become colder and
condense more moisture from the
container air.
b. Pulses the electric heaters ON and OFF
when the humidity level is 5% or more
above setpoint; and the KVQ valve has
reduced the unit cooling capacity by about
50% (40% at setpoint temperatures below
5 C [41 F]). This increases the cooling
load on the evaporator coil, thereby
causing the coil to become even colder and
condensing more moisture from the
container air.
Sequence Of Operation
Unit Start-up
A 60 second sequence start of the required loads
occurs during initial start-up of the controller. If
cooling (or heating) is required, the unit operates
in the cool (or heat) mode.
•
When the unit On/Off switch is turned ON,
the LED display turns On and then Off.
•
The setpoint appears briefly in the LED
display.
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...