Unit Description
32
When USDA sensors are installed, the controller
will automatically detect each sensor and activate
data logging. However, the USDA Type screen in
the Configuration menu must be set to the correct
sensor setting and each USDA sensor must be
calibrated to comply with USDA temperature
recording requirements.
Water-Cooled Condenser/Receiver
Tank
A water-cooled condenser/receiver provides the
unit with above deck and below deck operating
capabilities. Condenser fan control can be
provided by a C
ONDENSER FAN SELECTION
switch or a W
ATER PRESSURE switch.
The CONDENSER FAN switch is provided on the
control box with the water-cooled condenser
option. Place the C
ONDENSER FAN ON/OFF
switch in the W
ATER position for water-cooled
condenser operation.
The water pressure switch is installed in the water
inlet line. When water pressure greater than
117
± 21, 1.17 ± 0.21 bar, 17 ± 3 psig is provided
to the condenser-receiver tank, the water pressure
switch opens. This causes the controller to stop
the condenser fan.
Operating Modes
NOTE: See “MP-3000 Controller” chapter for
complete sequence of operation.
A sequence start of the required loads occurs
during initial start-up of the unit and when a
control mode shift requires the compressors to
start. As the controller relays and unit loads
energize, the controller LCD display shows the
setpoint temperature. The controller LED display
shows the controlling air sensor temperature. The
controlling sensor is determined by the setpoint
temperature:
The MP-3000 controller uses a
proportional-integral derivative (PID) algorithm
to provide accurate temperature control in direct
response to load demand. Therefore it is difficult
to predict which operating mode the unit should
be in by comparing the setpoint to the return or
supply air temperature. The unit operates in either
the Fresh (Chill) or Frozen mode. Chill to Frozen
mode transition point is -10 C (14 F).
Chill Loads: Controller Setpoint at
-9.9 C (14.1 F) or Above
Temperature control by the controller is based on
the supply air sensor temperature, the setpoint, the
modulation temperature range and the pull-down
rate. The evaporator fans operate in high speed
(except during defrost).
• Cool with Modulation (down to setpoint)
• Null (compressor and condenser fan stops,
evaporator fans operate)
• Heat (resistance heaters on, evaporator fans
operate)
• Defrost (resistance heaters on, evaporator fans
stop)
NOTE: If the Economy mode is set to On, the
evaporator fans operate on low speed at
setpoints of -9.9 C (14.1 F) and above
whenever the container temperature is
in-range.
Frozen Loads: Controller Setpoint
at -10 C (14 F) or Below
Temperature control by the controller is based on
the return air sensor temperature. The evaporator
fans operate continuously on low speed (except
during Defrost).
• Cool (down to 1 C [1.8 F] below setpoint)
• Null (compressor and condenser fan stops,
evaporator fans operate)
• Defrost (resistance heaters on, evaporator fans
stop)
NOTE: If the Economy mode is set to On, the
evaporator fans stop when the unit shifts to
Null. The controller automatically starts and
operates the evaporator fans on low speed for
5 minutes every 45 minutes while the unit
remains in Null.
Setpoint Controlling Sensor
-9.9 C (14.1 F) and above Supply Air Temperature
-10 C (14 F) and below Return Air Temperature
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