MP-3000 Controller
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log interval in which a Defrost cycle is
pending or active (i.e. both the 8:00 and 9:00
data logs on 1 hour logging interval).
• On Chill Loads (setpoints at -9.9 C [14.1 F]
and above), the initial time interval is:
• 8 hours of compressor operation at supply
air temperatures of 5.1 C (41.2 F) or
above.
• 2.5 hours of compressor operation at
supply air temperatures of 5.0 C (41.0 F)
or below. One-half (0.5) hour is added to
the time interval each timed defrost
interval. Defrost synchronization creates
step intervals of 3, 4, 4, 5, 5, 6, 6 and 7
hours. Maximum time interval is 7 hours.
• On Frozen Loads, the initial time interval is 8
hours. Two (2) hours are added to the time
interval each timed defrost interval. Maximum
accumulated time interval is 24 hours.
• Defrost timer resets if the unit is off more than
12 hours, setpoint is changed more than 5 C
(8.9 F) or PTI (pre-trip) test occurs.
NOTE: If unit operating conditions do not
allow the unit to enter a defrost cycle,
“Defrost Not Activated” appears on LCD
display when the D
EFROST key is pressed.
When the Defrost mode is initiated:
• The controller stops the compressor,
condenser fan and evaporator fans.
• When the compressor stops, the controller
turns on the Defrost LED, Heat LED and
energizes the heater contactor, turning on the
electric heaters.
The controller terminates the Defrost
mode when:
• Evaporator temperature:
• Chill mode: Evaporator coil sensor
temperature reaches 30 C (86 F); or
exceeds 18 C (65 F) for 35 minutes.
• Frozen mode: Evaporator coil sensor
temperature reaches 30 C (86 F); or
exceeds 8 C (46 F) for 35 minutes.
• Interval timer: Controller terminates defrost
after 90 minutes on 60 Hz power (120 on
50 Hz power). Alarm code 20 will be
generated if this occurs.
• Power off: Turning U
NIT ON/OFF switch OFF
terminates defrost.
When the defrost mode is terminated:
• The Heat and Defrost LEDs turn off and the
heater contactor is de-energized. The
controller starts the compressor to pre-cool the
evaporator coil. The condenser fan starts if
required.
• The controller pre-cools the evaporator coil to
the supply air temperature (or for 3 minutes
maximum) to minimize heat energy release
into the container. The liquid injection valve is
energized if the modulation capacity is 91% or
less. The controller then starts the evaporator
fans.
Changing the Setpoint
NOTE: Humidity control, humidity
setpoint and Economy mode can also
be set from the Setpoint menu. See “Setpoint
Menu” under “Menu Operating Instructions” in
this chapter.
To change the controller setpoint, turn the U
NIT
O
N/OFF switch ON. With the standard LCD
message display showing on the controller
(i.e. setpoint temperature):
1. Press the S
ETPOINT key. The Setpoint menu
appears with the cursor in the “TEMP SETP”
line.
2. Press the F4 key. An Enter Arrow appears in
the menu line and the current setpoint
disappears.
3. Enter (type) the new setpoint in the LCD
display using the general purpose keypad. To
enter a minus setpoint, press the E
XIT (±) key
first. The cursor moves to the right of the
screen as each key entry is acknowledged and
displayed.
NOTE: Always check that the setpoint
entered in the LCD display is correct before
proceeding.
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