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4.5.3.5 Compartment temperature has exceeded the Override Functional Parameter value
During MINIMUM OFF TIME the control system continually monitors the refrigerated compartment tem-
perature and the override functional parameter value. During the Minimum Off Time, if the refrigerated
compartment temperature drifts this far above or below setpoint in the Perishable Range, or above set-
point in the Frozen Range, the unit will override the Minimum Off Time, and restart. The value may be set
from 3.6 to 18°F (2 to 10°C) in 0.5 increments. The factory default setting is 12°F (6.7°C).
Whenever the unit restarts, temperature control will be in the Pulldown or Pull-Up mode.
4.5.4 Continuous Operation
In Continuous Operation, the unit will not shutdown except in response to a shutdown alarm. Temperature control
in the compartment will operate under Pulldown, Pull-Up, Cooling, Heating and Null.
Continuous Operation is normally used for fresh produce and other sensitive product loads. The Start-Stop/ Con-
tinuous key is pressed to switch between Continuous Operation and Start-Stop Operation. The mode of operation
will be indicated in the status bar.
NOTE
The control system may be locked so that the unit will always operate in Start-Stop or in Continuous
whenever the setpoint is within a specific range. Refer to Range Lock (Section 4.9.2) for additional
information.
4.6 Temperature Control
4.6.1 Perishable And Frozen Setpoint Ranges
There are two ranges defined for setpoint.
1. Perishable Range = setpoints above +10.4°F (-12°C).
2. Frozen Range = setpoints at or below +10.4°F (-12°C).
4.6.2 Temperature Determination
The APX Control System monitors the temperature readings from the supply and return temperature sensors to
determine the mode of operation required to maintain compartment temperature in accordance with setpoint.
The sensor used for temperature control is dependent on the selection made in the TEMP CONTROL Functional
Parameter.
• If the selection is RETURN AIR the return air sensor (RAT) will be used for any setpoint.
• If the selection is SUPPLY AIR the control system will switch to the supply air sensor (SAT) when operating
with a perishable setpoint (refer to Section 4.6.1 for more information on frozen and perishable setpoints)
and the return air sensor will continue to be used for frozen setpoints.
The modes of operation include Pulldown, Pull-Up, Cooling, Heating and Null.
4.6.3 Cool/Heat/Null Mode Switching Logic
When not in Pulldown and in Continuous Run mode, operation in cool, heat and null modes is determined in accor-
dance with the calculated Controlling Temperature value (CT), the difference between this value and Setpoint (SP)
and the FUEL SAVER (ECO) MODE Functional Parameter setting in accordance with the following:
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