Perishable Pulldown; Perishable Steady State; Perishable Idle, Air Circulation; Perishable Heating - Carrier PrimeLINE 69NT40-561-200 Operation And Service Manual

4.3.4

Perishable Pulldown

When the system is in Perishable Pulldown mode, the highest priority is given to bringing the container down to
setpoint. When cooling from a temperature that is more than 2.5°C (4.5°F) above setpoint, the system will be in
Perishable Pulldown mode in economized operation. However, pressure and current limit functions may restrict the
valve if either exceeds the preset value.
4.3.5

Perishable Steady State

In Perishable Steady State mode, the control temperature is maintained near a setpoint that is above the heat lock-
out temperature. Once setpoint is reached, the unit will transition to Perishable Steady State mode. This results in
unloaded operation by cycling the DUV to limit capacity and maintain steady temperature control.
The unit is capable of maintaining supply air temperature to within +/- 0.2°C (+/- 0.36°F) of setpoint. Supply air tem-
perature is controlled by positioning of the electronic expansion valve (EEV), cycling of the digital unloader valve
(DUV), cycling of the compressor, and cycling of the heaters.
4.3.6

Perishable Idle, Air Circulation

When it is unnecessary to run the compressor to maintain control temperature, the system enters Perishable Idle
mode. If the controller has determined that cooling is not required or the controller logic determines suction pres-
sure is at the low pressure limit, the unit will transition to Perishable Idle mode. During Perishable Idle mode, the
compressor is turned off, but the evaporator fans continue to run to circulate air throughout the container. If tem-
perature rises +0.2°C (0.4°F) above setpoint, the unit will transition back to Perishable Steady State mode.
4.3.7

Perishable Heating

When it is necessary to raise the control temperature, the system will enter Perishable Heating mode. If the tem-
perature drops to 0.5°C (0.9°F) below setpoint, the unit will transition to Perishable Heating mode, and the heaters
will be energized. The unit will transition back to Perishable Idle mode when the temperature rises to 0.2°C (0.4°F)
below the setpoint, and the heaters will de-energize.
Perishable Mode
Controller Set Point ABOVE -10 C (+14 F),
or -5 C (+23 F) optionally
Set
Point
-0.50 C
Falling
Temperature

Figure 4.5 Controller Operation - Perishable Mode

Cooling,
Unloaded
+0.20 C
Air Circulation
-0.25 C
Heating
Rising
Temperature
Pull Down
(Only Applicable to Perishable Mode)
Controller Set Point ABOVE -10 C (+14 F),
or -5 C (+23 F) optionally
Cooling,
Enconomized
Cooling,
Unloaded
-0.20 C
Air Circulation
Air Circulation
-0.50 C
Heating
4–5
+2.5 C
(+4.5 F)
Set
Point
-0.20 C
T-362