Perishable Mode - Trim Heat; Frozen Mode - Temperature Control; Frozen Steady State; Frozen Idle Mode - Carrier PrimeLINE 69NT40-561-200 Operation And Service Manual

4.3.13

Perishable Mode - Trim Heat

If the system capacity has been decreased to the lowest allowable capacity and conditions exist that warrant max-
imum temperature stability the controller will pulse the HR relay to energize the evaporator heaters in sequence
with the compressor digital signal.
4.3.14

Frozen Mode - Temperature Control

In Frozen mode, the controller maintains the return air temperature at setpoint, the yellow RETURN indicator light is
illuminated, and the default reading on the display window is the return temperature sensor (RTS) reading.
When the return air temperature enters the in-range temperature tolerance (Cd30), the green IN-RANGE light will
energize.
When CnF26 (Heat Lockout Temperature) is set to -10°C, frozen mode is active with setpoints below -10°C
(+14°F). When CnF26 is set to -5°C, frozen mode is active with setpoints below -5°C (+23°F).
When the system is in Frozen mode, the highest priority is given to bringing the container down to setpoint, the sys-
tem will remain in economized operation.
4.3.15

Frozen Steady State

Frozen cargos are not sensitive to minor temperature changes, and the frozen temperature control system takes
advantage of this to greatly improve the energy efficiency of the unit. Frozen range temperature control is accom-
plished by cycling the compressor on and off as the load demand requires.
Once the frozen setpoint is reached, the unit will transition to frozen steady state (economized operation).
4.3.16

Frozen Idle Mode

When temperature drops to setpoint minus 0.2°C (0.4°F) and the compressor has run for at least five minutes, the
unit will transition to the Frozen Idle mode. The compressor is turned off and the evaporator fans continue to run to
circulate air throughout the container. If temperature rises above setpoint +0.2°C, (0.4°F) the unit will transition back
to the frozen steady state mode.

Figure 4.8 Controller Operation - Frozen Mode

Frozen Mode
Controller Set Point at or BELOW 10 C (+14 F),
or 5 C (+23 F) optionally
Cooling,
Economized
.20 C
Air Circulation
Falling
Temperature
+2.5 C
(+4.5 F)
+.20 C
Set Point
Rising
Temperature
4–9 T-362