Carrier 69NT40-561-300, Operation And Service Manual

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T-365 4–10
When CnF26 (Heat Lockout Temperature) is set to -10°C, frozen mode is active with set points below -10°C
(+14°F) . When CnF26 is set to -5°C, frozen mode is active with set points below -5°C (+23°F) .
When the system is in Frozen Mode, the highest priority is given to bringing the container down to set point, the
system 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.
4.3.16 Frozen Idle Mode
When temperature drops to set point 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 set point +0.2°C, (0.4°F) the unit will transition
back to the frozen steady state mode.
Figure 4.8 Controller Operation - Frozen Mode
4.3.17 Frozen “Heat” Mode
If the temperature drops 10°C (18°F) below set point, the unit will transition to the frozen “heating” mode. The evap-
orator fans are brought to high speed, and the heat from the fans is circulated through the container. The unit will
transition back to frozen steady state when the temperature rises back to the transition point.
Controller Set Point at or BELOW
ï
10
q
C (+14
q
F),
or
ï
5
q
C (+23
q
F) optionally
ï
.20
q
C
+.20
q
C
Air Circulation
Cooling,
Economized
Set Point
+2.5
q
C
(+4.5
q
F)
Frozen Mode
Falling
Temperature
Rising
Temperature