Carrier 69NT40-561-019, Operation And Service Manual

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4–9 T-359
4.3.12 Frozen Mode - Temperature Control
When in the frozen mode, the controller maintains the return air temperature at or below set point, the RETURN
indicator light will be illuminated on the display module and the default reading on the display window will be the
return air probe reading.
When the return air temperature enters the in-range temperature tolerance as selected at function code Cd30, the
in-range light will energize.
Figure 4.8 Controller Operation - Frozen Mode
4.3.13 Frozen Mode - Standard
Frozen range cargos are not sensitive to minor temperature changes. The method of temperature control
employed in this range takes advantage of this to greatly improve the energy efficiency of the unit. Temperature
control in the frozen range is accomplished by cycling the compressor on and off as the load demand requires.
When temperature drops to set point minus 0.2°C 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, the unit will transition back to the frozen
mode cooling.
4.3.14 Frozen Mode - Heat Lockout Temperature
With configuration variable CnF26 (Heat Lockout Temperature) set to -10°C the frozen mode of operation is active
with set points
at or below -10 ° C (+14 °F). With the variable set to -5°C, the frozen mode is active at or below -5°C
(+23°F).
If the temperature drops 10°C below set point, the unit will transition to the frozen “heating” mode, in which the
evaporator fans are brought to high speed. The unit will transition back to the frozen mode cooling when the tem-
perature rises back to the transition point.
SET POINT
FALLING
TEMPERATURE
--0.2
_
C
+0.2
_
C
NOTE: TEMPERATURES INDICATIONS ARE ABOVE OR BELOW SET POINT
AIR CIRCULATION
ECONOMIZED
COOLING
SET POINT
RISING
TEMPERATURE