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

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4–11 T-365
4.3.18 Frozen Economy Mode
In order to activate Frozen Economy Mode, a frozen set point temperature must be selected, and Cd34 (Economy
Mode) set to “ON.” When economy mode is active, the system will perform normal frozen mode operations except
that the entire refrigeration system, excluding the controller, will be turned off when the control temperature is less
than or equal to the set point -2°C (4°F).
After an off-cycle period of 60 minutes, the unit will turn on high speed evaporator fans for three minutes, and then
check the control temperature. If the control temperature is greater than or equal to the frozen set point +0.2°C
(0.4°F), the unit will restart the refrigeration system and continue to cool until the off-cycle temperature criteria are
met. If the control temperature is less than the frozen set point +0.2°C (0.4°F) the unit will turn off the evaporator
fans and restart another 60 minute off-cycle.
4.3.19 Frozen Mode Cooling - Sequence of Operation
a. When the return air temperature is above set point and decreasing, the unit will transition to economized
cooling with the condenser fan motor (CF), compressor motor (CH), economizer solenoid valve (ESV), low
speed evaporator fan motors (ES) energized and the white COOL light illuminated. (See
Figure 4.9 ).
b. When the return air temperature decreases to a predetermined tolerance above set point, the green
INRANGE light is illuminated.
c. When the return air temperature decreases to 0.2°C (0.4°F) below set point, contacts TC, TS and TN are
opened to de-energize the compressor, economizer solenoid valve and condenser fan motor. The white
COOL light is also de-energized. The EEV will close.
d. The evaporator fan motors continue to run in low speed to circulate air throughout the container. The green
IN-RANGE light remains illuminated as long as the return air is within tolerance of set point.
e. If return air temperature drops to 10°C (18°F) or more below set point, the evaporator fans increase to high
speed.
f. When the return air temperature increases to 0.2°C (0.4°F) above set point and three minutes have elapsed,
the EEV opens and contacts TC, TS and TN close to restart the compressor, open the ESV and restart the
condenser fan motor. The white COOL is illuminated.
Figure 4.9 Frozen Mode
NOTICE
The EEV and DUV are independently operated by the microprocessor. Complete schematics
and legends are located in
Section 8 .
ENERGIZED
DE-ENERGIZED
24 VOLT POWER
TG
ST
F
HPS
CH
IP-CM
TC
CF
TE
IP-EM1
EF
IP-EM2
HTT
TH HR
ESV
TS
TV EF ES
TN
FS
LC
TG CF FS
LC