Frozen Mode Cooling - Sequence Of Operation; Frozen Mode - Economy; Figure 4.9 Frozen Mode - Carrier 69NT40-561-019 Operation And Service Manual

4.3.15

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 COOL light illuminated. (See
b. When the air temperature decreases to a predetermined tolerance above set point, the in-range light is illu-
minated.
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 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 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 cool light is illuminated.
The EEV and DUV are independently operated by the microprocessor. For full diagrams and legend,
see Section 8.
4.3.16

Frozen Mode - Economy

In order to activate economy frozen mode operation, a frozen set point temperature must be selected. The economy
mode is active when function code Cd34 is set to "ON". When economy mode frozen is active, the system will per-
form 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. After an off-cycle period of 60 min-
utes, 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 set point +0.2°C, the unit will restart the refrigeration system and
continue to cool until the previously mentioned off-cycle temperature criteria are met. If the control temperature is less
than the set point +0.2°C, the unit will turn off the evaporator fans and restart another 60 minute off-cycle.
T-359

Figure 4.9 Frozen Mode

ENERGIZED
DE- - ENERGIZED
ST
F
TC
HPS
IP- - CM TN
IP- - EM1 IP- - EM2
TH
HTT
ESV
TS
NOTE
4–10
24 VOLT POWER
CH
CF
TV ES
EF
TE EF
HR
Figure 4.9).