Carrier 69NT40-561-201 - Figure 3−8 Controller Operation - Frozen Mode

3−8T-364
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Controller Set Point at or BELOW −10°C (+14°F),
−.20°C
+.20°C
Air Circulation
Cooling,
Economized
Set Point
+2.5°C
(+4.5°F)
Frozen Mode
Falling
Temperature
Rising
Temperature
Figure 3−8 Controller Operation - Frozen Mode
3.3.15 Frozen “Heat” Mode
If the temperature drops 10C (18F) below set point,
the unit will transition to the frozen “heat” mode. The
evaporator 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.
3.3.16 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), com-
pressor motor (CH), economizer solenoid valve
(ESV), low speed evaporator fan motors (ES) ener-
gized and the blue COOL light illuminated. (See
Figure 3−9).
b. When the return air temperature decreases to a pre-
determined tolerance above set point, the green IN-
RANGE 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 blue
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 blue COOL is
illuminated.