Carrier 69NT40-561-201, Руководство по эксплуатации и обслуживанию, Страница: 34 / 117

3 − 5 T-364
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Controller Set Point ABOVE − 10 ° C (+14 ° F)
− .20
°
C
− .50 ° C
+.20 ° C
− .20
°
C Air Circulation
Heating
Cooling,
Unloaded
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ÍÍÍÍÍÍÍÍÍÍ
Controller Set Point ABOVE − 10 ° C (+14 ° F)
− .20
°
C
− .50 ° C
− .20 ° C
Air Circulation
Heating
Cooling,
Economized
Pull Down
+2.5 ° C
(+4.5 ° F)
Cooling,
Unloaded
Falling
Temperature
Rising
Temperature
Perishable Mode
(Only Applicable to Perishable Mode)
Set
Point
Figure 3 − 5 Controller Operation - Perishable Mode
3.3.8 Perishable Dehumidification
Dehumidification is provided to reduce the humidity
levels inside the container. Dehumidification is activated
when a humidity value is set at Cd33. The yellow
SUPPLY LED will flash ON and OFF every second to
indicate that dehumidification is active. Once
dehumidification is active and the following conditions
are satisfied, the controller will activate the heat relay to
begin dehumidification.
1. The humidity sensor reading is above the humidity
set point (Cd33).
2. The unit is in perishable steady state and supply air
temperature is less than 0.25 C (0.45 F) above set
point.
3. The heater debounce timer (three minutes) has
timed out.
4. Heater termination thermostat (HTT) is closed.
If the above conditions are true for at least one hour the
evaporator fans will switch from high speed to low
speed. Evaporator fan speed will then switch every
hour, as long as the 4 conditions are met.
If any condition except item (1) becomes false OR if the
relative humidity sensed is 2% below the dehumidifica-
tion set point, the high speed evaporator fans will be
energized.
During dehumidification power is applied to the defrost
heaters. This added heat load causes the controller to
open the EEV to match the increased heat load while
still holding the supply air temperature very close to the
set point.
Opening the EEV reduces the temperature of the
evaporator coil surface, which increases the rate at
which water is condensed and removes water from the
passing air. Removing water from the air reduces the
relative humidity. When the relative humidity sensed is
2% below set point, the controller de-energizes the heat
relay. The controller will continue to cycle heating to
maintain relative humidity below the selected set point.
If dehumidification is terminated by a condition other
than the humidity sensor, e.g., an out-of-range or
compressor shutdown condition, the heat relay is
de-energized immediately.