Carrier 69NT40-541-300, Операция и обслуживание

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T-318 3 − 6
Two timers are activated during dehumidification to
prevent rapid cycling and consequent contactor wear:
1. Heater debounce timer (three minutes)
− The heater
debounce timer is started whenever the heater
contactor status is changed. The heat contactor re-
mains energized (or de-energized) for at least three
minutes even if the set point criteria is satisfied.
2. Out-of-range timer (five minutes) − The out-of-range
timer is started to maintain heater operation during a
temporary out-of-range condition. If the supply air
temperature remains outside of the user selected in-
range setting for more than five minutes, the heaters
will be de-energized to allow the system to recover.
The out-of-range timer starts as soon as the temper-
ature exceeds the in-range tolerance value set by
Cd30.
3.3.7 Perishable, Dehumidification − Bulb Mode
Bulb mode is an extension of dehumidification, which
allows changes to the evaporator fan speed and/or
defrost termination set points.
Bulb mode is active when Cd35 is set to “Bulb.” Once
bulb mode is activated, the user may then change the
dehumidification mode evaporator fan operation from
the default (speed alternates from low to high each hour)
to constant low or constant high speed. This is done by
toggling Cd36 from its default of “alt” to “Lo” or “Hi” as
desired. If low speed evaporator fan operation is
selected, the user has the additional capability of
selecting dehumidification set points from 60 to 95%
(instead of the normal 65 to 95%).
In addition, if bulb mode is active, Cd37 may be set to
override the previous defrost termination thermostat
settings (refer to paragraph 3.3.17). The temperature at
which the defrost termination thermostat will be
considered “open” may be changed [in 0.1 ° C (0.2 ° F)
increments] to any value between 25.6 ° C (78 ° F) and
4 ° C (39.2 F). The temperature at which the defrost
termination thermostat is considered closed for interval
timer start or demand defrost is 10 ° C (50 ° F) for “open”
values from 25.6
°
C down to a 10
°
C setting. For “open”
values lower than 10
°
C, the “closed” values will
decrease to the same value as the “open” setting. Bulb
mode is terminated when:
1. Bulb mode code Cd35 is set to “Nor.”
2. Dehumidification code Cd33 is set to “Off.”
3. The user changes the set point to one that is in the
frozen range.
When bulb mode is disabled by any of the above, the
evaporator fan operation for dehumidification reverts to
“alt” and the DTS termination setting resets to the value
determined by CnF41.
3.3.8 Perishable Economy
Economy fan mode is an extension of Perishable Mode,
and is only applicable to units with two speed evaporator
fan motors. Economy Mode is activated Cd34 is set to
“ON.“ Economy Mode is provided for power saving
purposes, and is generally used during the
transportation of temperature tolerant cargo or
non-respiration items that do not require high airflow for
removing respiration heat. There is no active display
that indicates Economy Mode has been activated. To
check for economy fan mode, perform a manual display
of Cd34.
In order to achieve economy mode, a perishable set
point must be selected prior to activation. When
economy mode is active, the evaporator fans will be
controlled as follows:
At the start of each cooling or heating cycle, the
evaporator fans will run in high speed for three
minutes.
After the initial three minutes, they will then be
switched to low speed any time supply air temperature
is /-0.25 C (0.45 F) of set point and return air
temperature is less than or equal to supply air
tempe3 C (5.4 F).
The fans will continue to run in low speed for one hour.
At the end of the hour, the evaporator fans will switch
back to high speed and the cycle will be repeated.
3.3.9 Perishable Mode Cooling − Sequence of
Operation
NOTE
In Standard Perishable Mode, the evaporator
motors run in high speed. In Economy Fan
Mode, fan speed is varied.
NOTE
In low temperature ambients, the condenser
fan will be cycled by the controller to maintain
proper condensing pressure.
a. With supply air temperature above set point and de-
creasing, the unit will cooling with the condenser fan
motor (CF), compressor motor (CH), evaporator fan
motors (EF) energized, and the white COOL light illu-
minated (see Figure 3-6).
CONTROL TRANSFORMER
POWER TO
CONTROLLER
SIGNAL TO
CONTROLLER
SIGNAL TO
CONTROLLER
ENERGIZED
DE − ENERGIZED
FOR FULL DIAGRAM AND
LEGEND, SEE SECTION 7
NOTE: HIGH SPEED EVAPORATOR FAN SHOWN. FOR LOW SPEED
CONTACT TE IS DE-ENERGIZED AND CONTACT TV IS ENERGIZED
Figure 3-6 Perishable Mode Cooling