Carrier 69NT40-541-306, Операция и обслуживание

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4–5 T-354
To access the function codes, perform the following:
a. Press the CODE SELECT key, then press an arrow key until the left window displays the desired code
number.
b. The right window will display the value of this item for five seconds before returning to the normal display
mode.
c. If a longer time is desired, press the ENTER key to extend the time to 30 seconds.
4.3 MODES OF OPERATION
The operational software responds to various inputs. These inputs come from the temperature and pressure sensors,
the temperature set point, the settings of the configuration variables, and the function code assignments. The action
taken by the operational software will change if any one of the inputs changes. Overall interaction of the inputs is
described as a “mode” of operation. The modes of operation include perishable (chill) mode and frozen mode.
Descriptions of the controller interaction and modes of operation are provided in the following sub paragraphs.
4.3.1 Temperature Control - Perishable Mode
With configuration variable CnF26 (Heat Lockout Temperature) set to -10

C, the perishable mode of operation is
active with set points above -10

C (+14

F ). With the variable set to -5

C, the perishable mode is active above -5

C
(+23

F ). Refer to Table 4–4 .
When in the perishable mode, the controller maintains the supply air temperature at set point, the SUPPLY indica-
tor light will be illuminated on the display module, and the default reading on the display window will be the supply
temperature sensor reading.
When the supply air temperature enters the in-range temperature tolerance (as selected at function code Cd30),
the in-range light will energize.
4.3.2 Evaporator Fan Operation
Opening of an evaporator fan internal protector will shut down a unit with Normal Evaporator Fan Operation.
(CnF32 set to 2EFO). On units equipped with Single Evaporator Fan Capability (CnF32 set to 1EFO), additional
relays are installed to allow the unit to continue to operate on a single fan (refer to
Table 4–4 ).
4.3.3 Defrost Interval
Controller function code Cd27 sets two modes for defrost initiation - either user-selected timed intervals or auto-
matic control. The user-selected values are 3, 6, 9, 12, or 24 hours and the factory default for the timed interval is
12 hours (some units may be configured to allow defrost to be disabled altogether; in this case a user-selected
value of OFF will be available). Refer to
Table 4–5 .
In perishable mode, perishable-pulldown mode, or frozen-pulldown mode, automatic defrost starts with an initial
defrost set to three hours and then adjusts the interval to the next defrost based on the accumulation of ice on the
evaporator coil. In this way, defrosts are scheduled to occur only when necessary.
Once setpoint has been reached in frozen operation, the automatic selection will set the time interval to 12 hours
for the first two defrosts once the return probe is reading below the frozen setpoint and then adjust to 24 hours
thereafter.
All defrost interval times reflect the number of compressor runtime hours since the last defrost de-ice cycle. The
minimum defrost interval under the automatic setting is three hours, while the maximum is 24. In frozen mode, the
amount of wall-clock time necessary to accumulate a given amount of defrost interval time will exceed the defrost
interval time by a factor of two to three depending on the compressor duty-cycle. Defrost interval time is not accu-
mulated in any mode until the defrost termination sensor reads less than 10

C (50

F).
4.3.4 Failure Action
Function code Cd29 may be operator set to allow continued operation in the event the control sensors are reading
out of range. The factory default is full system shutdown (refer to
Table 4–5 , page).
4.3.5 Generator Protection
Function codes Cd31 and Cd32 may be operator set to control start-up sequence of multiple units and operating
current draw. The factory default allows on demand starting of units and full current draw (refer to
Table 4–5 ).