Carrier 69NT40-561-201, Operation & Service Manual, Page: 33 / 117

3 − 4 T-364
3.2.2 Operational Software (Cd Function Codes)
The operational software is the actual operation
programming of the controller which activates or
deactivates components in accordance with current unit
operating conditions and selected modes of operation.
The programming is divided into function codes. Some
of the codes are read only, while the remaining codes
may be user configured. The value of the user
configurable codes can be assigned in accordance with
user desired mode of operation. A list of the function
codes is provided in Table 3 − 5.
To access the function codes:
a. Press CODE SELECT, then press an arrow key until
the left window displays the desired function code.
b. The right window will display the selected function
code value for five seconds before returning to nor-
mal display mode.
c. If additional time is required, pressing the ENTER key
will extend the display time to 30 seconds.
3.3 MODES OF OPERATION
General operation sequences for cooling, heating and
defrost are provided in the following sub-paragraphs.
Schematic representation of controller operation is
provided in Figure 3 − 5 & Figure 3 − 8.
Operational software responds to various inputs. These
inputs come from the temperature sensors, pressure
transducers, the temperature set point, the settings of
the configuration variables and the function code
assignments. The actions taken by the operational
software changes as the input values change. 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.
3.3.1 Start up - Compressor Phase Sequence
At start up, the controller logic checks for proper phase
sequencing and compressor rotation. If incorrect se-
quencing is causing the compressor and three-phase
evaporator fan motors to rotate in the wrong direction,
the controller will energize or de-energize relay TCP as
required (see Figure 7-2). Relay TCP will switch its con-
tacts, energizing or de-energizing relays PA and PB.
Relay PA is wired to energize the circuits on L1, L2 and
L3. Relay PB is wired to energize the circuits on L3, L2,
and L1, thus providing reverse rotation.
3.3.2 Start up - Compressor Bump Start
At start up, the controller logic will initiate a compressor
bump start procedure to clear liquid refrigerant from the
compressor. If suction and discharge pressures have
equalized, the compressor will perform three com-
pressor bump starts. A compressor bump start may also
occur after a defrost cycle has been completed.
During Bump Start, the EEV will close. Relays TS, TQ,
TN, TE, and TV will be de-energized (opened). The res-
ult of this action will close the ESV and shut all fans off.
The compressor will start for 1 second, then pause for
five seconds. This sequence will be repeated two more
times. After the final bump start the unit will pre-position
the EEV to the correct starting position, pause and start
up.
3.3.3 Perishable Mode Temperature Control
In Perishable Mode, the controller maintains the supply
air temperature at set point, the SUPPLY indicator light
is illuminated and the default reading on the display win-
dow is the supply temperature sensor reading.
When the supply air temperature enters the in-range
temperature tolerance (Cd30), the green IN-RANGE
light will energize.
With set points above - 10 C (14 F), perishable mode is
active.
3.3.4 Perishable Pulldown
When the system is in Perishable Pulldown Mode, the
highest priority is given to bringing the container down to
set point. When cooling from a temperature that is more
than 2.5 C (4.5 F) above set point, the system will be in
perishable pulldown mode in economized operation.
However, pressure and current limit functions may re-
strict the valve if either exceeds the preset value.
3.3.5 Perishable Steady State
Perishable Steady State is used to maintain the control
temperature near a setpoint that is above the heat lock-
out temperature.
Once set point is reached, the unit will transition to per-
ishable steady state mode. This results in unloaded op-
eration by cycling the DUV to limit capacity and maintain
steady temperature control.
The unit is capable of maintaining supply air tempera-
ture to /-0.2 C (+/-0.36 F) of set point. Supply
air temperature is controlled by positioning of the elec-
tronic expansion valve (EEV), cycling of the digital un-
loader valve (DUV), cycling of the compressor, and cycl-
ing of the heaters.
3.3.6 Perishable Idle, Air Circulation
Perishable Idle Mode is used when it is unnecessary to
run the compressor to maintain control temperature. If
the controller has determined that cooling is not required
or the controller logic determines suction pressure is at
the low pressure limit, the unit will transition to Perish-
able Idle Mode. During Perishable Idle Mode, the com-
pressor is turned off, but the evaporator fans continue to
run to circulate air throughout the container. If tempera-
ture rises +0.2 C (+0.4 F) above set point, the unit will
transition back to perishable steady state.
3.3.7 Perishable Heating
When it is necessary to raise the control temperature,
the system will enter Perishable Heating Mode. If the
temperature drops to 0.5 C (0.9 F) below set point, the
unit will transition to Perishable Heating Mode, and the
heaters will be energized. The unit will transition back to
Perishable Idle Mode when the temperature rises to
0.2 C (0.4 F) below the set point, and the heaters will
de-energize.