Carrier 69NT40-541-500 Operation And Service Manual page 60

CODE TITLE
Configurable Functions - Cd27 through Cd37 are user-selectable functions. The operator can change the value
of these functions to meet the operational needs of the container.
Defrost Interval
Cd27 (Hours or
Automatic)
Temperature Units
Cd28 (Degrees C or
Degrees F)
Cd29 Failure Action Mode
T-363
Table 4–5 Controller Function Codes (Continued)
Configurable Functions
There are two modes for defrost initiation, either user-selected timed intervals or
automatic control. The user-selected values are (OFF), 3, 6, 9, 12, 24 hours, AU-
TO, or PuLS. Factory default is "AUTO".
Automatic defrost starts with an initial defrost at three hours and then adjusts the
interval to the next defrost based on the accumulation of ice on the evaporator
coil. Following a startup or after termination of a defrost, the time will not begin
counting down until the defrost temperature sensor (DTS) reading falls below set
point. If the reading of DTS rises above set point any time during the timer count
down, the interval is reset and the countdown begins over.
If the DTS fails, alarm code AL60 is activated and control switches over to the re-
turn temperature sensor. The controller will act in the same manner as with the
DTS except the return temperature sensor reading will be used.
If CnF23 is configured to SAv (save), then the value of the defrost interval timer
will be saved at power down and restored at power up. This option prevents short
power interruptions from resetting an almost expired defrost interval, and possibly
delaying a needed defrost cycle.
The defrost interval timer counts only during compressor run time.
Configuration variable (CnF11) determines whether the operator will be allowed
to chose OFF as a defrost interval option.
Configuration variable (CnF64) determines whether the operator will be allowed
to choose PuLS as a defrost interval option. For units operating with PuLS select-
ed, defrost interval is determined by the unit temperature setpoint and the Evap-
orator Fan Pulsing Temperature Setting (Cd60). When the unit temperature
setpoint is equal to or less than the Evaporator Fan Pulsing Temperature Setting,
the defrost interval is set to 6 hours. Otherwise, the defrost interval is determined
using the Automatic Defrost Interval Determination logic. In either case, PuLS re-
mains displayed in this function select code.
After a new Defrost Interval is selected, the previously selected Interval is used
until the next defrost termination, the next time the DTT contacts are OPEN, or the
next time power to the control is interrupted. If the previous value or the new value
is OFF, the newly selected value will be used immediately.
If any Auto Pretrip sequence is initiated, Cd27 will be set to 'AUTO' unless CnF49
(OEM Reset) is set to Custom AND CnF64 (Evaporator Fan Pulsing Logic) con
figuration variable is set to IN, in which case Cd27 will be set to PuLS.
This code determines the temperature units (C or F) which will be used for all
temperature displays. The user selects C or F by selecting function code Cd28
and pushing the ENTER key. The factory default value is Celsius units. This func-
tion code will display ----- if CnF34 is set to F.
This is the desired action to be taken if an alarm occurs that severely limits the
capability of the control system. Depending upon what alarm has occurred, the ac-
tual action taken may not be the same as the desired failure action.
The user selects one of four possible actions as follows:
A - Full Cooling (stepper motor SMV at maximum allowed opening)
B - Partial Cooling (stepper motor SMV 11% open)
C - Evaporator Fan Only
D - Full System Shutdown - Factory Default
4–28
DESCRIPTION
NOTE