4–13 62-12259
4.8.1.2 Defrost Based on Time
Time interval between defrosts is selected in the Functional Parameters. The parameter value may be set
to 1.5, 3, 6, or 12 hours. The factory default setting is six hours.
NOTE
The defrost timer will not count when the unit is in defrost, the unit is in a Start/Stop off cycle or the
DTT is greater than 40.0°F (4.4°C).
4.8.2 Defrost Modes
There are two Defrost modes available:
4.8.2.1 Normal Defrost Mode
Normal Defrost mode is entered if RAT is less than 32.0°F (0.0°C) and SAT is less than 45.0°F (7.2°C).
Defrost will be accomplished by shutting down the refrigeration system while the heaters (HTCON1 and
HTCON2) are energized.
Electric heaters will be used for all defrost with fans off when temperatures are less than 32°F (0.0°C) for
RAT and less than 45°F (7.2°C) for SAT. for defrost requests at temperatures higher (RAT > 35°F, SAT >
45°F, heaters will not be energized.
4.8.3 Defrost Termination
When in defrost mode, defrost will terminate when the DTT rises to 55°F (12.8°C).
During Defrost Termination, the heaters will de-energize, and the engine will go to low speed.
The EVXV will open, and the evaporator coil will begin to cool down. The evaporator fans will not come on right
away, so that warm air is not blown into the refrigerated compartment, but will wait for the evaporator to cool down,
up to a maximum of eight minutes.
If there is a DTT sensor alarm present, defrost will terminate after 10 minutes.
NOTE
Defrost mode uses a Defrost Duration Timer that allows for a maximum of 45 minutes in defrost. If
defrost is not terminated during the 45 minutes, the control system will end the defrost cycle, and show
the alarm “DEFROST NOT COMPLETE”. When this occurs, the Defrost Interval Timer is set for 1.5
hours, at which time the unit will go into defrost again.
4.9 User Selected Override Operation
Three optional software override programs are available to the user. These programs include: Fresh Protect, Tem-
perature Range Lock and Product Shield. Information on how the unit operates under these programs is provided
in the following sub-paragraphs.
4.9.1 Fresh Protect
• Fresh Protect is available when the unit is operating in Cool.
• Fresh Protect is available when the setpoint is at or between 32 to 65°F (0 to 18.4°C).
• Fresh Protect is NOT a positive temperature control, drift above and below the Supply Air Limit will be
seen as the system balances out.
• Fresh Protect control will be accomplished by varying the position of the CSMV.
• Fresh Protect values can be set to allow for a different limit for Start-Stop than used in Continuous Run.
• Fresh Protect can be set to OFF or within the range of -21.6°F to -3.6°F (-12°C to -2°C).
NOTE
These values are all negative (except for 0), therefore, when the value is added to the setpoint, the
result will be a temperature that is less than the setpoint.
4.9.2 Temperature Range Lock 1 and 2
Range Lock is a group of Configurations which may be set to lock the unit into Start-Stop or Continuous Operation
for various setpoint ranges.
To Next Page
Loading...
