T-354
5–10
5. When the calculation reaches -250, contacts TC and TN are opened to de-energize compressor and con
denser fan motors. The cool light is also de-energized.
6. The evaporator fan motors continue to run to circulate air throughout the container. The in-range light
remains illuminated as long as the supply air is within tolerance of set point.
7. When the supply air temperature increases to 0.2
C (0.4
F) above set point and the three minute off time
has elapsed, relays TC and TN are energizes to re start the compressor and condenser fan motors. The
cool light is also illuminated.
5.10.2
Sequence of Operation - Perishable Mode Heating
NOTE
The unit will heat only when in the Perishable Mode, relay TH is electronically locked out when in the
Frozen Mode.
1. If the air temperature decreases 0.5
C (0.9
F) below set point, the system enters the heating mode (see
). The controller closes contacts TH (see
) to allow power flow through the heat termi-
nation thermostat (HTT) to energize the heaters (HR). The HEAT light is also illuminated. The evaporator
fans continue to run to circulate air throughout the container.
2. When the temperature rises to 0.2
C (0.4
F) below set point, contact TH opens to de-energize the heaters.
The HEAT light is also de-energized. The evaporator fans continue to run to circulate air throughout the con-
tainer.
3. A safety heater termination thermostat (HTT), attached to an evaporator coil support, will open the heating
circuit if overheating occurs.
Figure 5.6 Perishable Mode Heating
CONTROL TRANSFORMER
POWER TO
CONTROLLER
SIGNAL TO
CONTROLLER
SIGNAL TO
CONTROLLER
ENERGIZED
DE-ENERGIZED
FOR FULL DIAGRAM AND
LEGEND, SEE SECTION 7
Summary of Contents for 69NT40-541-306
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