Carrier 69NT40-561-300, Operation And Service Manual

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4–9 T-365
f. If the supply air temperature increases to 0.2°C (0.36°F) above set point, contacts TC and TN close to
restart the compressor and condenser fan motors in standard steady state operation. The white COOL light
is also illuminated.
g. If the supply air increases more than 2.5°C (4.5°F) above set point temperature, contacts TS will close to
energize and open the ESV, placing the unit in pull down mode.
4.3.12 Perishable Mode Heating - Sequence of Operation
a. If the supply air temperature decreases 0.5°C (0.9°F) below set point, the system enters the heating mode.
(See Figure 4.5 ). The controller closes contacts TH (see Figure 4.7 ) to allow power flow through the heat
termination thermostat (HTT) to energize the heaters (HR). The orange HEAT light is also illuminated. The
evaporator fans continue to run to circulate air throughout the container.
b. When the supply air temperature rises to 0.2°C (0.36°F) below set point, contact TH opens to de-energize
the heaters. The orange HEAT light is also de-energized. The evaporator fans continue to run to circulate air
throughout the container.
c. The safety heater termination thermostat (HTT) is attached to an evaporator coil circuit and will open the
heating circuit if overheating occurs.
Figure 4.7 Perishable Mode Heating
NOTICE
The EEV and DUV are independently operated by the microprocessor. For full diagrams and
legend, see
Section 8 .
4.3.13 Perishable Mode - Trim Heat
If the system capacity has been decreased to the lowest allowable capacity and conditions exist that warrant max-
imum temperature stability the controller will pulse the HR relay to energize the evaporator heaters in sequence
with the compressor digital signal.
4.3.14 Frozen Mode - Temperature Control
In Frozen Mode, the controller maintains the return air temperature at set point, the yellow RETURN indicator light
is illuminated, and the default reading on the display window is the return temperature sensor (RTS) reading.
When the return air temperature enters the in-range temperature tolerance (Cd30), the green IN-RANGE light will
energize.
24 VOLT POWER
ENERGIZED
DE-ENERGIZED
TG
ST
F
HPS
CH
IP-CM
TC
CF
TE
IP-EM1
EF
IP-EM2
HTT
TH
HR
ESV
TS
TV
EF ES
TN
FS
LC
TG CF FS
LC