Perishable Mode Heating - Sequence Of Operation; Perishable Mode - Trim Heat; Frozen Mode - Temperature Control; Frozen Steady State - Carrier PrimeLINE Operation And Service Manual

4.3.12

Perishable Mode Heating - Sequence of Operation

a. If the supply air temperature decreases 0.5°C (0.9°F) below setpoint, the system enters the heating mode
(see Figure 4.3). The controller closes contacts TH (see
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 (0.4°F) below setpoint, 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.
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
maximum 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 setpoint, 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.
When CnF26 (Heat Lockout Temperature) is set to -10°C, frozen mode is active with setpoints below -10°C
(+14°F). When CnF26 is set to -5°C, frozen mode is active with setpoints below -5°C (+23°F).
When the system is in Frozen mode, the highest priority is given to bringing the container down to setpoint, the
system will remain in economized operation.
4.3.15

Frozen Steady State

Frozen cargos are not sensitive to minor temperature changes, and the frozen temperature control system takes
advantage of this to greatly improve the energy efficiency of the unit. Frozen range temperature control is
accomplished by cycling the compressor on and off as the load demand requires.
Once the frozen setpoint is reached, the unit will transition to frozen steady state (economized operation).

Figure 4.5 Perishable Mode Heating

ENERGIZED
DE-ENERGIZED
F
HPS
IP-CM TN
IP-EM1 IP-EM2
HTT
ESV
TS
NOTE
4–23
Figure 4.5) to allow power flow through the heat
ST
24 VOLT POWER
TC CH
CF
TV EF ES
TE EF
TH
HR
T-362