Perishable Mode Cooling - Sequence Of Operation; Perishable Mode Heating - Sequence Of Operation; Sequence Of Operation - Perishable Mode (Capacity Trim Heat); Figure 4.6 Perishable Mode - Cooling - Carrier 69NT40-561-019 Operation And Service Manual

4.3.7

Perishable Mode Cooling - Sequence of Operation

In the Standard Perishable Mode of Operation, the evaporator motors run in high speed. In the Econ-
omy Perishable Mode, the fan speed is varied.
With supply air temperature above set point and decreasing, the unit will cool with the condenser fan motor (CF),
compressor motor (CH), evaporator fan motors (EF) energized and the COOL light illuminated. (See
Also, if current or pressure limiting is not active, the controller may close contacts TS to open the economizer sole-
noid valve (ESV) and place the unit in economized operation.
When the air temperature decreases to a predetermined tolerance above set point, the in-range light is illuminated.

Figure 4.6 Perishable Mode - Cooling

ENERGIZED
DE- - ENERGIZED
F
HPS
IP- - CM
IP- - EM1 IP- - EM2
HTT
ESV
TS
NOTE
The EEV and DUV are independently operated by
the microprocessor. For full diagrams and legend,
see Section 8.
4.3.8

Perishable Mode Heating - Sequence of Operation

a. If the 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
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.
b. When the temperature rises to 0.2°C (0.4°F) below set point, contacts TH open to de-energize the heaters. The
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.
4.3.9

Sequence of Operation - Perishable Mode (Capacity 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. Trim heat is enabled only if (12.77°C < set point < 15.55°C [54.99°F < set point
< 59.99°F]) and (-6.67°C < ambient temperature < 1.66°C [19.99°F < ambient temperature < 34.99°F]).
ST
24 VOLT POWER
TC CH
CF
TN
TV EF
ES
TE EF
TH HR
NOTE

Figure 4.7 Perishable Mode Heating

ENERGIZED
DE- - ENERGIZED
F
HPS
IP- - CM
IP- - EM1
HTT
TS
The EEV and DUV are independently operated
by the microprocessor. For full diagrams and
legend, see Section 8
Figure 4.7) to allow power flow through the heat termi-
4–7
Figure
ST
24 VOLT POWER
TC
CF
TN
TV EF ES
TE EF
IP- - EM2
TH
HR
ESV
NOTE
4.6).
CH
T-359