CRR-20 & CRR-40, September 1999
µ
P-D Controller
Sequence of Operation
4-11
Economy Mode Operation
The Economy Mode reduces unit power consumption by
reducing evaporator fan operation on both fresh and frozen
loads. The use of the Economy Mode should be established by
the shipper and the type of cargo. The Economy Mode option
is turned on from Setpoint menu of the controller.
NOTE: If the Economy Mode is set to ON, the con-
troller display will show “ECON ON” for 1 second
every 10 seconds.
• Fresh Loads (return air temperatures of -9.9 C (14.1 F) and
above): Evaporator fans operate on low speed whenever the
container temperature is In-range.
• Frozen Loads (return air temperatures of -10 C (14 F) and
below): The evaporator fans stop during the Null mode. A
null state timer automatically re-starts the evaporator fans on
low speed for 5 minutes every 45 minutes.
The Economy Mode also modifies the temperature control
algorithm on frozen loads to extend the Null mode. The unit
continues on Cool operation until return air temperature
reaches ECMIN temperature. Default ECMIN setting is 2.0 C
(3.6 F) below setpoint. ECMIN temperature is adjustable
from 0 to 5 C (0 to 8.9 F) below setpoint through the
Configuration menu of the controller.
The unit remains in Null until the return air temperature
increases to ECMAX temperature at the expiration of a 45
minute Null state time sequence. Default ECMAX setting is
.2 C (0.4 F) above setpoint. ECMAX setting is adjustable
from 0 to 5 C (0 to 8.9 F) above setpoint through the
Configuration menu of the controller.
NOTE: On Frozen loads, supply and return air tem-
peratures may vary considerably during Economy
mode operation due to long periods of no air circula-
tion. On Chill loads, container air temperatures may
vary 1 C to 3 C (1.8 F to 5.4 F) above setpoint in high
ambient temperatures.
Sequence Of Operation
Unit Start-up
A sequence start of the required loads occurs during initial
start-up of the controller. If cooling (or heating) is required,
the unit operates in the cool (or heat) mode until the control-
ling sensor reaches setpoint.
• When the unit On/Off switch is turned ON, the Status
Indicator LEDs and display turn On and then Off.
• “Phase Check” appears in the controller display while
the controller determines the correct phase sequence.
Phase selection takes 50 to 80 seconds; or more on
extremely noisy power lines. The controller then ener-
gizes phase select contactor ABC or CBA.
• The setpoint and controlling air sensor temperature are
displayed.
• The evaporator fan motors start. Evaporator fans operate
on high speed at return air temperatures of -9.9 C (14.1
F) and above (except when Economy mode is ON and
temperature is In-range). Evaporator fans operate on
low speed at return air temperatures of -10 C (14 F) and
below (except during Null with Economy mode ON).
• The condenser fan motor also starts if the condenser fan
pressure switch is open (pressure above 1380 +/- 50 kPa,
13.80 +/- 0.5 bar, 200 +/- 7 psig) and the controller calls
for cooling.
• If the controller calls for cooling, the compressor motor
starts and the liquid line solenoid valve opens (ener-
gizes). If the unit starts in Modulation Cool, compressor
start-up can be delayed up to 3 minutes while the evapo-
rator pressure regulator (KVQ) valve opens or closes to
the required setting. Unit operates in cool and modula-
tion cool until the controlling sensor reaches setpoint.
• If the controller calls for heating, the electric heaters are
energized. Unit operates in heat until the controlling
sensor reaches setpoint.
• Power limit is active when the unit is operating in the
Cool mode. This means the KVQ valve may be ener-
gized to reduce the cooling load on the compressor,
thereby reducing total unit power consumption.
• Controller turns ON the In-range LED when the control-
ling sensor temperature is within 1.7 C (3.0 F) of setpoint.
Summary of Contents for CRR-20
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