CSR-20 & CSR-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 cycles between ON and OFF
based on a control algorithm. Typically, the condenser
fan will typically be ON when:
- the compressor temperature is above 50 C (122 F)
and increasing, or
- the condenser temperature is above 35 C (95F).
• If the controller calls for cooling, the compressor motor
starts. On Chill Loads, the unit operates in cool until the
supply air temperature reaches setpoint. On Frozen
Loads, the unit operates in cool until the return air tem-
perature reaches 1.0 C (1.8 F) below setpoint.
• The modulation valve remains open during initial start-
up on cooling.
• Power limit is active when the unit is operating in a cool-
ing mode. This means the modulation valve may be
energized to reduce the cooling load on the compressor,
thereby reducing total unit power consumption.
• Chill Loads Only: If the controller calls for heating, the
electric heaters are energized. Unit operates in heat until
the supply air temperature reaches setpoint.
• Controller turns ON the In-range LED when the control-
ling sensor temperature is within 1.7 C (3.0 F) of setpoint.
