CPC MultiFlex PAK, Руководство пользователя

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Condenser Control PAK Software Overview • 21
When the number of cases classified as poor
performers exceeds the user-defined maximum
number of cases to be excluded, it will compare
each case’s deviation from the float temperature
setpoint to determine which cases are the worst
performers (highest deviations are excluded
first). If desired, an alarm or notice may be gen-
erated when a poor-performing case is excluded.
6.1.5.4. Suction Float During Loss of
Communication
Because suction float requires a large num-
ber of inputs and the MultiFlex PAK board has
only sixteen, the PAK cannot use suction float in
stand-alone mode. When the PAK is in stand-
alone mode, either by design or because of loss
of communication with its parent E2, suction
float will be disabled and the pack will be con-
trolled using the fixed suction pressure setpoint.
6.2. Condenser Control
The MultiFlex PAK uses a temperature dif-
ferential (TD) strategy similar to the current
Condenser TD strategy implemented in E2’s
own Condenser Control cell.
TD control in the MultiFlex PAK uses a con-
trol value that is calculated by subtracting the
ambient air temperature near the condenser fans
from the calculated discharge temperature (cal-
culated by converting the discharge pressure to
temperature based on the refrigerant type).
This control value is compared to a fixed
temperature differential set point, and condenser
fans and/or sprays are activated or deactivated to
attempt to keep the control value at or near the
TD set point.
6.2.1. Condenser Control Strate-
gies
6.2.1.1. Staged Fans
In the Staged Fans strategy, when the TD
value is above the setpoint, the PAK activates
the FanStage outputs in sequence, beginning
first with FanStage1 and ending with FanStage4.
When the TD falls below the setpoint, the PAK
deactivates the FanStage outputs in reverse
sequence, beginning with FanStage4 and ending
with FanStage1.
The PAK observes fan ON and OFF inter-
stage delays as it activates and deactivates fan
stages.
6.2.1.2. VSD Fan
The VSD Fan strategy is designed to control
TD using a variable-speed fan.
The PAK uses two outputs to control the VS
fan inverter: a relay or digital output called
VSEnable that is CLOSED to send a "forward-
run" command to the inverter, and an analog out-
put called VSDAnalog whose voltage com-
mands the inverter to run at a specific percentage
of its maximum speed.
When the TD is above the setpoint, the PAK
will close the VSEnable output and set the
VSDAnalog output voltage to the user-defined
minimum fan speed percentage. The VS fan will
increase RPM from the minimum fan speed up
to the maximum fan speed as long as the TD is
above setpoint. When the TD falls below the set-
point, the fan speed is reduced until the mini-
mum fan speed is reached, at which point the fan
will be deactivated after a user-defined delay
time.
6.2.1.3. Fan Sequencer
Because the MultiFlex PAK board has only
twelve outputs, to conserve the number of out-
puts required, the PAK supports control of con-
denser fan stages through the use of a single