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6
MultiFlex CUB-II and
CUB-TD Software Over-
view
The CUB-II is capable of controlling all vital
systems of a single condensing unit, including
compressors, condenser fans, evaporators and
case circuit systems. Extended logging and
alarm control capabilities require connection to
an E2 or Einstein RX refrigeration controller.
6.1. Compressor Control
Since a single condensing unit has a single
compressor, the MultiFlex CUB-II's pressure
control strategy uses simple Cut In/Cut Out
strategy for activating and deactivating the com-
pressor. The compressor may be controlled
either by suction pressure or case temperature.
6.1.1. Suction Pressure Compressor
Control
Using the Suction Pressure Control strategy,
the CUB-II compares the suction pressure to a
set of Cut In/Cut Out setpoints. If the suction
pressure rises higher than the Cut In setpoint, the
compressor is activated and remains activated
until the suction pressure falls below the Cut Out
setpoint.
To prevent short-cycling of the compressor,
minimum ON and OFF times may be used in
this strategy.
6.1.2. Case Temperature Compres-
sor Control
Using the Case Temperature Control strat-
egy, the CUB-II only activates the compressor
when refrigeration is necessary in the case. This
strategy uses a temperature setpoint and a dead-
band. When the case temperature is above the
Compressor Control
setpoint plus one-half the deadband, the com-
pressor will turn ON and will remain ON until
the case temperature falls below the setpoint
minus one-half the deadband.
NOTE: A suction transducer is required even
for temperature control and is used to prevent
the compressor from operating below the min-
imum suction pressure setpoint.
6.1.2.1.
Pump Down
If the CUB-II is using the Temperature strat-
egy, it also has the option of using a special
Pump Down mode to pump refrigerant out of the
evaporator coil when going from Refrigeration
to Idle or from Refrigeration to Defrost.
A Pump Down causes the refrigeration sole-
noid to shut while keeping the compressor ON.
The compressor will remain ON until the suction
pressure drops below a minimum setpoint (or
until a fail-safe time elapses).
Idle Pump Down With Door Switches
If a door switch is available and Idle Pump
Down mode is enabled, the CUB-II will do a
Pump Down every time a door switch is acti-
vated.
6.1.2.2.
Fallback Pressure Setpoints
When in Temperature strategy, if the case
temperature sensors fail or the CUB-II is other-
wise unable to determine the case circuit air tem-
perature, the CUB-II will cease operating in
Case Temperature Compressor Control mode
and use fallback suction pressure Cut In/Cut Out
setpoints to control the compressor. This fall-
back mode operates exactly like the Suction
Pressure Compressor Control mode described in
Section 6.1.1.
The CUB-II will continue to operate using
the fallback pressure setpoints until a case tem-
perature sensor value becomes available. The
CUB-II will then resume Temperature strategy
control.
MultiFlex CUB-II and CUB-TD Software Overview • 15
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