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FIXED
SPEED CONDENSER FAN BANK CONTROL
The
CF-1000 Condenser Fan Control System is
an all electronic
control system that can efficiently
operate a fixed fan speed condenser fan
bank, maintaining a fixed or floating
discharge pressure.
Easy to Use--The
CF-1000 is operated entirely by the front
control panel. The system is menu-driven,
and the four key keypad allows the user
to make changes quickly by answering the
prompted questions. Data is shown on a 1
by 10 FIP display.
Adjusts to Operating
Conditions--The CF-1000 uses
"Heuristics" to continuously
analyze refrigeration performance and
modify the operation of the fan to
maintain a stable head pressure.
Operating Parameters--All
pressure operating parameters, such as
Suction Pressure Setpoint, are single
value settings. No Cut In Cut Out values
or staging levels are required. Once the
operating level is entered, the CF-1000
will stage the fans in their most
efficient mode to maintain the operating
pressures.
Memory Protection--The
CF-1000 uses the latest EEPROM and static
RAM technology to store configuration
data, operational settings, and the alarm
log. A power outage will not alter or
erase any stored data. The system clock
is battery backed and will retain the
time and date for up to 5 years without
power. The clock is Y2K compliant and
leap year compliant until year 2100.
GenCom Communications
Capability--With a MS-DOS or
Windows operating system based computer
and a modem, a user can monitor and
control several CF-1000 units from within
a store or from a remote location. This
option provides full accessibility to the
CF-1000's functions and keeps the user
aware of system alarm and operating
conditions.
CONDENSER CONTROL
The CF-1000 can operate a remote
condenser with up to seven independent
fan banks and one split condenser valve.
The CF-1000 can monitor the head
pressure, ambient temperature, liquid
drop leg temperature, a gas defrost
status signal, and a heat reclaim status
signal.
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Sequential Staging--The
CF-1000 will sequentially stage
the fan banks in the FILO format
(first on last off). The fan bank
closest to the condenser input
manifold should always be
assigned as the first, or
primary, fan bank. The CF-1000 will
keep the first fan bank running
nearly constantly to prevent
expansion and contraction at the
pipe and tube sheet joints.
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Parallel Fan Bank
Control--If the condenser has a primary
side and a secondary, or split, side with fans on
each side, both sets of fans should be controlled by
the same condenser relay. The contactor power for
the split fans should also be controlled by the
Split Condenser Relay ( Relay #6)
Fixed Head Pressure
Control--The CF-1000
can stage the condenser fan banks
based upon a fixed head pressure
setpoint.
Floating Head
Pressure Control--The
CF-1000 can stage the condenser fan
banks based upon the temperature of
the liquid drop leg temperature and
ambient temperature. The CF-1000 will
maintain the liquid at the Ambient
Sub Cooled Refrigerant setpoint.
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Split Condenser--The
CF-1000 will attempt to maintain
the condenser in its smallest
configuration. If the CF-1000 can
maintain the head pressure while
in the "split
condenser" mode even though
the ambient temperature is above
70 °F, the CF-1000 will do so. The
CF-1000 will lock into the Split
mode when the ambient temperature
is below a settable ambient
temperature setpoint. The CF-1000
will only come out of split
condenser when the following
occurs:
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The head pressure reaches 85%
of the high head pressure
alarm level.
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The maximum number of fan
banks are operating and the
head pressure continues to
rise.
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When the CF-1000 goes into Split
Condenser, the CF-1000 closes the
Split Condenser Relay, closing
the split valve and shutting
power off to the split side fans,
and will automatically double the
number of fan banks previously
being run. When the CF-1000 comes
out of Split, the Split relay
will open, and the number of fan
banks being run will be halved.
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Ambient Temperature
Compensation of the Fan
Start/Stop Timing--The
CF-1000 will adjust the start and
stop timing of the condenser fan
s based upon the ambient
temperature. The CF-1000 will more
than likely start fans faster
when the ambient temperature is
warmer and will stop fans faster
when the ambient temperature is
cooler.
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Minimum Head Pressure
During Heat Reclaim--When
the CF-1000 detects the Heat
Reclaim relay is energized, the
CF-1000 will maintain a minimum head
pressure by reducing the number
of fan banks active and adjusting
the compressor staging.
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Minimum Head Pressure
During Gas Defrost--The
CF-1000 will maintain a minimum
head pressure by reducing the
number of fan banks active and
slowing the compressor staging.
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Fan Staging After Gas
Defrost--The CF-1000
will adjust the fan control
algorithm immediately following
the end of a gas defrost. The CF-1000
will anticipate the increase of
load due to the recovery time of
the defrost circuit.
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Parallel Mechanical
Backups--Backup pressure
controllers or thermostats are
wired in parallel with the CF-1000
Condenser Control Relays with
their power supply circuitry wired
through a time delay Condenser
Switchback Relay. If the CF-1000 were
to fail, the Condenser Switchback
Relay will de-energize, supplying
power to the backup controls. The
backup controls may be set as
closely to the Head Pressure
setpoint as possible.
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