| Features
The WCFC is the most
advanced condenser system controller in the industry
today. The control will efficiently cycle up to seven
fan banks or six fan banks with split condenser,
controlling the discharge pressure effectively.
The WCFC was
engineered to meet the two main variations in systems
today; fixed head and floating head. The Fixed head
control will sequence fans based on discharge pressure,
while floating head control will sequence fans based on
discharge pressure and liquid temperature.
The control has a 10
character alphanumeric vacuum fluorescent display, four
input keys, integrated input terminals and output relays
on a single P.C. Board. The compact design makes this
Control very reliable. It is designed to operate from
-30°F to 150°F ambient temperature. Menu driven software
eases operating parameter changes and setting
adjustments.
The WCFC was
engineered to meet the two main variations in systems
today; fixed head & floating head. The fixed head
control will sequence fans based solely on discharge
pressure with optional ambient temperature sensors to
optimize the fan cycling speed. Floating head control
will sequence fans based on discharge pressure and
liquid temperature.
Sequential Staging --
The
WCFC 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 WCFC will
keep the first fan bank running
nearly constantly to prevent
expansion and contraction at the
pipe and tube sheet joints.
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 on the
WCFC Condenser Board.
Fixed Head Pressure
Control -- The WCFC
can stage the condenser fan banks
based upon a fixed head pressure setpoint.
For fixed head
operation, the controlling parameter is discharge
pressure with an ambient temperature sensor to
optimize the fan cycling speed. The set point
for discharge pressure is user definable in the
system menu and is modified when defrost or heat
reclaim is turned on. The condenser fan control will
cycle fans on at a point 5% above this set point,
and cycle fans off 2.5% below this set point. This
will maintain the average discharge pressure at the
set point pressure.
Example: Setpoint =185
psig
Cut-in =185 +5% =194 psig
Cut-out =185 -2,5% =180
psig
Floating Head
Pressure Control -- The
WCFC can stage the condenser fan
banks based upon the temperature of
the liquid drop leg temperature and
ambient temperature. The WCFC
will maintain the liquid at the
Ambient Sub Cooled Refrigerant Setpoint.
For floating head control,
all setpoints are internally calculated based on the
setting. It is labeled T OFFSET (Condenser Temperature
Offset) and is located in the SYSTEM menu. The liquid
line temperature setpoint is equal to ambient
temperature plus the condenser offset temperature. The
condenser offset temperature is adjustable from 6 - 25
deg F. The effect of this setting is the amount of
subcooling the Condenser control will maintain. A lower
offset value will tend to increase the amount of
subcooling.
Example: Ambient
Temperature =80 deg F
Condenser Offset =10 deg F
Liquid Temperature Set
Point =80 +10 =90 deg F
The range of the liquid
temperature set point is 40 - 100 deg F. If the
calculation method had a liquid temperature set point
below 40 deg F, the control will default to 40 deg F,
and if the calculation exceeds 100 deg F, the control
will default to 100 deg F. The discharge pressure
setpoint is determined from a saturation curve.
Different refrigerants have different saturation curves.
The range of the discharge pressure setpoint is 148 psig
- 250 psig for R-502 for example.
The fans are cycled first
according to the head pressure. Once the head pressure
is satisfied, the fans are cycled by the liquid line
temperature. In order to obtain optimal sub-cooling to
the liquid refrigerant, the flooding valve in the rack
should be set 5 lbs below the minimum (flooding) head
pressure setpoint.
The defrost status adjusts
the discharge pressure setpoint according to the minimum
defrost head pressure setpoint that can be adjusted in
the System menu. Set the minimum defrost head pressure
setpoint lower than standard setpoint, or zero if
boosting pressing is not needed. The heat reclaim status
adjusts the discharge pressure setpoint according to the
minimum heat reclaim head pressure setpoint that can be
adjusted in the System menu. Set the minimum heat
reclaim pressure setpoint lower than standard setpoint,
or zero if boosting pressing is not needed.
Split Condenser --
The
WCFC will attempt to maintain
the condenser in its smallest
configuration. If the WCFC
can maintain the head pressure
while in the "split
condenser" mode even though
the ambient temperature is above
70 °F, the WCFC will do so. The
WCFC will lock into the Split
mode when the ambient temperature
is below a setable ambient
temperature Setpoint. The WCFC
will only come out of split
condenser when the following
occurs:
When the WCFC goes into Split
Condenser, the WCFC 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 WCFC
comes out of Split, the Split
relay will open, and the number
of fan banks being run will be
halved.
Ambient Temperature
Compensation of the Fan
Start/Stop Timing -- The
WCFC will adjust the start and
stop timing of the condenser fans based upon the ambient
temperature. The WCFC will more
than likely start fans faster
when the ambient temperature is
warmer and will stop fans faster
when the ambient temperature is
cooler.
Minimum Head Pressure
During Heat Reclaim -- When
the WCFC detects the Heat
Reclaim relay is energized, the WCFC will maintain a minimum head
pressure by reducing the number
of fan banks active and adjusting
the compressor staging.
Minimum Head Pressure
During Gas Defrost -- The
WCFC will maintain a minimum
head pressure by reducing the
number of fan banks active and
slowing the compressor staging.
Fan Staging After Gas
Defrost -- The WCFC
will adjust the fan control
algorithm immediately following
the end of a gas defrost. The WCFC
will anticipate the increase of
load due to the recovery time of
the defrost circuit.
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