| Features
The Wizard
WDC Defrost Control System is designed to
control the room or zone temperatures and the evaporator
operations for large ammonia and halocarbon
refrigeration systems. The WDC performs the functions of
the following independent control systems:
Evaporator Valve Group Status Monitor
Multi-Function Defrost Clock
Temperature Control
Temperature Monitoring and Alarming
Alarm System
Evaporator Valve Group
Status Monitor
The WDC has a series of status LEDs on the front panel
that provide an easy method to determine the status of
the Evaporator Valves and contactors.
Defrost Control
The WDC is an electronic control and time clock. The
time clock can operate up to 12 defrost cycles per day
with three separate defrost schedules as well as manual
defrost. The defrost can be either gas, electric, water
or off-time defrost. The WDC will cycle all valves
necessary to perform a defrost of some of the more
complex refrigeration systems.
During a defrost cycle the WDC will sequence through the
following cycles as required:
Hot Gas Defrost
Electric Defrost
Pumpdown Cycle
Pumpdown Cycle
SoftGas Cycle
Pre-Heat Cycle
Hot Gas Cycle
Main Electric Defrost Cycle
Drip Cycle
Drip Cycle
Equalizer Cycle
Equalizer Cycle
Fan Start Delay
Fan Start Delay
Water Defrost
Off-time Defrost
Pumpdown Cycle
Main Defrost Cycle
Water Stage1 Cycle
Main Water Defrost Cycle
Defrost Features
Daily Schedules.
The control has three unique
defrost schedules: Weekday (Monday - Friday), Saturday
and Sunday.
Automatically adjusts time for daylight savings.
The WDC can be set to automatically change the clock
for day light savings or can be set not to change if the
facility is in states where daylight savings is not
observed. The Daylight Savings Schedule is set through
2020.
Can schedule up to 12 defrost cycles per day.
The WDC can be programmed to run up to 12 defrost cycles
per day. The control will automatically space out each
cycle evenly or allow the user to program the start
times.
Gas, Electric, Water, or Air defrosts. The WDC
can operate defrost circuits that are either Off-time,
Hot Gas, or Electric. Steps that are not used can be set
to 0 minutes, and the controller will skip over them to
the next step.
Demand Defrost - Liquid Line Solenoid Feed Time.
The WDC can initiate its defrost cycles base upon
the total liquid feed time. This option can be used to
activate the system only when the "Number of Cycles per
Day" set to zero. The liquid demand delay can range from
0 to 24 hours, in fifteen minute increments.
Demand Defrost - Remote Activation
The WDC has a
digital input that forces the control into the defrost
cycle. This input can be used to activate the system for
an additional defrost cycle, or with the "Number of
Cycles per Day" set to zero, the input can be wired to a
gang defrost clock and a number of WDCs can be staged
evenly or to a frost sensor and the WDC will defrost
only when necessary.
Defrost Termination.
Any one of the following functions will terminate
the Main Defrost Cycle:
Clicks-On Thermodisk (Dry Contact).
By
providing a closure across the Defrost Termination
input terminal, the WDC will terminate the Defrost
Cycle. The Clicks-On should be mounted on the coil and
should have a temperature rating corresponding to
cleared coil temperature.
Suction Pressure Switch (Dry Contact).
By
providing a closure across the Defrost Termination
input terminal, the WDC will terminate the Defrost
Cycle. The pressure switch should be mounted on the
suction line and should be set to a suction pressure
corresponding to a cleared coil.
Termination Temperature Sensor.
The WDC will
monitor a temperature sensor mounted in the coil. The
WDC will terminate the Defrost Cycle when the
temperature exceeds a selectable Termination Setpoint.
Time.
If the WDC does not detect a termination
signal, the Main Defrost Cycle will terminate at the
end of the programmed cycle duration.
Defrost Termination Log. The WDC has a
"Defrost Log" that records the duration of the
previous 10 defrost cycle Defrost stages. This log can
be used to determine whether the current defrost setup
is operating efficiently or whether adjustments need
to be made
Temperature Control
Each WDC comes with a temperature sensor for monitoring
or controlling the temperature in the refrigerated room.
The control monitors for both high and low alarms each
having its own programmed delay when programmed. The WDC
will maintain the space temperature by cycling the LLS
based upon a Temperature Setpoint and a plus/minus
differential. The WDC will open the LLS when the
temperature reaches T = Setpoint minus Differential
Value. The WDC will close the LLS when the temperature
reaches T = Setpoint plus Differential Value.
Temperature Control Setback -- The WDC allows
the user to set a setback schedule, where the control
will operate the temperature control functions at a
higher setpoint during a specified time period. The
setback schedule has a Monday - Friday, a Saturday, and
a Sunday schedule.
Fan Cycling -- The WDC can cycle the evaporator
fans once the temperature within the space is met. The
WDC will also restart the fans after a setable delay to
prevent stratification of the air.
Temperature Alarming
The WDC can monitor three independent temperature
sensors, the Temperature Control Sensor, the Defrost
Termination Sensor, and an Auxiliary Temperature Sensor.
Temperature Control Sensor -- This sensor
consists of the the sensor used by the WDC for
temperature control. All alarming is disabled during
defrost. Once the WDC controller returns to normal
refrigeration, the alarm delays will begin as if the
sensor has just exceeded the alarm conditions.
Auxiliary Temperature Sensor -- This sensor is
an additional temperature sensor that is monitored and
logged, it does not control any WDC processes other
than alarming. The user can choose whether the alarms
are disabled during defrost or if the alarms are
active during defrost.
Defrost Termination Sensor --
This sensor
consists of the sensor used by the WDC to terminate
the defrost cycle based upon the coil temperature.
Should this temperature read above the setpoint level
of the termination setpoint for over 30 minutes, the
WDC will activate its systems alarms.
The WDC will activate its "System Alarm" relays when the
space temperature exceeds the Hi Temp Alarm Limit for a
duration longer than the Hi Alarm Delay or when the
space temperature goes below the Lo Temp Alarm Limit for
a duration longer than the Lo Alarm Delay. The WDC will
activate the System Alarm Relay based upon the following
alarm conditions:
High Alarm .
The space temperature must exceed
the High Alarm Limit for a time period longer than the
Hi Alarm delay. This function shall activate the
control's "System Alarm Relay 2".
Low Alarm .
The space temperature must be
below the Low Alarm Limit for a time period longer
than the Low Alarm delay. This function shall activate
the control's "System Alarm Relay 1".
Termination Temperature High Alarm.
The WDC
will activate alarms if the termination Click-On or
the Termination Temperature does not recover within 30
minutes. This function shall activate the control's
"System Alarm Relay 2".
Remote Communications
GenCom Communications allows the computer operator to
access the controllers within a facility via a PC. All
control programming and logging functions are accessible
and can be set or changed from the computer. The user
can view all text and data logs, make programming
changes to the controller, initiate defrost cycles, and
investigate alarm conditions.
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