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Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153
Condenser Press:
• This is the read only parameter and it displays the
present value of condenser pressure.
Condenser Setpoint:
• This is the condenser pressure setpoint that needs to
be maintained.
Upper Deadband:
• This is the condenser pressure setpoint upper dead-
band value. No additional condenser capacity is add-
ed when the condenser is selected for automatic step
control and the condenser pressure falls within this
deadband.
Lower Deadband:
• This is the condenser pressure setpoint lower dead-
band value. Condenser capacity is not reduced
when the condenser is selected for automatic step
control and the condenser pressure falls within this
deadband.
Ambient Temp:
• This is the read only parameter and it displays the
present value of ambient temperature. This is dis-
played only when Ambient Sensor is enabled from
Confi guration Screen.
Wetbulb Temp:
• This is the read only parameter and it displays the
present value of wetbulb temperature. This is dis-
played only when Wetbulb Sensor is enabled from
Confi guration Screen.
Wetbulb Offset:
• This is the offset value from wetbulb temperature as
the override point.
Switch Temp:
• This is the ambient temperature setpoint used for au-
tomatic switching of profi le from summer to winter
and vice-versa.
Profi le Selection:
• Profi le selection allows operator to have two different
output profi les for summer and winter. Operator can
have different selection of fans, pumps & VFD in fi ve
steps of step control table. Different profi les allow
inclusion/exclusion of water pumps in cold weather
when summer/winter auto switch is enabled. This
selection is inactive when Run mode is Auto and
Summer/Winter Auto Switch is enabled.
High to Low Speed Fan Delay:
• This is a time delay for the fan spin down in case of
2- speed motor/dual speed fan.
Summer/Winter Auto Switch:
• This checkbox when enabled allows profi les to switch
automatically depending on ambient temperature
setpoint when Run Mode is “Auto”. When ambient
temperature falls below ambient temperature set-
point, winter profi le is used. Similarly when ambient
temperature is above ambient temperature setpoint,
summer profi le is used.
Wetbulb Override:
• This checkbox when enabled gives the operator a
functionality to control energy wastage. When the
condenser temperature reaches wetbulb tempera-
ture plus the operator given offset, then the con-
denser control operation does not add additional
steps. This is done as it is not possible to lower the
temperature anymore, and by adding more fans or
pumps controls the operation by manually stepping
using an on/off toggle button at each step.
Step Control
The Step Control allows the operator to setup the man-
ner in which Fans, Pumps & VFD will be turned on/off.
Fans & Pumps are connected on digital outputs Out #1
to Out #4. VFD Fan is connected on Analog Output. Each
step can have maximum of fi ve outputs connected to it.
Each step can be opted in or out depending on enabling
of checkbox, see Figure 11-2. Step Control Screen.
When Run Mode is Auto and condenser pressure rises
above upper deadband, condenser step gets incremen-
tal from Step 1 to Step 5 and hence switching on/off
Pumps, Fans & VFD connected on outputs. This holds
true for decremented of steps from Step 5 to Step 1
when condenser pressure falls below lower deadband.
Step Delay:
• Allows operator to set time delays between condens-
er steps. Condenser Pressure must be outside upper
or lower deadband continuously for delay time in or-
der to increase or decrease condenser steps. While
in a VFD step, an additional step can only be added
once VFD has reached its maximum speed setpoint
and the delay timers are satisfi ed.
• Similarly in a VFD step, a step can only be removed
once VFD has reached its minimum speed setpoint
and the delay timers are satisfi ed. Step Delay acts
as “ON” timer while loading and acts as “OFF” timer
while unloading for the same step.
Low Speed Fan:
• Allows steps to have option for time delay in case
of fan spin down. Any of Out #1 to Out #4 can be
Section 11 • Condenser Control