Step Control - Emerson Vilter Vission 20/20 Operation And Service Manual

Section 11 • Condenser Control
Manual:
• Mode for controlling condenser operation manually.
Operator controls the operation by manual stepping
using an on/off toggle button at each step.
Condenser Press:
• This is a read only parameter and it displays the pres-
ent 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 a read-only parameter and it displays the
present value of ambient temperature. This is dis-
played only when Ambient Sensor is enabled from
Configuration Screen.
Wetbulb Temp:
• This is a read-only parameter and it displays the
present value of wetbulb temperature. This is dis-
played only when Wetbulb Sensor is enabled from
Configuration 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 profile from summer to winter
and vice-versa.
Profile Selection:
• Profile selection allows operator to have two different
output profiles for summer and winter. Operator can
have different selection of fans, pumps & VFD in five
steps of step control table. Different profiles 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.
11 – 2
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 profiles to
switch automatically depending on the ambient
temperature setpoint when Run Mode is "Auto".
When ambient temperature falls below the ambient
temperature setpoint, winter profile is used. Similarly
when ambient temperature is above the ambient
temperature setpoint, summer profile 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 a maximum of five outputs connected to
it. Each step can be opted in or out depending on en-
abling of checkbox.
When Run Mode is Auto and condenser pressure rises
above the upper deadband, the condenser step incre-
ments from Step 1 up to Step 5 and hence switching on/
off Pumps, Fans & VFD connected on outputs. This holds
true when decreasing steps from Step 5 to Step 1 when
condenser pressure falls below the 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 satisfied.
• Similarly in a VFD step, a step can only be removed
once VFD has reached its minimum speed setpoint
and the delay timers are satisfied. Step Delay acts
as "ON" timer while loading and acts as "OFF" timer
Vission 20/20 • Operation and Service Manual • Emerson • 35391SC 2.7