Filter
Top Products
6 – 6
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153
grayed out and hence, the user will not be able to op-
erate Pulldown feature. This is done to keep Pulldown &
Pumpdown features mutually exclusive.
Control Mode
This drop down box gives the operator the ability to
change the type of control mode such as suction pres-
sure control or process temperature control. The opera-
tor can also switch from setpoint 1 and setpoint 2 for
each control method. What is available in this dropdown
box is dependent on the number and type of control se-
lected in the confi guration screen.
Stop Load and Force Unload
The stop load and force unload feature’s primary pur-
pose is to attempt to prevent the compressor from
tripping off due to particular instrument reading. For
example, if the suction pressure drops too low, the com-
pressor will trip off for safety reasons. However, the stop
load & force unload algorithm recognizes a potential trip
and either stops the compressor from loading up or even
unloads the compressor to prevent the trip.
Stop load:
• When this value is reached, the capacity slide will not
advance in any condition.
Force Unload:
• When this value is reached, the capacity slide posi-
tion will decrease until the variable reading is below
this value.
High Motor Amps:
• Motor current values for stop load and force unload.
High Discharge Pressure:
• Discharge pressure value for stop load and force
unload.
Low Suction Pressure:
• Suction pressure values for stop load and force unload
Capacity Slide Triggered Outputs
The Vission 20/20 offers two digital outputs that can be
triggered at a specifi ed capacity slide position. By de-
fault, the outputs are preselected for economizer and
hot gas bypass. However, these preselected outputs are
customizable by the operator.
Slide Valve Setpoint:
• Operator editable labels for the each output.
Slide %:
• Indicates the capacity slide position where the digital
output is triggered.
State Below Setpoint:
• Defi nes the state of the digital output when the slide
position is below the “Slide %” setpoint. The operator
can choose between “N.O.” or “N.C.”
Active:
• Check box to enable the digital output.
Volume Slide Position Offset
These setpoints offer the ability to alter the Volume po-
sition table to take advantage of potential energy sav-
ings. Since the volume position is a function of the ca-
pacity position, the offset to the volume is based on the
position of the capacity slide. The volume offset can be
applied to the entire capacity slide range or just a por-
tion using the Capacity Range minimum and maximum
setpoints.
Volume Slide Adjustment %:
• The value in percentage of the volume slide offset.
Capacity Range:
• Defi nes the range that the volume position slide off-
set will be applied.
Soft Load
This setpoint is used to slow the loading of the compres-
sor. In some refrigeration systems, a loading compres-
sor can have dramatic effects on the system parameters.
This setpoint allows an operator to reduce the continu-
ous load pulse as defi ned in the proportional control sec-
tion to a percent duty cycle.
Soft load %:
• Defi nes the duty cycle of the continuous load pulse.
At 100%, the continuous pulse will truly be continu-
ous. At 50%, the continuous pulse would be reduced
to half time on and half time off in the time interval
defi ned in the proportional control section.
Section 6 • Compressor Control