Emerson Vission 20/20 Operation And Service Manual page 201

Appendix B • Vission 20/20 Application Procedures
Both Process Temp
Pressure Control must both be enabled from the
Confi guration screen to do this.
Modbus Register 40503 - Auto Capacity Control
Type
0 = Suction Pressure (if enabled from Confi guration
screen)
1 = Process Temp (if enabled from Confi guration
screen)
2 = Discharge Pressure (if enabled from Confi guration
screen)
Compressor Start and Stop Commands
Modbus Register 40508 - Start Command
1 = Start Compressor Command
Four (4) minute Remote mode time-out timer
• Once the compressor has been started using the
Start Command, a 4 minute timer will start. If no
further communication takes place to the 20/20
within 4 minutes, the 20/20 will be placed in Local
Auto mode, a yellow banner will be displayed on the
20/20 signifying that a "Remote Comm Time-out"
occurred, and the Event List will get populated with
a time-stamped "Remote Comm Time-out" event.
Modbus Register 40509 - Stop Command
1 = Stop Compressor Command
• Vission 20/20 panel will remain in Remote (Idle)
mode after a Stop Compressor command has been
issued.
Remote Control via Direct I/O (Hard-wired)
Remote Control of the compressor can also be accom-
plished using hard-wired inputs. These include Remote
Start-Stop digital input, Remote Increase Capacity digi-
tal input, Remote Decrease Capacity digital input, and
Remote Caphold Setpoint analog input. For communi-
cation register information, refer to Table B-4.
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 2.0
NOTE
Control and Suction
Confi guration Screen Setup:
(Reference the "Communication" section of Figure B-24)
For Direct I/O control:
• Confi gure "Active Remote Control" drop-down box
to "Direct I/O". This selection activates the Remote
Start-Stop digital input. This is the ONLY selection
that activates the Remote Start-Stop digital input.
• Below "Active Remote Control" selection box, check
the "Direct I/O"" box.
A popup "Direct I/O Control Type" box now appears.
• From the popup "Direct I/O Control Type" box,
select desired control method:
• Auto Capacity
• (Digital) Manual Capacity – comp. capacity con-
trolled via digital increase and decrease inputs.
• (4-20mA) Capacity Hold – compressor capacity
controlled via Remote Caphold analog input.
Auto Capacity
• The compressor is started and stopped from the
Remote Start/Stop input, but the compressor capac-
ity is controlled from the internal compressor con-
trol setpoints entered in the 20/20. The Auto-cycle
setpoints can be enabled or disabled as desired.
(Digital) Manual Capacity
• The compressor started and stopped from the
Remote Start/Stop input, but the compressor capac-
ity is controlled from the Remote Capacity Increase
and Remote Capacity Decrease digital inputs.
(4-20mA) Capacity Hold
• The compressor started and stopped from the
Remote Start/Stop input, but the compressor capac-
ity is controlled from a 4-20mA analog signal run to
20/20. The 4-20ma signal will be proportional to
0-100% capacity hold value. For instance, 4mA = 0
percent, 12mA = 50%, and 20mA = 100%.
Hold Capacity Operation
• The Capacity Hold analog signal defi nes a "target"
capacity slide valve position for the compressor. The
20/20 will position the capacity slide to the "target"
position. rules of this capacity hold algorithm are;
1. If the new target is < 0.4% (full scale) away from the
current position – then don't do anything – this is
the deadband region.
2. If new target is > deadband region but < 10% (full
B - 45