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Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153
monitor compressor load. If Suction pressure / pro-
cess temperature goes beyond Load Rate 1 setpoint
offset then sequencing decisions are made according
to Load Rate 1 timer.
Suction Pressure/Process Temperature Control Setpoint:
• The target setpoints are read only values here.
These setpoints can be changed by logging on to
“Compressor Control” Screen.
Unload Rate 1 Offset (inner):
• Defi nes the inner pressure/temp setpoint to moni-
tor compressor load. If Suction Pressure/Process
Temperature Control drops below Unload Rate 1 set-
point offset then sequencing decisions are made ac-
cording to Unload Rate 1 timer.
Unload Rate 2 Offset (outer):
• Defi nes the outer Pressure/Temp setpoint offset
to monitor compressor load. If Suction Pressure/
Process Temperature drops below Unload Rate 1
offset and goes below Unload Rate 2 setpoint offset,
then sequencing decisions are made according to
Unload Rate 2 timer.
Capacity Load/Unload Timers:
• One of the following Capacity Load/Unload rate
timers are used to make sequencing decisions peri-
odically. Suction Pressure/Process Temperature set-
points are monitored to identify which one of the fol-
lowing timers to be used.
Load Rate 1 (Inner):
• If Suction Pressure/Process Temperature goes be-
yond Load Rate 1 setpoint offset then Load Rate 1
timer is used to make periodic sequencing decisions.
Load Rate 2 (Outer):
• If Suction Pressure/Process Temperature surpasses
Load Rate 1 offset and goes beyond Load Rate 2 set-
point offset then Load Rate 2 timer is used to make
periodic sequencing decisions.
Unload Rate 1 (Inner):
• If Suction Pressure/Process Temperature goes below
Unload Rate 1 setpoint offset then Unload Rate 1
timer is used to make periodic sequencing decisions.
Unload Rate 2 (Outer):
• If Suction Pressure/Process Temperature surpasses
Unload Rate 1 offset and goes below Unload Rate 2
setpoint offset then Unload Rate 2 timer is used to
make periodic sequencing decisions.
Compressor Sequencing Table:
• Compressor sequencing table menu allows operator
to view and adjust settings those are used for com-
pressor sequencing.
Equipment:
• Options of this combo box are updated automatical-
ly. This contains names of all the compressors in the
network communicating with Master compressor.
Equipment name can be selected from drop-down
list. Same Equipment name should not be confi gured
more than once in Sequencing table.
Control:
• Inclusion/exclusion of compressor partaking in the
sequencing can be decided on basis of this toggle
button. Compressors can be included/excluded by
toggling ON/OFF.
NOTE
Switching a compressor control to OFF when running
in auto seq mode puts respective slave compressor
into local auto mode. This feature is used to add or
remove slave compressors to sequence table when
running in auto sequence mode.
CFM:
• CFM column is read only. These values are updat-
ed automatically when Equipment combo box is
changed. This indicates Slave compressor capacity in
CFM.
Priority:
• This defi nes priorities of compressors on the network.
This priority will decide the sequence in which com-
pressors will be turned on and off during sequence
cycle. Lower the priority number greater the priority
of the compressor.
Step:
• This parameter would decide stepwise increment or
decrement value in percentage of the compressor
capacity. In the case when last step makes total ca-
pacity greater than maximum capacity, total capac-
ity will get reduced to maximum capacity. Same is
applicable when last step makes total capacity lower
than minimum capacity takes priority.
Min Cap:
• Defi nes the lowest capacity in percentage with which
a compressor is allowed to run. Minimum capacity
value takes preference on fi rst step value.
Max Cap:
• Defi nes the highest capacity in percentage with
which a compressor is allowed to run. Maximum ca-
pacity value takes preference over last step value.
Machine Start Time:
• Machine start timer shows the time in seconds that
the Master Compressor will hold before starting slave
compressor once (Start) decision is taken.
Section 10 • Compressor Sequencing