Ingersoll-Rand 100-200 HP/75-160 KW - Manual (Page 45)

5.8 CAPACITY CONTROL (Continued)
MODULATION/ACS CONTROL (Continued)
The automatic control selector (ACS) is designed to
continuously monitor the plant air demand and select
either the on-off line, or the modulate control mode -
whichever is most desirable at any time during an
operating day.
It allows the compressor to operate in its most efficient
mode without attendance, thereby reducing power costs
to a minimum.
When the compressor operates in the on-off line control
mode, the length of time the compressor remains in the
“off line” condition is an indication of the plant air
demand. Intellisys controller is sensing and awaiting a
sufficient line pressure decrease before signaling a shift
to the on line mode. If the “off line” time period is
relatively short, thereby indicating a high demand for air,
it is preferable to shift the control system to upper range
modulation.
The Intellisys does this, and does it automatically if the
compressor unloads 3 times within a 3 minute time
period.
If later, the plant demand decreases, and even under
modulate control the line pressure reaches the setting of
the Intellisys controller and the control shifts to the “off
line” mode, the time in this mode will still be monitored. A
long “off line” time period indicates a low plant air
demand, indicating the desirability of operating in the
on-off line mode.
The Intellisys then does this, and does it automatically if
the compressor operates unloaded for more than 3
minutes.
MODULATION ONLY
If MODULATION ONLY is turned on in the set point
routine, the unit will shift to Modulation control mode
immediately when the unit is running. The 3 cycles within
3 minutes time period required for ACS to change to
Modulation mode is bypassed. The unit will stay in
Modulation mode until the UNLOAD button is pressed or
the Mode of Operation set point is changed.
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5.9 AUTOMATIC START/STOP CONTROL
Many plant air systems have widely varying air demands
or large air storage capacity which allows for automatic
standby air capacity control.
During periods of low air demand, if the line pressure
rises to the upper set point, the Intellisys begins to time
out. If the line pressure remains above the lower set point
for as long as the set time, the compressor will stop. At
the same time the display will indicate the compressor
has shut down automatically and will restart
automatically. An automatic restart will occur when the
line pressure drops to the lower set point.
The upper and lower set points and shutdown delay time
are set on the Intellisys control panel. There is a 10
second delay after shutdown during which the
compressor will not restart even if line air pressure drops
below the lower set point. This is to allow the motor to
come to a complete stop and the Intellisys controller to
collect current data of operating condition. If line air
pressure is below the lower set point at the end of 10
seconds, the unit will start unless the load delay timer is
set greater than 10 seconds.
Auto Restart Delay
This is the number of seconds the line pressure must
remain below the online set point before the compressor
will start if it was stopped due to an auto start/stop
situation. This timer will not delay an auto restart if the
time is set to 0.
Automatic Start/Stop Operation
When in operation, the compressor must meet two
specific timing intervals before the Intellisys controller will
stop the unit in an Automatic Start/Stop situation.
For this discussion, the timers will be called timer “A” and
timer “B”.
FIRST
Timer “A” prevents the compressor from automatically
starting more than 6 times an hour by requiring the unit
to run at least 10 minutes after each automatic start.
This 10 minute run period can be loaded, unloaded or a
combination of the two and allows dissipation of heat
generated within the motor windings at start.