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
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
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
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.
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.
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