Gardner Denver AUTO SENTRY-ES+, Operating And Service Manual

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ESTABLISHING THE INITIAL SEQUENCE
The first member compressor placed into sequence mode will become the lead unit. However, since any controller
first placed into sequence has no way of knowing whether or not other members already exist, it will first assume the
highest rotation number available. For example if the number of units to be sequenced is programmed at four, any
compressor will start out in position four when placed in sequence mode. It will then listen for other units on the
communications line.
If there is no member with the next lower sequence number, the controller will automatically promote itself. This
movement is fairly rapid with the controller, and the number will advance to the lowest vacant position in several
seconds.
To establish a desired order of units, press [STOP/RESET] or select any mode other than SEQUENCE (if already in
sequence, put into auto mode if you wish to continue operation while doing this selection). Then put the desired lead
unit back into sequence. Wait until it promotes one step (or longer), then put the desired #2 unit into sequence mode
and wait until it promotes one step, and so forth until all units are back into the sequence mode.
During this procedure, the system is not deprived of air. This is due to one of the outstanding features of the
controller sequencing system: control is always executed locally by each member controller. So while controllers
count down towards the final order, they are also capable operating their compressor and will deliver air. Once the
sequence order is finally established, setpoints will continue to be adjusted in each member to provide operation in
the preferred order. This may take several minutes after a manual change of sequence numbers.
"AUTO SENTRY
®
-ES+" SEQUENCE SYSTEM OPERATION
Each member compressor in the system operates similarly to the Automatic mode of operation. It will start, load,
modulate, unload, blowdown, and automatically stop as necessary to meet system demand for air. There are several
differences, however, when running in the Sequence mode.
The pressure shown on the top line of the display is the average system pressure of all the members. Each member
communicates its local pressure through the communications cable, for use by others in the system for display and
control. The system responds to this average. This number will be the same for all units in the system. To obtain
the local package discharge pressure, select the
"DIS PRESS" alternate display on the lower line.
Pressure setpoints are continuously adjusted, depending on the operation of the members. The last lag unit which is
loaded will control its modulation to keep the system pressure near the programmed Set Pressure, and serves as the
trim machine. Any running lead unit will be adjusted for slightly higher pressures, and will run at or near capacity.
The first unloaded lag unit will have its reset pressure adjusted so it will come on line if the system pressure drops to
the programmed Reset Pressure. The system is continuously adjusted to maintain the system pressure between the
programmed Set and Reset Pressures.
If any lag unit is loaded, any preceding lead unit will be loaded. Its blowdown timer will reset and hold at full value.
This ensures that the last lag unit will always be the first to unload and blow down, and lead units will be prepared to
handle the demand.
When demand exceeds the capacity of the loaded lead compressor(s), the pressure will drop. If a lag unit is stopped,
its restart will be delayed. This delay is the adjustable "Lag Start Delay". This allows time for lead units and stored
air to serve intermittent demands, without starting another compressor. The next available member accumulates any
time spent below Reset Pressure, and will start whether there are repeated brief demands or a sustained demand.
The Lag Start Delay timer does not begin timing until the preceding member of the system is loaded.
SEQUENCED SYSTEM CHECKOUT
One of the best indicators of the stability of the system is to compare the local system pressure of a running unit with
the system average pressure. To do this, simply press the [<] or [>] cursor keys until the lower line of the display
shows DIS PRES and the local pressure. In a properly operating system, this value will be within 1-2 psi of the top
line value, and will change slowly as demand and delivery are changing. Rapid and large changes in local pressure
indicate system problems. Ensure that all compressor units are piped to a common system pressure with adequate
storage to handle the plant demands. Select other operating modes if rapid response to large demand changes is
needed.
The system is redundant, and will tolerate any breakdown in communications. If any unit is taken out of the
Sequence mode, other members will "fill the gap" to keep the system operating. If a break should occur in the