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

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communications cable, the compressors will continue to function as two systems, one on each side of the break.
Each will have its own lead unit (Seq 1) and may have lag units (depending on how many controllers are on that side
of the break). Look for a cable break if there are multiple units with the same Sequence number displayed.
Each controller also monitors the communications data for errors. If these occur, the yellow advisory will come on,
and the controller displays a message to check the communications port. If this message comes on, and one
member changes to "AUTO" operation, then it has been mistakenly programmed with the same Unit Number as
another member. Refer to programming instructions above for instructions on programming.
Automatic rotation - A controller will be the lead compressor for the time programmed as TRANSFER INTERVAL.
Then it assigns itself the highest available rotation number. The lag compressors detect the loss of the lead unit and
decrement their rotation numbers. Number 2 becomes number 1, the new lead unit, number 3 becomes number 2,
etc. The former lead unit will become the last lag unit.
The transfer interval timer operates whenever a member is the lead (Seq 1) unit of the system. It will continue to time
out regardless of other units in the system. The remaining time is retained during power interruptions. It is reset back
to full value if the controller is in any mode other than Seq 1.
Other sequencing features - Any air system will exhibit pressure differences from one point to the next. Even a well
designed multi-compressor installation will show 'minor' pressure variations between one compressor's discharge
point and another compressor's discharge. These points will also vary from the actual system storage (normally the
air storage receiver). The controller sequencing system is designed to tolerate minor variations. The controller
sequencing system will automatically adjust the system setpoint to maintain the average system pressure.
Overpressures within any member compressor are prevented locally, and other members will load up to meet the
demand. When a TurnValve compressor is provided with current monitoring, the controller will also shed some load
on any overloaded unit, and lag units will load as required to service the demand. The dynamic setpoint control is
completely automatic and is continuously adjusted.
If airflow is restricted between the compressor units and the common storage, the 'minor' variations described above
become more significant. The pressure in the receiver will always be lower than that sensed by the compressor
system. The "AUTO SENTRY
®
-ES+" system will tolerate this, and will still maintain the average pressure within
limits. These restrictions will spread modulation over several units, rather than showing the strong preference to
unload the last loaded lag unit.
The Lag Start Delay timer of any member does not begin timing until the preceding member of the system is loaded.
This is particularly useful when starting up the system, as compressors will be started one at a time. This sequenced
starting also happens if the members are controlled by their remote inputs. If programmed for automatic restart after
power failure, the lead unit will be delayed by the automatic restart delay, then each additional unit will be delayed by
the lag start delay.