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

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13-9-653 Page 2
Constant run mode operation - This mode is best used in applications where there are no long periods of unloaded
operation, or for minimum response time to sudden demands. The compressor unit will start and run continuously,
using its modulation controls to match delivery to demand.
As demand falls below the compressor capacity, the pressure will rise to the setpoint of the control. When the
pressure reaches the setpoint, the controller operates the solenoid valves TVO (TurnValve open), TVC (TurnValve
close), IVO (inlet valve open) and IVC (inlet valve close) to control the CFM of the compressor to match the CFM
demand of the air system. As the demand changes, the controller will continue adjustment for the best compressor
operation. At moderate to heavy demand, the inlet will be held open, and the TurnValve will control delivery. At
lighter demands, the TurnValve will be fully open, and the inlet valve will control capacity. At very light demand, the
compressor will unload, but will not blow down the reservoir. It will reload just below the set pressure. The controller
will thus maintain the pressure within a few psi of the set pressure.
On compressor units without TurnValve, the controller operates valves IVO and IVC to position the inlet valve. This
continuously adjusts delivery to match demand.
If the controller is programmed for "load-unload" operation, the controller will deliver full capacity until the system
pressure reaches the set pressure. It will then unload (but not blow down) and will not deliver any air to the system.
When the system pressure falls to halfway between the set and reset pressure the controller again fully loads the
compressor.
When first starting, the controller will keep the compressor fully unloaded and blown down until the system pressure
drops below the reset pressure. Once loaded, the reservoir will remain fully charged, regardless of demand.
Responses to demand are thus immediate, as soon as system pressure drops below the setpoint.
Low demand mode operation - The low demand mode reduces power consumption by relieving pressure in the
reservoir during unloaded operation. This mode is best used where there is moderate air storage and there are
unloaded periods during the day, but frequent motor starting and stopping is undesirable. During periods of moderate
to high demands, this mode is identical to the constant-run mode described above.
During low demand periods, the controller will open the blowdown valve and fully close the inlet valve to minimize the
motor load. A timer is reset when this occurs. While in this state, control air pressure is supplied from the plant air
system (as are any plant loads). When the system air pressure drops to the reset pressure due to increased
demand, the blowdown valve recloses and the controls resume their normal modulation to maintain the system
pressure near the set pressure.
Subsequent blowdown periods are not allowed until the timer has completed its cycle. This cycle eliminates frequent
blowdowns during moderate loads, and the energy required to repressurize the reservoir. It also eliminates the
problems of oil foaming and carryover that can occur if the oil reservoir of an oil-flooded compressor is blown down
too often. The timer is adjustable from 1 to 20 minutes.
Automatic mode operation - This mode provides automatic start and timed stop, and is best used in applications
with long unloaded periods (e.g. idle shifts or weekends) and adequate storage to allow the compressor to be
stopped for periods of light demands. Operation during periods of moderate to heavy demands are identical to the
low demand mode.
The automatic time delay is adjustable from 1 to 20 minutes. If the controller operates unloaded for this period with
no demand, the compressor drive motor is halted to eliminate its power consumption. The controls will remain in this
state until demand is again indicated by a drop in pressure.
This is the most common selected mode of operation, as it automatically will operate the compressor unit in the most
efficient manner for the demand of the air system.
Sequence mode operation - This mode provides for communication between controllers, operating only as many as
are required for economical operation. This is best used on applications with large storage capacity and diverse
loads. The lead unit will operate identically to the automatic mode; operation will be automatically staged for each lag
unit (up to 8 total). For more information, refer to the sequencing instructions later in this chapter.
Communication between controllers is achieved by interconnection of a communications cable to circuit board
connectors. A "unit number" must be assigned to each unit in this mode, but the display will indicate the unit's actual
operating ranking.