OM AGSD-1
45
The load output will be pulsed on for 100ms when either of the following conditions are
true:
•
Slide Change <= 0 AND Slide Position < Slide Lower Limit
•
Slide Position < Slide Lower Limit – 10%
The unload output will be pulsed on for 300ms when either of the following conditions are
true:
•
Slide Change >= 0 AND Slide Position > Slide Upper Limit
•
Slide Position > Slide Upper Limit + 10%
Manual Slide Control Mode
The slide position on each circuit may be controlled manually. A setting on the compressor
setpoints screen in each circuit controller allows the operator to select manual slide control.
On the same screen, a slide target can be selected, from 0% to 100%. Manual slide control
can be selected whether the compressor is running or not.
Anytime a circuit is in manual slide control, it is considered to be at full load in the staging
logic. It also will not be considered a running compressor for load balancing purposes.
None of the capacity limits outlined above will apply in manual slide control, but all stop
alarms are still applicable.
Slide control will revert back to automatic control if a stop alarm occurs while the
compressor is running, or the slide control has been manual for four hours.
Condenser Fan Control
The compressor must be running in order to stage fans on. All running fans will turn off
when compressor goes to the off state.
Saturated Condenser Temperature Target
The condenser fan control logic will attempt to control the saturated condenser temperature
to a calculated target. A base condenser target is calculated based on evaporator saturated
temperature. The equation is:
Base saturated condenser target = 5/6 (saturated evaporator temperature) + 68 1/3
This value is then limited to a maximum and minimum determined by the condenser target
max and min setpoints. If these setpoints are both set to the same value, then the saturated
condenser temperature target will be locked at that value.
VFD (Optional)
Condenser pressure trim control is accomplished using an optional VFD on one fan. This
VFD control uses a proportional integral function to drive the saturated condenser
temperature to a target value by changing the fan speed. The target value is normally the
same as the saturated condenser temperature target setpoint.
VFD State
The VFD will be started when
all
the following conditions are true:
•
Compressor State is not Off
•
Fan VFD is enabled
•
Saturated Condenser Temp >= Saturated Condenser Temp Target
•
Fan speed output = 0
The VFD will be turned off when
either
of the following conditions are true:
Summary of Contents for AGS 225D
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