18
OM
AGSB-5
•
Soft Load – (ON/OFF)
•
Begin Capacity Limit – (Unit %)
•
Soft Load Ramp – (seconds)
The Soft Load Unit Limit increases linearly from the Begin Capacity Limit set-point to
100%, over the amount of time specified by the Soft Load Ramp set-point. If the option is
turned off, the soft load limit is set to 100%.
Demand Limit
The maximum unit capacity can be limited by a 4 to 20 mA signal on the Demand Limit
analog input. This function is only enabled if the Demand Limit setpoint is set to ON. The
maximum unit capacity changes linearly from 0% (at 20 mA) to the 100% (at 0 mA).
Network Limit
The maximum slide load percentage of the compressor can be limited by a value sent
through a BAS network connection and stored in the Network Limit variable. This function
will be enabled if the control source is set to BAS.
ICE Mode Start Delay
In ICE mode there is a 12 hour delay from the time the unit shuts off until it may start again.
If the chiller is in ICE mode and the delay is active, the unit state will be Off and the unit
status will indicate this condition. The time left will also be displayed. While this delay is
active, the chiller may still start in cool mode.
If needed, the ice delay can be cleared using a setting found in the unit set points menu.
Pumpdown
When a circuit reaches a condition where the compressor needs to shut down normally, a
pumpdown will be performed. The slide target will automatically go to 0 while pumping
down, and the compressor will run until the pumpdown pressure has been reached, or the
pumpdown time has been exceeded. The Pumpdown Setpoint may need to be reduced if the
unit is running in the COOL w/ GLYCOL mode.
Service Pumpdown
If the option for a service pumpdown is enabled, then on the next pumpdown the pressure
setpoint will be 15 psi. The circuit will pumpdown to this pressure and shut off. When the
compressor has completed the service pumpdown, the setpoint is reset to No.
Manual Slide Control Mode
The slide position on each circuit can 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%.
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 Positioning
Slide Load Indicator
Each compressor will estimate its slide load percentage from the present value of the slide
load indicator. The percentage is based on the 4-20mA signal from the slide load indicator.
See Table 6 on page 13 for the mA signal corresponding to slide position.
Summary of Contents for AGS 206A
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