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Soft Loading Time [Control Response]
Summary
Horizon chiller control (soft loading feature) ramps setpoint
changes. This provides a controlled transition during
machine startup and when setpoint changes are entered
during operation. Soft Loading along with solution pre-
heating are used to bring the chiller solution concentrations
and temperatures up to normal operating levels in a
controlled manner.
Details:
The control response set point can be adjusted within the
field startup settings menu group. The microprocessor
filtered control response determines how fast the machine
loads or unloads to a new setpoint target. This occurs at
startup and whenever an input setpoint is changed. Any
chilled water set point change entered into the CLD is
modified (FILTERED) to eliminate major upset of the
absorption solution cycle . The filtered setpoint can be
viewed by pressing "Enter" while viewing the setpoint
screen. This filtered setpoint is the actual target that the
control is proceeding towards. At the end of the soft load
time setting the filtered and setting values will be equal.
On startup, the filtered setpoint will be equal to the current
leaving water temperature. Soft load will slope the filtered
setpoint towards the active setpoint over the softload time
period. The Active setpoint will be reached at the end of the
filtered soft loading time (control response time) period.
See Figure 24.
Figure 24
CWS and target setpoint are
same before unit starts
Setpoint changed
because unit startup or
input changed
Softloading time is factory set to 15, but has an adjustment
range of 1 to 100 within the field startup group on the CLD
by service personnel at startup. This soft loading time will
affect how fast the Chilled Water; Heated Water and
Crystallization Margin internal setpoints reach their
respective targets. The filter is active at all the times and will
apply the time period to any setpoint change.
74
Front Panel CWS
Softload time duration
(time for new target setpoint to
reach new front panel setpoint.)
Filtered setpoint as a result
of soft load filtering.
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