Xylem 19-001-350R2 PACE Integrated Pump Controller Human Machine Interface (HMI) for the Silent Storm VFD Pumping System – Technician Guide - Manual (Page 22)

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helps the system to reach the setpoint faster, but at
the same time the system may overshoot the
setpoint very quickly since the PID does not have
enough time to react to the fast occurring changes.
A very low value will make the system take a lot of
time to reach the setpoint.
The values shown in figure 34 below have been
determined from empirical tests, and can be used
as defaults, but each system needs to be tuned, as
pumps and systems are different.
Low Flow (Proportional & Integral) denotes the PID
sensitivity on the first start of the first main.
Tap [Next] to move to the next Field Setup screen.
Figure 49: OPA, Ramp Up and Dp/Dt control
OPA Enable
This is a method used to shut down lag pumps
operating across-the-line in a system that uses both
VFD and XL (across-the-line) pumps. Check this
box to enable.
The overpressure accumulator measures the
overpressure, and calculates a value to addd to the
Overpressure Accumulator depending on this error
on each program scan. The system will shut off a
lag pump when “Trip Preset” is reached.
Min combo: Combo # on which, OPA is not desired
because it is desired that the last pump stop in
speed test.
Ramp Up:
Step (psi): During ramp-up, the # of psi the system
will step up. See “Step (sec)”. Normally set to 1 psi.
Step (sec): During Ramp Up, the time between
ramping the setpoint. Normally set to 4 sec.
dP/dT Control:
Enable (Checkbox): Controls whether the “dP/dT”
pump start/stop control functionality is utilized.
Check to utilize the rate of pressure drop when
starting/stopping pumps.
Start/Stop Inhibit : The rate at which the system
will inhibit pump starts or stops as the pressure rise
or drops during the decision process. Generally
0.5-1.0 is adequate to reduce pump cycling.
PM Skip: Controls how much pressure drop will
cause the system to automatically skip the PM
Pump in the sequence. Fast pressure drop
indicates a large demand has suddenly been
applied to the irrigation system. This is used to
detect the need to skip the small pressure
maintenance pump so that the main pump can
meet this demand as quickly as possible, avoiding
unnecessary pressure dips. Start with values at 1.0
and monitor. To disable this feature but continue to
use the Start/Stop inhibit system above, set this
value to 10 or greater.
dP/dT Inhibit(sec): After the main pump stops,
systems will often experience short pressure dips
that may cause the PM Skip system to restart the
main pump. Set this value to 20 seconds to prevent
the PM Skip process from restarting the main pump
within this period of time.
Current dP/dT values are shown to assist in
tuning the dP/dT system.
Combos
This screen allows you to configure various options
in a combo.
Select the maximum number of combos (up to
eight). For Combo 0, which is the ‘no pump’ combo,
all values except Overlap gray out. A brief
description of all parameters follows.
1. Delay Timer:
Start: number of seconds the station delays before
the start of the specified combo, once ∆P has been
reached
Stop: number of seconds the station delays before
it stops the specified combo, once ∆P has been
exceeded.
2. Normal Differential:
System is not in ‘Bypass’ mode.
Start: Start a specified combo when the difference
between the actual pressure and user defined SP
exceeds this value.
Stop: Stop a specified combo when the difference
between the actual pressure and user defined SP
exceeds this value.
3. Bypass Differential:
System is in VFD Bypass mode. Enabling bypass
for a particular VFD causes all pumps using that