Xylem 19 001 200 R2 SILENT STORM VFD Pumping System - Manual (Page 20)

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Override/Active switch: LDP Override
(Low Discharge Pressure fault disabled). If
initial system pressure is high enough,
place in Active.
VFD Bypass switch: Bypass
VFD Select switch: N/A
Speed Potentiometer: N/A
System control switch: AUTO
When done, place system control switch in
OFF. Return Override/Active switch to
ACTIVE.
The PM pump continues to charge the system
as in Automatic operation. Start and stop
sequence is based on pressure.
Once a demand for water exists, the PLC
starts the main pump with the lowest run time
as an XL (across- the-line) pump, based on
the “pressure below setpoint." If the flow
capacity of the main pump exceeds the
demand for water, pressure increases until the
PRV opens and discharges the excess flow
back into the water source. As demand for
water increases, the PRV closes. If the PRV is
completely closed, and the “pressure below
setpoint" drops low enough, the PLC brings on
the next Combo as required (all in XL mode).
The lead pump remains at full speed while the
next pump also comes up to full speed. If the
cumulative flow capacity of the main pumps in
operation exceeds the demand for water, the
PRV opens and discharges the excess flow
back into the water source. This process is
repeated for all available Combos.
Combo shutdown based on flow is made
possible by the way flow is read. The location
of the flow meter measures only the flow that
is actually being used. The flow out of the
PRV discharge that is returned into the water
source does not count as "measured flow."
The result is as demand for water decreases,
pressure continues to rise. The PRV opens as
required to maintain pressure. As more flow is
going out the PRV discharge, less flow is
actually being used. When the flow reading
drops below the “flow setpoint to stop” value,
the pumps shut down in the reverse order that
they started. Based on the demand for water,
this process continues until all main pumps
have shut down, and the station returns to
"System Charging" mode.
PLC Bypass Operation
Overview
This is an abnormal operating mode and
would be used if the PLC was not operable
and there is need to irrigate.
WARNING: PLC Bypass Hazard
This mode of operation should be used as a last
resort if there is no DSR, or it is not functioning
correctly. Constant operator attendance is
recommended when this mode is used. The water
demand must be calculated to match the
individual pump output as closely as possible.
Failure to do so will cause a serious over-pressure
condition. The high pressure discharge safety
does not function in PLC bypass, and damage to
your piping could occur. The only safeties that
function in PLC bypass are low discharge
pressure and phase fault.
Failure to follow these instructions could result in
serious personal injury, death, or property
damage.
System Operation (performed in order)
System control switch: OFF
All Individual Pump switches: OFF
Override: LDP Override (Low Discharge
Pressure fault disabled). If initial system
pressure is high enough, place in Active
VFD Bypass switch: NA
VFD Select switch: NA
Speed Potentiometer: N/A
PLC Bypass switch: BYPASS
System control switch: MANUAL
Pump 1 switch: ON
Allow system pressure to stabilize before
turning on additional pumps.
Pump 2 switch: ON (if required)
Pump 3 switch: ON (if required)
NOTE: When done, turn OFF all pump
switches and place system control switch
in OFF. Return Override/Active switch to
ACTIVE.