NO
YES
6.1 Theory of Operation — SINGLE PUMP
The system is designed to maintain the discharge Pressure
Setpoint.
A pump is turned on when the system pressure drops to the Wake-
Up Setpoint (Wake PSI), a specific amount of pressure below the
pressure setpoint.
A variable frequency drive (VFD) will operate the pump so that the
pressure setpoint is constantly maintained—slowing it down and
speeding it up as needed to meet fluctuating demands.
The pump will stop (enter sleep mode) when the system pressure
setpoint is reached and demand stops. Demand is measured by
using either the flow rate or the pump speed (indicated by VFD
frequency).
Additional Automation Features:
Automatic Filter Controls
• The controller will signal the filter flush valve to open based
on a signal from a PSID switch. There are also timer based
and manual filter flush controls.
• Automatically operated intake screen supply valve.
Remote Start
In addition to starting on pressure drop, the system can also start
via a remote signal from an external source, such as an irrigation
controller. The system will then operate automatically to maintain
the PSI Setpoint.
System Protections
The system will automatically Fault (shut-down) to protect the
system from the following occurrences:
• Low Level
• High Pressure, Low Pressure
• High Flow
• Low Flow
• Overload
• Underload
• Phase Loss
• Electrical Surges
Trend and Fault Data
The control system records and displays system operational data,
including flow rate, discharge pressure, motor amperage, and
system faults.
Remote Monitoring
Systems equipped with an ethernet switch and cellular modem
enable users to control and monitor the system from any web
browser.
These systems can also automatically send faults and warnings via
email or text message.
THEORY OF OPERATION
Precision Pumping Systems
•
GoPPS.com
•
6515 Business Way, Boise, ID 83716
•
208.323.5300
41
Can the Jockey Pump meet the setpoint?
NO
YES
Can the Lead Pump meet the setpoint?
6.2 Theory of Operation — MULTI PUMP
The system is designed to maintain the discharge Pressure
Setpoint.
A pump is turned on when the system pressure drops to the Wake-
Up Setpoint (Wake PSI), a specific amount of pressure below the
pressure setpoint.
A variable frequency drive (VFD) will operate the pump so that the
pressure setpoint is constantly maintained—slowing it down and
speeding it up as needed to meet fluctuating demands.
The pump will stop (enter sleep mode) when the system pressure
setpoint is reached and demand stops. Demand is measured by
using either the flow rate or the pump speed (indicated by VFD
frequency).
6.2.1 Pump Sequencing and Alternation
6.2.1a Lead-Lag Pump Sequencing
The pump station meets varying levels of demand by
controlling pump speed, as well how many pumps operate.
The PLC determines demand by measuring the system
pressure. If the pressure drops below the system pressure
setpoint, then the PLC will operate a pump, or multiple pumps,
until the system pressure reaches the setpoint.
First, the PLC uses the jockey pump to meet low demands. If it
can’t meet demand, then the lead pump is turned on, operating
at varying speeds to maintain the pressure setpoint. If the lead
pump is operating at full speed—and the pressure is still below
setpoint—then the lag pump is turned on (across-the-line),
operating at full speed.
Figure 1, below, describes pump sequence logic.
Jockey-Lead-Lag Pump Sequencing
JOCKEY: Sleep
JOCKEY: Variable
LEAD: Variable Speed
LEAD: Sleep
LAG: Sleep
LAG: Sleep
JOCKEY: Sleep
JOCKEY: Sleep
LEAD: Variable Speed
LEAD: Variable Speed
LAG: Full Speed
LAG: Sleep
