Xylem 19 001 251 R3 Floboy VFD Pumping System - Manual (Page 37)

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Foot valve A device used primarily on horizontal lift applications to maintain pump prime.
Frequency (Hz) The number of oscillations per second of any system. Typically used to
refer to electrical systems, such as AC power line frequency, or variable speed
drive output frequency. This frequency defines the speed of an AC motor.
GPM Gallons per minute. Units of flow for US use.
Input A way for a control system to detect real-world occurrences. These can be
digital or analog.
Inverter Another term for Variable Frequency Drive (VFD). Actually, more correctly
applied to the output circuitry of the drive, which converts DC voltage to AC
voltage.
Lift This refers to how high water must be "lifted" to reach the pump suction. Lift
stations have even harsher NPSHR than Flooded Suction systems. Loss of
prime safety is an excellent choice for these systems. Auto-re-prime systems
are available to help maintain a full suction line (CRD reprime, vacuum pumps).
Must-run time The amount of time (in seconds) that the pump must run.
Output A way for a control system to generate real world actions. An output can be a
120VAC signal to turn on a pump, or a varying 4-20 mA signal to control the
speed of a VFD. Many types of output are available.
Overload A condition in which pumps are allowed to produce more flow rate than the
motor that drives them is designed for. Also refers to a device in the control
panel, which detects this situation and stops the pump in order to protect it.
Over-pressure accumulator A counter that is used to determine the lag pump shut down sequence.
Overshoot Indicates that the control variable has exceeded the set point value while the
controller was trying to correct it.
PM pump Pressure Maintenance Pump. Handles very light flow rates and leaks to
prevent the main pumps from cycling.
Pressure reducing valve (PRV) A control valve designed strictly for maintaining a specific downstream
pressure.
Pressure switch This is a normally open or normally closed switch that changes output state
when the pressure exceeds the set point of the switch.
Pressure transducer A device that converts actual pressure to a 4-20 mA signal that is input into the
PLC which converts it back to an actual pressure reading.
PSI Pounds per square inch. Units of pressure for US use.
Re-arming This refers to turning the pertinent individual pump switch to the OFF position
and then back to the On position to clear an individual pump fault.
Register A memory location in a PLC. These can be used as configuration and storage
or temporary storage during mathematical calculations.
Relay This is a normally open or normally closed device that changes output state
when it is energized or de-energized and sends or removes a 120VAC signal to
the PLC.
Set point The desired situation for a control variable. If the user wanted the irrigation
system to operate at 120 PSI, that would be the set point for the controller.