Xylem 19 001 351R2 PACE Integrated Pump Controller Human Machine Interface (HMI) for the Silent Storm VFD Pumping System – User Guide - Manual (Page 26)

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Filter A device used downstream of the pumps to clean the water being pumped
into the irrigation. These devices are typically self-cleaning, but require
hardware/software to self-clean.
Fixed speed Pumps run at a fixed RPM, defined by the motor windings and the frequency
of the line voltage (50/60 Hz).
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.
HSS High speed switching. Starting pumps with a VFD to reduce inrush current
and provide pressure control, but able to switch over to fixed speed so that
the VFD is able to start another pump.
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.
Lag pump A pump used later in the pump sequence to support increasing irrigation
demand requirements. The term lag simply refers to the fact that it does not
start first.
Lake fill (LLC) A circuit designed to keep a pond or lake at or above some minimum
level of water.
Lead pump The pump in a lead group which is chosen by the controller to start first. This
is usually determined by finding the pump in the lead group with the lowest
run-time.
Lockout A system which limits the pump systems available pumps and or limits the
speed of a variable speed pump during user-defined time of day or day
of week.
Low level probe A device that “shorts” out when removed from water. This removes the signal
from the PLC and tells it that the pump is not safe to run due to a low water
level condition.
Main pumps The pumps which are relied on for supplying the irrigation at mid-high
flow rates.
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.
Overpressure accumulator A counter that is used to determine the lag pump shut down sequence.