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run-time.
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).
Lock-out
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.
OTIS
Operator Terminal Information System. Accesses PLC data, and displays it.
Also allows access to settable registers that you need to program.
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 setpoint value while the
controller was trying to correct it.
Phase monitor
A device that analyzes incoming voltage and determines whether all voltage
parameters are acceptable and the phase sequence is correct.
PLC
Programmable Logic Controller. A very robust/rugged computer designed for
equipment control in harsh environments.
PM pump
Pressure Maintenance Pump. Handles very light flow rates and leaks to
prevent the main pumps from cycling.
Pressure switch
This is a normally open or normally closed switch that changes output state
when the pressure exceeds the setpoint 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 on to clear an individual pump fault.
Register
A memory location in a PLC. These can be used as configuration and
