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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.
SCADA
Supervisory Control And Data Acquisition.
Sequential alternation
One of several methods of selecting which pump to use first. This method
simply picks #1 the first time, #2 the next and so on. Once all pumps have
been selected as "lead" once, the method starts over at #1.
Setpoint
The desired situation for a control variable. If the user wanted the irrigation
system to operate at 120 PSI, that would be the setpoint for the controller.
SO
2
Pump
Similar to a water feature pump in operation, but used to pump water through
a SO
2
burner to reduce the PH of the local irrigation water supply.
Submersible
A type of pump, some similar to a vertical turbine, others are of a different
configuration, but in all cases the motor and pump are close-coupled and
actually located in the wet-well, sump or bore hole. In fact, most of these
pumps must be covered with water to operate without overheating. The
motors used on these pumps are typically less efficient than those used on
vertical turbine or centrifugal pumps. Submersible pumps require more water
over the pump suction than do turbines; therefore the low water level safety
must be carefully set high enough to protect these pumps.
Speed test
The method used to shut down a VSP during normal automatic operation.
Temperature switch
This is a normally open or normally closed switch that changes output state
when the temperature exceeds the setpoint of the switch.
Timed alternation
One of several methods of selecting which main pump to use first. This
method determines which pump to start first, second, etc by picking the pump
with the least run time.
Transfer pump
A pump designed to move water from one reservoir to another.
Units
Gives context to numbers in the PLC. Units describe what the number is
about, such as PSI, GPM.
VFD
Variable frequency drive. This allows a pump to run at variable speeds.
VSP
Variable speed pump. Refers to a pump being controlled by the variable
frequency drive. In the case of pump systems, variable speed gives the
controller the ability to change the output of the station by changing the
speed of one or more pumps.
Vertical turbine
A type of pump which has the motor at the top, and the pump hanging on a
column of pipe into a wet-well or “bore hole.” These pumps are very efficient
and come in a wide range of horsepower/flow/pressure combinations. These
pumps are generally not capable of high lift on the suction side. These pumps
can be installed in a container, called a “Can”, which allows the pump to be
used in-line as a booster. Low Level safety is used on Vertical Turbine sets,
can turbines require low inlet pressure, or loss of prime safeties.
Water feature pump
These pumps (of any type) are typically used to pump water through a piping
system separate from the irrigation in order to operate man-made creeks,
waterfalls, fountains etc. These pumps are usually run strictly by timers or
interface relays (See also, lock-out).
