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Chapter 6: Pump Control
The Skymetry WTU-14 can be used in Fill or Drain pump control
applications using either float switches or an analog level transduc-
er. When used with Float Switches, dry contact inputs #6-8 have a
dedicated special function (see below):
Pump Control using Float Switches
Dry Contact Input #6 – Lead pump float switch
Dry Contact Input #7 – Lag pump float switch
Dry Contact Input #8 – Pumps-off float switch
When performing pump control using an analog level transducer
(4–20mA), analog input #6 is designated as the well level input.
Note: Only normally-open float switches can be
used for pump control (e.g. the switch is open when
no water is present).
How it works—Float Switches
When performing drain pump control using float switches, three
floats are required: Lead, Lag, and Pumps-Off (see Fig 1). The Lead
float determines when to turn on the first pump. If the first pump
is unable to bring the level below the Pumps-Off float, then the Lag
float will close, turning on the second pump. When the level drops
below the Pumps-Off float, both pumps are turned off. If any of
the floats get stuck (i.e. the lead and pumps-off floats closed, or the
lag and pumps-off floats closed) then both pumps will be turned on
and an alarm will be tripped on the output or outputs in question. In
duplex mode, the WTU-14 will automatically alternate between the
two pumps to facilitate uniform run time between the two.
If only one relay output is set to pump-control mode, then simplex
control is performed. In Simplex mode only the Lead float (Dry
Contact #6) and Pumps-Off float (Dry Contact #8) are required.
Either output relay can be used in simplex mode.
Chapter 6: Pump Control
53
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