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Moeller Wiring Manual > All about Motors > Duplex pump control > Fully automatic control for two pumps
All about Motors
Duplex pump control

Fully automatic control for two pumps [t-head1-first]

Starting sequence of pumps 1 and 2 can be selected by control switch S12

Control circuit wiring with two float switches for basic and peak loads (operation is also possible with two pressure switches)

P1 Auto

=

Pump 1 constant load, Pump 2 peak load

P2 Auto

=

Pump 2 constant load, Pump 1 peak load

P1 + P2

=

Direct operation independent of float switches (or pressure switches)

 

 
     

Position 1Cable with float, counterweight, pulleys and clamps

Position 2Storage tank

Position 3Inlet

Position 4Pressure pipe

Position 5Outlet

 

Position 6Centrifugal or reciprocating pump

Position 7Pump 1

Position 8Pump 2

Position 9Suction pipe with filter

Position 10Well

Float switch F7 closes before F8
 
Q11: Pump 1 mains contactor
 
Q12: Pump 2 mains contactor
Method of operation
The duplex pump control is designed for operation of two pump motors M1 and M2. Control is via float switches F7 and F8.
Operating mode selector switch S12 in position P1 auto: The system operates as follows:
When the water level in the storage tank falls or rises, F7 switches pump 1 on or off (basic load). If the water level drops below
 
the range of F7 (discharge is greater than intake), F8 starts pump 2 (peak load). When the water level rises again, F8 is deactivated. Pump 2 continues running until F7 stops both pumps.
The operating sequence of pumps 1 and 2 can be determined using operating mode selector switch S12: Position P1 auto or P2 auto.
 
In position P1 + P2, both pumps are in operation, independent of the float switches (Caution! Tank may possibly overflow).
On the version of duplex pump control with automatic load sharing (T0(3)-4-15915), S12 has a further position: the sequence of operations is automatically reversed after each cycle.
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