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Alternating & Duplexing Relays Alternating & Duplexing Relays Alternating & Duplexing Relays
Low Voltage Products & Systems
13.3
1105S
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Alternating & Duplexing Relays
Alternating & Duplexing Relays
Alternating & Duplexing Relays
Alternating & Duplexing Relays
Alternating & Duplexing Relays
Application Notes
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T
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Typical Connection Diagram
ypical Connection Diagram
ypical Connection Diagram
ypical Connection Diagram
ypical Connection Diagram
Timing Diagram
Timing Diagram
Timing Diagram
Timing Diagram
Timing Diagram
Many dual pump, duplex pumping applications, require two or more
float switches to properly operate the system. The ARP Series of
alternating (duplex or cross wired) relays are designed to equalize
run time for two loads by automatically changing the lead pump
and lag pump sequence at the end of each cycle. The ARP
assures approximately equal wear on both loads, plus the
duplexing models allow both pumps to operate simultaneously.
This application can be used for water and wastewater pumping;
and for circulating and distribution pumping of various liquids.
The diagram depicts a typical drain pumping application. The
OFF, Lead and Lag float switches are connected as shown. As the
liquid level rises, first the OFF and then the lead float switches
close; pump 1 energizes. The liquid is pumped down by pump
1 until the OFF switch opens because of the latching action of
the P1 auxiliary contacts on the pumps contactor. As the OFF
switch opens, pump 1 turns OFF and the ARP toggles making
pump 2 the lead pump. This operation continues with the pumps
alternating lead/lag order on each successive cycle. If the flow is
too heavy for one pump, the lag float switch eventually closes.
Now, both pumps operate until the OFF float switch opens. A
benefit of this connection method is the elimination of rapid cy-
cling of the pump motors caused by float switch bounce.
Duplex Panel with Latching Pump Down Operation
Duplex Panel with Latching Pump Down Operation
Duplex Panel with Latching Pump Down Operation
Duplex Panel with Latching Pump Down Operation
Duplex Panel with Latching Pump Down Operation
Alternating:
Alternating:
Alternating:
Alternating:
Alternating: Power must be applied at all times. When the level in
the tank rises to the normal level, the Lead Float Switch closes.
Pump A is turned on via Pump A contactor, and will remain in
this condition until the Lead Float Switch opens. When the Lead
Float Switch opens, the ARP relay contacts transfer. When the
level in the tank rises again to the normal level, the Lead Float
Switch closes, energizing Pump B via Pump B contactor. Pump
B will remain energized until the Lead Float Switch opens. The ARP
relay contacts then transfer back to their original position. The ARPs
internal relay contacts transfer each time the Lead Float Switch opens.
By alternating the lead pump for each successive operation, the total
number of operating hours is similar.
Duplexing:
Duplexing:
Duplexing:
Duplexing:
Duplexing: When an Alternating Relay is internally cross wired,
the normal alternating operation is extended to include
duplexing. If the Lead Float Switch cycles as previously ex-
plained, normal alternating operation will occur. If the Lead
Float Switch and the Lag Float Switch close simultaneously,
due to a heavy flow into the tank, both pumps A & B will be
energized. The ability to alternate the pumps during normal
work loads and then operate both when the load is high is
called Duplexing. Duplexing relays can save energy in most
systems because only one smaller pump is operating most of
the time; yet the system has the capacity to handle twice the
load.