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Instruction Manual
45
Pump Alternation Control
Applications (
Altern
)
For pump control applications where two or more
similar pumps are used to control the level of a tank
or a well, it is desirable to have all the pumps operate
alternately. This prevents excessive wear and
overheating of one pump over the lack of use of the
other pumps.
Up to 8 relays can be set up to alternate every time
an on/off pump cycle is completed. The set points and
reset points can be programmed, so that the first
pump on is the first pump off.
Application #1: Pump Alternation
Using Relays 1 & 2
Set and Reset Point Programming
Relay
Set Point
Reset Point
Function
1
30.000
10.000
Controls
pump #1
2
35.000
5.000
Controls
pump #2
3
4.000
9.000
Controls
low alarm
4
40.000
29.000
Controls
high alarm
1. Relays 1 and 2 are set up for pump alternation.
2. Relays 3 and 4 are set up for low and high alarm
indication.
Pump Alternation Operation
1. Pump #1 turns on when the level reaches
30.000, when level drops below 10.000 pump #1
turns off.
2. The next time the level reaches 30.000, pump #2
turns on, when the level drops below 10.000,
pump #2 turns off.
3.
If the level doesn’t reach 35.000 pump #1 and
pump #2 will be operating alternately.
4. If pump #1 cannot keep the level below 35.000
pump #2 will turn on at 35.000, then as the level
drops to 10.000 pump #1 turns off, pump #2 is
still running and shuts off below 5.000.
5. Notice that with the set and reset points of pump
#2 outside the range of pump #1, the first pump
on is the first pump to go off. This is true for up to
8 alternating pumps, if set up accordingly.
6. Relay #3 will go into alarm if the level drops
below 4.000 and relay #4 will go into alarm if the
level exceeds 40.000.
7. Adding the 4 external relays expansion module
allows using the 4 SPDT internal relays for pump
alternation and the 4 SPST external relays for
high, high-high, low, and low-low alarm
indication.
Setting Up the Interlock Relay
(Force On) Feature
Relays 1-4 can be set up as interlock relays. To set
up the relays for the interlock feature:
1. Access the
Setup
–
Relay
–
Action
menu and set
the action to off.
2. In the Advanced features
–
User
menu, program
any of the digital inputs to
Force On
any of the
internal relays (1-4). The Advanced Features
Menu can be found on page 48.
3. Connect a switch or dry contact between the +5V
terminal and the corresponding digital input (dI-1
to dI-4) terminal.
Interlock Relay Operation Example
Relays 1 & 2 are configured to energize (their front
panel LEDs are steady on) when SW1 & SW2
switches (above) are closed. If the contacts to these
digital inputs are opened, the corresponding front
panel LEDs flash, indicating this condition. The
processes being controlled by the interlock relay will
stop, and will re-start only after the interlock relay is
re-activated by the digital inputs (switches).
Note: If multiple digital inputs are assigned to the
same relay, then the corresponding logic is (AND)
–
i.e. both switches must be closed to trip the relay.
1
2
3
4
5
6
+5
I1
I2
I3
I4
O1
7
8
O2
O3
9
10
O4
G
DI 1-4
DO 1-4
5 VDC
GND
SW2
SW1
