Model PD6000 Analog Input Process Meter Instruction Manual
54
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 overheat-
ing 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
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.
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
Pump Alternation Operation
1. Pump #1 turns on when level reaches 30.000, when level drops
below 10.000 pump #1 turns off.
2. The next time level reaches 30.000, pump #2 turns on, when 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 op-
erating 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 setup 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.
