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Example 3 Reservoir Control (pump up)
A reservoir is typically used to temporarily hold liquid, and when the level
reaches a specific low point, the reservoir is pumped up.
In this example, there are two pumps, which will be set to alternate duty
assist, so they come on alternately. Pump 1 is to be set to relay 1, pump 2 to
relay 2, and the low-level alarm to relay 3.
This will operate as follows:
During normal operation, pump 1 will come on at 1.96 m, and pump up to
2.24 m. The setpoints are then shifted to pump 2, which will come on first
next time.
During peak periods, when pump 1 cannot cope, pump 1 will come on at
1.96 m, pump 2 will come on at 1.4 m and pump up to 2.24 m. The
setpoints are then shifted to pump 2, which will come on first next time.
If both pumps cannot cope, and the level falls to 0.28 m, then the alarm relay
(relay 3) will come on, and go off when the level rises to 0.42m. This will
indicate insufficient capacity of the pumps.
The display will show the level in the sump and the mA output will be
representative of level where 4mA = empty level (0%) and 20mA = 2.8m
(100%)
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