38
10 Applications and functions
VEGAMET 342 • 4 … 20 mA
63731-EN-221107
•
Relay 2 upper switching point = 75.0 %
•
Relay 2 lower switching point = 10.0 %
•
Relay 3 upper switching point = 90.0 %
•
Relay 3 lower switching point = 10.0 %
The function of pump control 4 is shown in detail in the following dia-
gram. The previously described example is used as a basis.
Rel. 1: 60% On
Rel. 1..3: 10% Off
Rel. 2: 75% On
Rel. 3: 90% On
t(h)
Rel. 3
Rel. no.
Rel. 2
1 2
3
1
2
3
1
2
3 1 2
Rel. 1
Fig. 18: Example of pump control 4
Pump control 2/4 with dry weather pump is used to protect e.g.
rain retention basins with different sized pumps against overfilling.
Normally (in fair weather), a pump with low capacity (dry weather
pump) is sufficient to maintain the level in the retention basin at a
safe level (Hi-Level). If heavy rainfall causes an increased inflow, the
fair weather pump can no longer maintain the level. In such cases, a
larger pump is switched on when the HiHi level is exceeded and the
dry weather pump is switched off. The large pump then remains in
operation until the switch-off point is reached. If the level rises again,
the dry weather pump switches back on first.
There is also the possibility of using multiple large pumps in alternat-
ing mode. The algorithm for the switching function is then determined
by the pump control mode.
Option Dry weather pump
