Vega VEGAMET 841 Operating page 40

10 Applications and functions
Option Dry weather pump
40
Rel. 3: 90% On
Rel. 2: 75% On
Rel. 1: 60% On
Rel. 1..3: 10% Off
Rel. 1
Rel. 2
Rel. 3
Rel. no. 1 2
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.
Fig. 19: Example of a pump control with option "Dry weather pump"
Note:
If the option "Dry weather pump" is activated, only the mode "Alternat-
ing pump operation" will be available, i.e. only one pump at a time is
in operation.
3 1 2 3 1 2 3 1 2
VEGAMET 841 • 4 ... 20 mA
t(h)