46
11 Applications and functions
VEGAMET 861 • 4 … 20 mA/HART
58866-EN-200401
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. 20: 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. 21: 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.
Option Dry weather pump
