Vega VEGAMET 391 Operating Instructions Manual page 49

Pump control mode
Option, forced switchover
VEGAMET 391 • 4 ... 20 mA/HART
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.
The pump control system offers the possibility to choose between
sequenced and alternating pump operation:
•
Sequenced operation: Depending on the switching points, all
pumps are switched on one after the other, i.e. the max. number
of pumps that can be switched on corresponds to the number of
assigned relays
•
Alternating pump operation: Independent of the switching point,
only one pump at a time is switched on
If the level does not change over a longer period of time, the same
pump would remain switched on. Via the parameter "Changeover
time", a time period can be preset, after which a forced changeover of
the pump is carried out. This function is described under pump control
1/2.
8 Application examples
49