Vega VEGAMET 841 Operating page 39

Functional principle
Example
VEGAMET 841 • 4 ... 20 mA
Application example pump control 3/4
Pump control 3/4 is used to control several pumps with the same
function alternately and in a fixed sequence. In case of increased
pumping requirement, all pumps can also run at the same time, in
dependence on the entered switching points. This measure achieves
an even utilization of the pumps and increases operational reliability.
All relays with activated pump control are not assigned to a certain
switching point but are switched on and off alternately. When a switch-
on point is reached, the controller selects the relay that is next in the
sequence. When a switch-off point is reached, the relays are switched
off in the sequence they were switched on.
This pump control system offers two different options:
•
Pump control 3: The upper switching point determines the switch-
off point for the relay, whereas the lower switching point deter-
mines the switch-on point
•
Pump control 4: The upper switching point determines the switch-
on point for the relay, whereas the lower switching point deter-
mines the switch-off point
The sequence cannot be changed, the relay with the lowest index is
switched on first, then the relay with the next higher index. After the
relay with the highest index, the relay with the lowest index follows, for
example Rel. 1 -> Rel. 2 -> Rel. 3 -> Rel. 1 -> Rel. 2 ...
The sequence applies only to those relays assigned to the pump
control.
In a waste water disposal system, a sump should be pumped empty
when a certain level is reached. Three pumps are available for this. At
60 % level, pump 1 should run until the level has fallen below 10 %.
If the 60 % point is exceeded again, the same task is transferred to
pump 2. In the third cycle, pump 3 is activated; after that, pump 1
again. If the level continues to rise despite operation of a pump, an
additional pump switched on when the level exceeds the 75 % switch-
ing point. And if the level still rises further due to extreme inflow and
exceeds the 90 % limit, pump 3 is also switched on.
For relay 1 ... 3, the mode of operation "Pump control 4" is adjusted
with the option "Sequenced operation". The relay switching points are
configured as follows:
Select in the DTM navigation section the menu items "Meas. loop -
Outputs - Relay".
•
Relay 1 upper switching point = 60.0 %
•
Relay 1 lower switching point = 10.0 %
•
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.
10 Applications and functions
39