KSB PumpDrive 2 - Switching Limits of a Running Pump in a Multiple Pump System; Start Speed; Start Flow Rate; Low Flow Limit

8 Commissioning/Shutdown
85 of 212
PumpDrive 2
H
2
Q
3-7-3-5
3-7-3-3
3-7-3-4
3-2-2-1
3-4-3-30
1
Fig.61: Switching limits of a running pump in a multiple pump system
1 Characteristic head curve of a running pump
2 Characteristic head curve of two running pumps
Stop limits: Stopping a running pump
Start limits: Starting the second pump
Arrows Effective direction of the switching limits
Coloured area Operating range of a running pump
Start Speed (3-7-3-3):
If the speed of a pump exceeds this value, an additional pump is started if available.
The diagram shows the start speed (3-7-3-3) plotted as a curve that limits, or restricts,
the operating range of the single pump. Above or to the right of this line, two
pumps are running. If the start speed (3-7-3-3) is also plotted as a curve, see the
"Switching limits of two running pumps in a multiple pump system" diagram, which
limits, or restricts, the operating range of two running pumps. Above or to the right
of this line, three pumps are running.
Start Flow Rate (3-7-3-5):
The start flow rate defines a point on the characteristic head curve where an
additional start limit intersects. It limits the operating range of the single pump.
Below or to the right of this line, two pumps are running. The start flow rate
optimised for efficiency equates to approximately 95% of the maximum flow rate
(factory setting) for most pumps.
Low Flow Limit (3-4-3-30):
When the low flow limit is reached, a (one) pump is stopped. Even if only one pump
is running, it is stopped provided that standby mode (sleep mode) is active
(ðSection8.8.4.2,Page103) . If standby mode is not active, the last pump is not
stopped. A warning message is output, however.
Stop Speed (3-7-3-4):
When the stop speed is reached, a (one) pump is stopped. Even if only one pump is
running, it is stopped provided that standby mode (sleep mode) is active.
(ðSection8.8.4.2,Page103) If standby mode is not active, the last pump is not
stopped. The minimum speed (3-2-2-1) cannot be undershot, however.
The "Switching limits of two running pumps in a multiple pump system" diagram
shows the switching limits of two running pumps in a multiple pump system and the
associated parameters in the head/flow rate diagram.