Xylem IM255 AQUAVAR Intelligent Pump Controller - Manual (Page 79)

Figure 33: Flow compensation when speed at design working point is unknown
Table 22: Flow compensation parameters when speed at design point is unknown
Parameter Number Description Set to
22–80 Flow Compensation Enabled
22–81 Square-Linear Curve Approximation Modify between 100% (square) and
0% (linear) per system requirements.
22–82 Work Point Calculation Enabled — speed at design point is
unknown
22–84 Speed at No Flow [Hz] To find this point, close all valves in
the system and run the pump at the
minimum head. The speed
corresponding to the minimum head
requirement at no flow will be
entered here. Point A.
22–87 Pressure at No Flow System pressure at no flow and no
flow speed. This is the minimum
design head. Point A.
22–88 Pressure at Rated Speed This setting corresponds to the head
developed at design flow and rated
speed. This value can be defined
using the pump performance curve.
Intersects with the design flow to
form point D.
22–89 Flow at Design Point This setting corresponds to the
system design flow. Intersects with
the pressure at rated speed to form
point D and with the setpoint to form
point B.
22–90 Flow at Rated Speed This setting corresponds to the flow at
rated speed. This value can be
defined using the pump performance
curve. Intersects with the setpoint to
form point C.
Dual pump value increase
In a Duplex Control System the friction losses can increase when both the lead and lag
pumps are running due to the additional flow in the system. When both pumps are
running, the Rated Curve and Design Curve shown above will change (reach higher flows
at a given pressure) when compared to when a single pump is running. This means that
the settings given to configure the Flow Compensation function may not be accurate
when both pumps are running. The Dual Pump Value Increase setting applies an increase
to the setpoint which will offset the additional losses associated with both pumps running.
Operation
Aquavar ® Intelligent Pump Controller INSTRUCTION MANUAL 77