Xylem IM255 AQUAVAR Intelligent Pump Controller - Manual (Page 78)

Figure 32: Flow compensation when speed at system design working point is known
Table 21: Flow compensation parameters when speed at design point is known
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 Disabled — speed at the design point
is known
22–84 Speed at No Flow [Hz] To find this point, close all of the
discharge valves in the system and
briefly run the pump at the minimum
design head. The speed
corresponding to the minimum head
requirement at no flow will be
entered here.
22–86 Speed at Design Point [Hz] These setpoints correspond to the
speed required to maintain point B
(design head {[20–21] Setpoint) and
design flow)
22–87 Pressure at No Flow System pressure at no flow and no
flow speed. This is the minimum
design head.
If the speed at the design point is unknown, the [22-82] Work Point Calculation must be
enabled. With the [22-82] Work Point Calculation enabled the controller will calculate the
speed at the design point based on settings of some additional parameters correlating to
the points shown on the diagram below. The first point determined is point A which is the
minimum required head at minimum speed ([22-84] Speed at No Flow [Hz] and [22-87]
Pressure at No-Flow Speed). Points C and D can be determined by consulting the pump
performance curve. Point C is determined by extending the design [20-21] Setpoint line
horizontally to intersect the rated curve which is the pump performance curve at rated
speed (usually 50 or 60Hz). The flow at this point (Q
Rated
) is set in [22-90] Flow at Rated
Speed. Point D is determined by extending the design flow point (Q
Design
) vertically to
intersect the rated speed curve. The head generated at this flow and speed is set at
[22-88] Pressure at Rated Speed. Knowing points A, C and D allow the controller to
calculate point E along with the control curve which includes point B (speed, pressure and
flow at design speed). Refer to the diagram below.
Operation
76 Aquavar ® Intelligent Pump Controller INSTRUCTION MANUAL