Parameter used
Speed at
Design Point
KNOWN
Speed at
Design Point
UNKNOWN
Cascade Controller
+
+
+
22-81 Square-linear Curve Approximation
+
+
-
+
+
-
+
+
-
22-85 Speed at Design Point [RPM]
+
-
-
22-87 Pressure at No-Flow Speed
+
+
+
-
+
-
-
+
-
-
+
-
22-80 Flow Compensation
Option:
Function:
[0]
*
Disabled Set-Point compensation not active.
[1]
Enabled Set-Point compensation is active. Enabling this
parameter allows the Flow Compensated Setpoint
operation.
22-81 Square-linear Curve Approximation
Range:
Function:
100 %
*
[0 - 100 %] Example 1:
Adjustment of this parameter allows the
shape of the control curve to be adjusted.
0 = Linear
100% = Ideal shape (theoretical).
NOTE
Not visible when running in cascade.
Control Curve
(head)
(flow)
H
Q
130BA388.11
100%
P22-81 0%
22-82 Work Point Calculation
Option:
Function:
Example 1: Speed at System Design Working Point
is known:
A
130BA385.11
P22-85/22-86
Control Curve
H
MIN
H
DESIGN
Set Point
n
RA
TED
_
f
RA
TED
n
DESIGN
-
f
DESIGN
Q
(flow)
H
(head)
Par.:
22-83/
22-84/
22-87
From the data sheet showing characteristics for
the specific equipment at different speeds, simply
reading across from the H
DESIGN
point and the
Q
DESIGN
point allows us to find point A, which is
the System Design Working Point. The pump
characteristics at this point should be identified
and the associated speed programmed. Closing
the valves and adjusting the speed until H
MIN
has
been achieved allows the speed at the no flow
point to be identified.
Adjustment of
22-81 Square-linear Curve Approxi-
then allows the shape of the control curve
to be adjusted infinitely.
Example 2:
Speed at System Design Working Point is not
known: Where the Speed at System Design
Working Point is unknown, another reference
point on the control curve needs to be
determined by means of the data sheet. By
looking at the curve for the rated speed and
plotting the design pressure (H
DESIGN
, Point C) the
flow at that pressure Q
RATED
can be determined.
Similarly, by plotting the design flow (Q
DESIGN
,
Point D). the pressure H
D
at that flow can be
determined. Knowing these two points on the
Parameter Description
VLT
®
HVAC Drive Programming Guide
156
MG.11.CC.02 - VLT
®
is a registered Danfoss trademark
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