Work Point Calculation - Danfoss VLT HVACDrive Instruction Manual

VLT ® HVAC Drive Instruction Manual

22-82 Work Point Calculation

Option: Function:
Example 1: Speed at System Design Working Point is known:
From the data sheet showing characteristics for the specific equipment at different speeds, simply
reading across from the H point and the Q
DESIGN
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
achieved allows the speed at the no flow point to be identified.
Adjustment of par. 22-81 Square-linear Curve Approximation
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 , Point C), the flow at that pressure Q
DESIGN
design flow (Q , Point D), the pressure H
DESIGN
points on the pump curve, along with H
to calculate the reference point B and thus to plot the control curve that will also include the system
design working point A.
MG.11.AB.22 - VLT ® is a registered Danfoss trademark
7 How to Program the Adjustable Frequency
point allows us to find point A, which is the
DESIGN
then allows the shape of the control
can be determined. Similarly, by plotting the
RATED
at that flow can be determined. Knowing these two
D
described above, allows the adjustable frequency drive
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has been
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