Danfoss VLT Programming Manual page 151

Parameter Description
3.20.7 22-8* Flow Compensation
It is sometimes the case that is not possible for a pressure transducer to be placed at a remote point in the system and it can
only be located close to the fan/pump outlet. Flow compensation operates by adjusting the set-point according to the output
frequency, which is almost proportional to flow, thus compensating for higher losses at higher flow rates.
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H (Required pressure) is the setpoint for closed loop (PI)
DESIGN
operation of the frequency converter and is set as for closed
loop operation without flow compensation.
It is recommended to use slip compensation and RPM as unit.
NOTE
When flow compensation is used with the Cascade
Controller (parameter group 25-**), the actual set-point will
not depend on speed (flow) but on the number of pumps
cut in. See below:
There are two methods which can be employed, depending upon whether or not the Speed at System design Working Point is
known.
150
®
VLT HVAC Drive Programming Guide
H
(head)
H
DESIGN
Set Point
H
MIN
P22-87
1
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MG.11.CB.02 - VLT is a registered Danfoss trademark
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Number of pumps