Operating instructions

22-76 Interval between Starts
Range: Function:
Application
dependent
*
[Application
dependant]
Sets the time desired as minimum
time between two starts. Any
normal start command (Start/Jog/
Freeze) will be disregarded until
the timer has expired.
22-77 Minimum Run Time
Range: Function:
0 s * [Application
dependant]
Sets the time desired as minimum run time
after a normal start command (Start/Jog/
Freeze). Any normal stop command will be
disregarded until the set time has expired. The
timer will start counting following a normal
start command (Start/Jog/Freeze).
The timer will be overridden by a Coast
(Inverse) or an External Interlock command.
NOTE
Does not work in cascade mode.
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.
H
DESIGN
(Required pressure) is the setpoint for closed loop (PI)
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.
Parameter used
Speed at
Design Point
KNOWN
Speed at
Design Point
UNKNOWN
Cascade Controller
Flow Compensation, 22-80 + + +
Square-Linear Curve Approximation, 22-81 + + -
Work Point Calculation, 22-82 + + -
Speed at No Flow, 22-83/84 + + -
Speed at Design Point, 22-85/86 + - -
Pressure at No Flow, 22-87 + + +
Pressure at Rated Speed, 22-88 - + -
Flow at Design Point, 22-89 - + -
Flow at Rated Speed, 22-90 - + -
Parameter Description
VLT
®
HVAC Drive Programming Guide
148 MG.11.CA.02 - VLT
®
is a registered Danfoss trademark
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