Danfoss VLT HVAC Drive FC 102, Programming Manual, Page: 197 / 250

Cascade Controller
prepares for
removing pump
Lead pump starts
to ramp up
Time
Speed
Lead pump
(controlled by freq. conv.)
Destaging
Fixed speed pump
(controlled by soft starter)
P 25-41
t
2
130BC372.10
Illustration 3.77 Destaging
25-42 Staging Threshold
Range: Function:
Size
related
*
[ 0 -
100
%] When adding a fixed speed pump, to prevent
an overshoot of pressure, the variable speed
pump ramps down to a lower speed. When
the variable speed pump reaches the “Staging
Speed” the fixed speed pump is staged on.
The staging threshold is used to calculate the
speed of the variable speed pump when the
“cut-in point” of the fixed speed pump occurs.
The calculation of the staging threshold is the
ratio of
parameter 4-11 Motor Speed Low Limit
[RPM] or parameter 4-12 Motor Speed Low Limit
[Hz] , to the parameter 4-13 Motor Speed High
Limit [RPM] or parameter 4-14 Motor Speed
High Limit [Hz] , expressed in percent.
Staging threshold must range from
STAGE %
=
LOW
HIGH
× 100 %
to 100%, where n
LOW
is motor speed low limit
and n
HIGH
is Motor Speed High Limit.
Seconds
Variable speed
pump
Fixed speed
pump
Motor speed
high limit
Staging speed
Motor speed
low limit
4 5 0
130BA366.10
Illustration 3.78 Staging Threshold
25-43 Destaging Threshold
Range: Function:
Size
related
*
[ 0 -
100
%] When removing a fixed speed pump to
prevent an undershoot of pressure, the
variable speed pump ramps up to a higher
speed. When the variable speed pump
reaches the destaging speed, the fixed speed
pump is destaged. The destaging threshold is
used to calculate the speed of the variable
speed pump when the destaging of the fixed
speed pump occurs. The calculation of the
destaging threshold is the ratio of
parameter 4-11 Motor Speed Low Limit [RPM] or
parameter 4-12 Motor Speed Low Limit [Hz] , to
parameter 4-13 Motor Speed High Limit [RPM]
or parameter 4-14 Motor Speed High Limit [Hz] ,
expressed in percent.
Destaging threshold must range from
STAGE % =
LOW
HIGH
× 100 %
to 100%, where n
LOW
is
motor speed low limit and n
HIGH
is motor
speed high limit.
130BA367.10
3 5 0 1 Seconds
Variable speed
pump
Fixed speed
pump
Motor speed
high limit
Destaging
speed
Motor speed
low limit
Illustration 3.79 Destaging Threshold
Parameter Descriptions Programming Guide
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