Speed
Time
Fixed speed pump
(controlled by soft starter)
Lead pump starts
to ramp down
Cascade Controller
calls for another
pump
Staging
Lead pump
(controlled by freq. conv.)
t
1
P 25-40
130BC371.10
Illustration 3.82 Staging
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 3.83 Destaging
NOTICE
Fixed pumps connected with star-delta starters are
staged in the same way as pumps connected with soft
starters. They are destaged in the same way as pumps
connected directly to mains.
25-42 Staging Threshold
Range: Function:
Size
related*
[ 0 - 100 %] When adding a xed-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
xed-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 xed-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 3.84 Staging Threshold
Parameter Descriptions Programming Guide
M0010001 Danfoss A/S © 10/2019 All rights reserved. 241
3 3
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