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 3.88 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 3.89 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 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
or
parameter 4-12 Motor Speed Low Limit
, to the
parameter 4-13 Motor Speed High
or
, 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 3.90 Staging Threshold
NOTICE
If the setpoint is reached after staging before the
variable speed pump reaches its minimum speed, the
system enters the state closed loop when the feedback
pressure is crossing the setpoint.
Parameter Description
VLT
®
AQUA Drive FC 202
212
Danfoss A/S © 05/2018 All rights reserved.
MG20OB02
3
3
Summary of Contents for VLT AQUA Drive FC 202
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