25-26 Destage At No-Flow
Option: Function:
This parameter ensures that when a no-ow
situation occurs, the xed speed pumps are
destaged 1 by 1 until the no-ow signal
disappears. This requires that no-ow detection is
active. See parameter group 22-2* No-Flow
Detection.
If [0] Disabled is selected, the cascade controller
does not change the normal behavior of the
system.
[0] * Disabled
[1] Enabled
25-27 Stage Function
Option: Function:
If the stage function is set to [0] Disabled,
parameter 25-28 Stage Function Time is not
activated.
[0] Disabled
[1] Enabled
25-28 Stage Function Time
Range: Function:
15
s*
[0 -
300 s]
The stage function time is programmed to avoid
frequent staging of the xed speed pumps. The
stage function time starts if it is [1] Enabled by
parameter 25-27 Stage Function, and when the
variable speed pump runs at motor speed high
limit, parameter 4-13 Motor Speed High Limit [RPM]
or parameter 4-14 Motor Speed High Limit [Hz], with
at least 1 xed speed pump in the stop position.
When the programmed value of the timer expires, a
xed speed pump is staged.
25-29 Destage Function
Option: Function:
The destage function ensures that the lowest
numbers of pumps are running to save energy and
to avoid dead head water circulation in the
variable speed pump. If the destage function is set
to [0] Disabled, parameter 25-30 Destage Function
Time is not activated.
[0] Disabled
[1] Enabled
25-30 Destage Function Time
Range: Function:
15
s*
[0 -
300 s]
The destage function timer is programmable to
avoid frequent staging/destaging of the xed speed
pumps. The destage function time starts when the
adjustable speed pump is running at
parameter 4-11 Motor Speed Low Limit [RPM] or
parameter 4-12 Motor Speed Low Limit [Hz], with 1 or
more xed speed pumps in operation and system
25-30 Destage Function Time
Range: Function:
requirements satised. In this situation, the
adjustable speed pump contributes a little to the
system. When the programmed value of the timer
expires, a stage is removed, avoiding dead head
water circulation in the adjustable speed pump.
e75za640.12
(4-12)
(27-27)
F
min
F
VLT pump
Destage
timer period
Pump
switch-off
Illustration 3.87 Destage Function Time
3.22.3 25-4* Staging Settings
Parameters determining conditions for staging/destaging
the pumps.
25-40 Ramp Down Delay
Range: Function:
10 s* [0 -
120 s]
When adding a xed speed pump controlled by
a soft starter or a star-delta starter, it is possible
to delay the ramp down of the lead pump until
a preset time after the start of the xed speed
pump. This delay eliminates pressure surges or
water hammer in the system.
Use this option only if [1] Soft Starter or [2] Star
Delta is selected in parameter 25-02 Motor Start.
25-41 Ramp Up Delay
Range: Function:
2 s* [0 -
12 s]
When removing a xed speed pump controlled by
a soft starter, it is possible to delay the ramp up of
the lead pump until a preset time after the stop of
the xed speed pump. This delay eliminates
pressure surges or water hammer in the system.
Only to be used if [1] Soft Starter is selected in
parameter 25-02 Motor Start.
Parameter Description Programming Guide
MG20OB02 Danfoss A/S © 05/2018 All rights reserved. 211
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