Danfoss VLT Series Programming Manual page 182

Parameter Description
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 Disabled [0], the 25-30 Destage Function
Time will not be activated.
[0] Disabled
[1] Enabled
*
25-30 Destage Function Time
Range: Function:
15 [0 - The Destage Function Timer is programmable to
s 300 s] avoid frequent staging/destaging of the fixed
*
speed pumps. The Destage Function Time starts
when the adjustable speed pump is running at
4-11 Motor Speed Low Limit [RPM] or 4-12 Motor
Speed Low Limit [Hz], with one or more fixed
speed pumps in operation and system
requirements satisfied. 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.
F VLT pump
Pump
switch-o
F
min
3.23.3 25-4* Staging Settings
Parameters determining conditions for staging/destaging
the pumps.
25-40 Ramp Down Delay
Range: Function:
10.0 s [0.0 - When adding a fixed speed pump controlled
*
120.0 s] by a soft starter, it is possible to delay the
ramp down of the lead pump until a preset
time after the start of the fixed speed pump
to eliminate pressure surges or water
hammer in the system.
Only to be used if Soft Starter [1] is selected
in 25-02 Motor Start.
®
VLT HVAC Drive Programming Guide
De-stage
timer period
®
MG.11.CC.02 - VLT is a registered Danfoss trademark
25-41 Ramp Up Delay
Range: Function:
2.0 s [0.0 - When removing a fixed speed pump controlled
*
12.0 s] by a soft starter, it is possible to delay the
ramp up of the lead pump until a preset time
after the stopping of the fixed speed pump to
eliminate pressure surges or water hammer in
the system.
Only to be used if Soft Starter [1] is selected in
25-02 Motor Start.
Staging
Speed
Fixed speed pump
(controlled by soft starter)
Lead pump
(controlled by freq. conv.)
t
Time
1
P 25-40
Lead pump starts
to ramp down
Cascade Controller
calls for another
pump
25-42 Staging Threshold
Range: Function:
Size [ 0 When adding a fixed speed pump, in order to
related - 100 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 4-11 Motor Speed Low Limit [RPM] or
4-12 Motor Speed Low Limit [Hz], to the
4-13 Motor Speed High Limit [RPM] or 4-14 Motor
Speed High Limit [Hz], expressed in percent.
Staging Threshold must range from
LOW
=
HIGH
STAGE %
to 100%, where n
and n is Motor Speed High Limit.
HIGH
Motor speed
high limit
Staging speed
Motor speed
low limit
0 4
Destaging
Speed
Lead pump
(controlled by freq. conv.)
Fixed speed pump
(controlled by soft starter)
t
Time
2
P 25-41
Lead pump starts
to ramp up
Cascade Controller
prepares for
removing pump
× 100 %
is Motor Speed Low Limit
LOW
Fixed speed
pump
Variable speed
pump
5
Seconds
181
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