Danfoss VLT, Programming Manual

Page: 173 / 231

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 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.
175ZA640.10
F
min
F VLT pump
De-stage
timer period
Pump
switch-off
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 -
120.0 s] When adding a fixed speed pump controlled
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
.
25-41 Ramp Up Delay
Range: Function:
2.0 s
*
[0.0 -
12.0 s] When removing a fixed 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
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 .
Speed
Time
Fixed speed pump
(controlled by soft starter)
Lead pump starts
to ramp down
Cascade Controller
calls for another
pump
Cascade Controller
prepares for
removing pump
Lead pump starts
to ramp up
Time
Speed
Lead pump
(controlled by freq. conv.)
Staging Destaging
Fixed speed pump
(controlled by soft starter)
Lead pump
(controlled by freq. conv.)
t1
P 25-40 P 25-41
t2
130BA365.10
25-42 Staging Threshold
Range: Function:
Size related
*
[0 - 100 %]
Seconds
Variable speed
pump
Fixed speed
pump
Motor speed
high limit
Staging speed
Motor speed
low limit
4 5 0
130BA366.10
NOTE
If the set-point is reached after staging before the variable
speed pump reaches its minimum speed - the system will
enter the state closed loop as soon as the feedback pressure
is crossing the set-point.
Parameter Description
VLT
®
HVAC Drive Programming Guide
172 MG.11.CB.02 - VLT
®
is a registered Danfoss trademark
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